Document 5kqwYB2V8bEVxenvGYnMb8o9V

FILE N A M E : C E R A M IC S (C E R ) DATE: 1935 DOC#: CER009 D O C U M E N T D E S C R IP T IO N : J o u rn a l A rtic le - M o d e r n V ie w s o n Silicosis 'Y PRESS 4 "ACO PRESS .es) CM1LLAN V, LTD. TH E JOURNAL OF HYGIENE _ EDITED BY GEORGE H. F. NUTTALL, M.D., Ph.D., Sc.D., LL.D., F.R.S. EMERITUS PROFESSOR OF BIOLOGY IN THE UNIVERSITY OF CAMBRIDGE IN CONJUNCTION WITH JOHN S. HALDANE, C.H., M.D., D.Sc., LL.D., F.R.S. LATE READER IN PHYSIOLOGY IN THE UNIVERSITY OF OXFORD J. C. G. LEDINGHAM, C.M.G., M.B., D.Sc., F.R.S. PROFESSOR OF BACTERIOLOGY IN THE UNIVERSITY OF LONDON, DIRECTOR OF THE LISTER INSTITUTE, LONDON G. S. GRAHAM-SMITH, M.D., F.R.S. READER IN PREVENTIVE MEDICINE, CAMBRIDGE MAJOR GREENWOOD, D.Sc., F.R.C.P. (L o n d .), F.R.S. PROFESSOR O r EPIDEMIOLOGY AND VITAL STATISTICS IN THE UNIVERSITY OF LONDON SIR DAVID MUNRO, K.C.B., C.I.E., M.B. SECRETARY, INDUSTRIAL HEALTH RESEARCH BOARD, MEDICAL RESEARCH COUNCIL VOLUME XXXV. 1935 CAMBRIDGE A T THE UNIVERSITY PRESS 193 5 i1 \ l Contents No. 2 (May 1935) 1 j PAG E I)A' Is; L J D i-zi>ak, ,J. S, ;U1(l F er n a n d o , F S Scarlatina I m m u nity m Hong Kong . . p j I G1 \ T aylor, G L and A dai r, Muriel E The Precipitation Reaction 169 1 Payi/ j r, G. L The Demonstration o f the I nci ea.e of Globulin in Diphtheria Antitoxins by the Precipitation Reaction , 174 4 I1OWNING, C. H. and G olbran. e n, R. Variation in Chemothera peutic Su.sccptibit}' associated uith Change in Virulence of a Strain of rnjjxinosoinn hrucci I mj van J,IS,IOE('K. Dr ft A If. Infia-ivd Radiation ami V m l Ob- ' t n a l i o n , (Wi th ,`i Eigine. m the d'ext) l s C o u v - R r s N , A Human Foot Pei.piration, it. X u t u i r ,,nd Inter- a< t ion. u 11h Ft >ot v ear < "OKI,, W hi M o d e r n l i m . on S i l w o . i . ( U n l i Plate-, i IV) do: C union, L o u a v n ; p The T e W n g of I W m f e e t a n t . ln , | ,, p H,M, 1(,. ol Organic .Matter (With ) Figun in the Text) 21 9 <;uisi;-v; H J an(l M r i i i , R O. A Study of the Stieptm oeei from f i f t y ( use. of Bocine Mastitis 238 Co ok r r r l l , O .J On the Et r or . Invoiced the \b termination of tooling Pouem and An Velocities with a K.Uu-TI . ;<um ter ! V ith a Futures HI t he Text i 200 ( ; UU) MK' A D an<l K V Vi AKUKt Mt x The Antimn-. ot the ( 'holera Grouji of Vila m-- 262 F rown, W. A. and A l u - on, V. I) ( Wri e r, and Return ( W e . in Scarlet Fever 2.83 I , U , A h - J ; and ( ; u i , l K - J S Tuberculin Reaction, on the ifong Kong Chine.e, with -pedal icfeienee to the u-e of ddiberetilo- protem , 3u0 ;j N o. 3 (August 1935) I H B edford, T The Ftl ective Radiating Surface of the Human B o d y 303 i B edford, I Skin Temperature in Relation to the Warmth of the f environment (With 2 Figures in tie Text) , 307 * BoyroTT.G. W M Prevention of Compressed Air Hint,.. Obsolete i Statutory Regulation, as an Obstacle to Progress . 31 S Herman. I' and T i n . Dioxide Bat!:, on W olff, G eorgi, f. C. Galloway, I. A and I fection by the Xo. W hi te , P B r i t e The Cruick. ha n k, ! C A>- G o r d o n , J . and R o i m ,' fit pophx -ectomm ,Mu; n \ , W J d la la < Ldc m England an . Rom.RT-.J Id, -\ hi; hi; and it. Roh- a. a (With 1 GI a))! m t . Tw oirr, C C an ! I d i 1 in Relation to the F ' 1 Figure m the T< \t Brp.Ni,:' F M Pat rot. Lhizm : Felix A Kr.tknPiw i T \ jde ad Badlb ( < Few ei and ot' Vi An Fe e i x . A and P i t i , R V B t'jjiho'H in Relat' Peatt. A E d he Vi ibdit A Method for tile R : N Cnderwood, E Ama (Moloney) Te.t W Figures in the Text) Orr, J ohn B oyd, T hom. Term Experiment >, Plate V I and 7 ( lru{ W hite, P B rite The Q the fdiolera Vibrio ight of, but tests indicate tected in the soluble ash. of chromium, ely consistent whole in es a partial disruption of 'i rates. ispersion in salt solution dude sweat and sebum, active chemically and '<le in the case of profuse ;cal character would be om a pathological case. chiefly as an aqueous 'y small extent, ion that the total solids e has a twofold aspect: of unsuitable material, uty subjects, and erection with external tion alone through the 5 has been known fre:ic symptoms, through >nnel as experimental so far to detect them id conditions, n perspiration, added vestigation. st ed. p. 69. d ed. pp. 405-6. ed. p. 798. -E d.) 207 MODERN VIEWS ON SILICOSIS1 B y W. E. COOKE, M.D., F.R.C.P., D.P.H. From the Pathological Dept. Wigan Infirmary (With Plates I-IV) I n tro du c tio n S ome months ago Prof. M. J. Stewart (1933) gave an address on silicosis in which he covered the whole of the pathology of the various types of the disease. It may seem strange, therefore, that the same subject should be chosen for discussion so shortly afterwards. My apologia is that silicosis presents many sided problems and that since Prof. Stewart's paper appeared the claim has been ventured that the cause of silicosis has been demonstrated. Discussions have been taking place during the past twelve months at the Institution of Mining and Metallurgy--discussions stimulating in themselves and showing the necessity of further research along old and new avenues. Therefore it may be useful to go over a few of the salient features common to all the group of industrial pneumonoconioses. In doing so, the obvious may sometimes appear to be stressed, but elementary principles are apt to be forgotten or neglected in discussions on etiology. Upder the general designation " Silicosis" are included the pneumono conioses of gold and other metalliferous miners, stone-masons, file-grinders, potters, etc., and the fibroses of coal-miners, haematite miners and asbestos workers. Whether the term is adequately or even approximately descriptive is a matter outside this discussion. " Silicosis" was defined by the International Congress on Silicosis in 1930 (1930) as a pathological condii.on of the lungs due to the inhalation of silicon dioxide (SiOjt), and to produce the disease, silica must reach the lungs in a chemically uncombined state. The definition was unequivocal and was acceptable to the two schools, one of which believed that chemical action was the more important and the other that the hardness, sharpness and insolubility of quartz particles caused the lung damage by mechanical action. In 1933 W. R. Jones (1933) exploded a mine beneath both schools. He stated that free silica (SiO,) played a very small part, if any at all, in the pro duction of silicosis. The villain of the piece, he claimed, was sericite--a hydrated silicate of aluminium and potassium. He based his opinion on the results of examination of the minerals obtained from lungs of many types of workers by 1 A paper read at the Liverpool Medical Institution on October 25, 1934. 208 Silicosis " sliming" with strong nitric acid. He states: (1) the bulk of the mineral residue obtained from silicotic lungs consists of sericite, which mineral is present in abundance in all the rocks and materials which give rise to dust in the working processes; (2) the number of quartz particles is very small com pared with the countless fibres of sericite; and (3) rocks which contain a rela tively small percentage of quartz, but which contain fibrous silicates such as sericite and sillimanite, give oS dust which has caused a large number of silicosis cases. He hastens to deny that minute particles of quartz could not, under any circumstances whatever, enter the lungs in sufficient numbers and cause silicosis, but insists that the fibrous silicates, sericite, sillimanite, and tremolite are of far greater importance than quartz, and, as regards free silica rocks, the cryptocrystalline forms, such as chert and flint, are more dangerous than the crystalline quartz. That sums up the various views on the subject to-day. The chemical theory has been mentioned, and while the solubilities of silica or the silicates in plasma have not yet been ascertained, there are certain known facts concerning silica that appear to have a bearing on the discussion. S o l u b i l i t y o f SiO, Silicon is, next to oxygen, the most abundant element in nature, and al though it does not occur free, its compounds, silica and silicates, make up 60 per cent, of the lithosphere. Silica is present in most river, well and spring waters, in some cases, as in the volcanic springs of Iceland, to the extent of 0-52 parts per 1000. Many petrifying springs owe their properties to solutioned silicic acid, and, of course, the silica of diatom valves and sponge spicules must be extracted from their environment. Mellor (1925), quoting S. Calderon, states the solubility of silica in distilled water to be 0-01 part per 100, increased in the presence of oxygen and CO,, nitric and sulphuric acids. The size of the grain has a remarkable effect on the solubility. Mellor (1913) gives the following interesting results. He took powdered rock crystal (quartz) and flint with a 15 per cent, solution of KOH and found: Avenge diameter of grain Rock cryetal dissolved % Flint dissolved % ... 165ft 0-06 2-32 32/t 6-40 12-10 And Lunge and Schoror-Tscherny (1894) found with a sample of powdered quartz the amount dissolved after two hours' action was: KOH solution % - NaOH solution % Quartz dissolved % 6-0 16-84 10-0 21-36 6-0 16-20 10-0 19-80 In thirty-two hours all was dissolved by a 15-0 per cent, solution of KOH, NaOH taking 2 hours longer. As mentioned above, but Tideswell (1934) reco from 3-0 to 6-0 per cent, silica. Lari We are dealing now particles obtained by in The numerous pape rs is the minuteness of the silica particles of a diatre between 1 and 8-5/t. On! exceeding 8-5/i, and th< repeated, and it must fce in lungs are of the order in diameter. When mineral residu numerable particles are light. There must be,then of silica in silicotic lungs. It has become usual tto 5/i in diameter and respirable. This is very n The minerals mention acids and are silica and contain, in addition, tho present a far different pn The average diamein 250/i (Miller, 1893) and ;! therefore, any anatomical They can and in fact do .-. are a marked feature in tl, asbestos workers, and ar normal adult lungs. The Lancashire coal sc. clarain, durain and fusam. red amber in colour and < each other when occurrn. opaque and angular, is ea~ In digests of coal-mini of coal are present in large of the spicules varies from The spicules are some , in the figures, which I beli Joum. of Hyg. xxxv ) the bulk of the mineral sericite, which mineral is s which give rise to dust in articles is very small cornrocks which contain a relaim fibrous silicates such as caused a large number of lartz could not, under any icient numbers and cause *, sillimanite, and tremolite egards free silica rocks, the j more dangerous than the o-aay. The chemical theory if silica or the silicates in ain known facts concerning ion. element in nature, and al ca and silicates, make up waters, in some cases, as in >-52 parts per 1000. Many oned silicic acid, and, of les must be extracted from lubility of silica in distilled sence of oxygen and CO,, a remarkable effect on the esuits. He took powdered lution of KOH and found : >65/i 96 52 32/i 6-40 1210 with a sample of powdered n was : NaOH solution % .--------*-------- > 50 10-0 16-20 19-80 per cent, solution of KOH, W. E. C o o k e 209 As mentioned above, the solubilities in plasma have not been worked out, but Tideswell (1934) records the extremely important observation that he found from 3-0 to 6-0 per cent, of the total silica in six silicotic lungs to be colloidal silica. L ar g e m in e r a l pa r tic les in lu ng s We are dealing now with the microscopical characters of the mineral particles obtained by tryptic digestion. The numerous papers on the mineral content of lungs stress one feature. It is the minuteness of the fragments. McCrae (1913) found 70 per cent, of the silica particles of a diameter less than 1p, and the remaining 30 per cent, varied between 1 and 8-5p. Only a negligibly small number of particles had diameters exceeding 8-5p, and the longest was 10-5 p. His observations have been repeated, and it must be accepted that the particles of silica and silicates found in lungs are of the order of 0-1-5 p, with occasional larger fragments 10-20p in diameter. When mineral residues are examined by dark ground illumination in numerable particles are seen which are invisible by transmitted or polarised light. There must be, therefore, enormous numbers of ultra-microscopic particles of silica in silicotic lungs. . . It has become usual to speak of " respirable" dust to indicate particles up to 5p in diameter and to discard particles over 10p or even 5p as non respirable. This is very misleading. Theminerals mentioned above are obtained bydigestion of lungs with strong acids and are silica and silicates. The deposits by tryptic digestion (1932) contain, in addition, those minerals which are soluble in strong acids, and present a far different picture. The average diameter of lung alveoli is given by different observers as 250p (Miller, 1893) and 300-500p (McDowell, 1933). There does not appear, therefore, any sn-.tomical reason why larger particles should not enter them. They can and in fact do so. Large fragments 20-100 or more micra in length are a marked feature in the trypsinised deposits of the lungs of coal-miners and asbestos workers, and are constantly present in fewer numbers, of course, in normal adult lungs. The Lancashire coal seams are composed of varying proportions of vitrain, clarain, durain and fusain. Of these, vitrain, clarain and durain are yellow to red amber in colour and doubly refractile, but cannot be differentiated from each other when occurring in small fragments in lung dust. Fusain, black, opaque and angular, is easily recognised. In digests of coal-miners' lungs particles of fusain and other constituents of coal are present in large numbers. PI. I, figs. 1-14 are examples. The length of the spicules varies from 22-5 to 85-Op. The spicules are sometimes covered with a golden yellow deposit as those in the figures, which I believe to be a colloidal combination of tissue proteins Joum. of Hyg. x x x r 14 I iiu S i h r o -o' *.i ii;'cirrn t oil ;r the m-oluble Ihe.-e i lies are four,'] i l'u,ou and :n 11ir o i a i r i in tic areas. PI II, figs 1 and 2. illustrate tbon in fibrosed areas, and also illustrate that the golden yellow material occurs i.n clumps without any apparent nucleus. The dust ui chrvsotile asbestos works--before tne days of exhaust ventila- , --consisted of asbestos fibres together with multitudes of black iror ' nntainmg fragments which appear as part of the fibre itself (II. II, kg- 3, I lies" particle^ were present m the lungs of the '.ori-mm m the dusts proce'-e- of manufacture. They are illustrated m PI. II, kg' 5 and 5. Fig. 4 shows the large black fragments in a tlbrotic area and Fig b a large particle 3G0p h-rigth in a m-crotic area of lung In trrptie digests of asbestos workers lungs tr.ire are, m aueLtio., a .imposed of a central core of abie-aoe gore co\"ie : v. H.t'gi vellow material as are are legion atid are now tarniliar to r\ . 1 i.e t \\ o iliu ' rat 'i ' P! 1, tigs. i0 arid IT, are examples of the hu,g, : - Ti.e upper one i- 13', ::i length and the lower ItH/i. ghe colloidal ina'ing of tan has been fract..r' ,.;:d shows the fine central adieWus hbre ba-e. Ik's f oa'mg soluble .a stro- acids and alkalis. PI. I. tig. It-, s' ows a fibre umbo- polarised light after th bodv had been treated with strong nitric acid. We know little about the gulden yellow mat< r.al. It wit '.stands prolong. trvps.msatioii and a considerable <l, gp-e uf in at e.uu e c u ' the Prussian he: 'eaetioi: for ion It no* ruref: ..agent t or ig" V irn give a c. a gs ccirntio'-ition from asbesto- lungs m a pure sum . Tb" bo : I. II. Bv-om, F.I.C . with th. following reui account for tLc fri> TLl- large P'.rr- : iron Qalt in enrs soiutioned. Bu* : v also gives 3.M into w haemoglobin Two conditionpro-, i.e-' of silma : ; r e - mce of p a : 1mo section alei . i, and I p t .. cases Large m;m mecham al d, t rt " K.p'a i 'Iulfti e?jl; hi Ferrous oxid Magnet win: o x /1> ('fkluua'. oxdde Alkalis . Nil 0 bO The chrvsofle m which woman worked contained 40 per cent, of com- ,od sdic... 41 con-, of mag:.' ium oxide and t! b per cent, of form .s Xv fre s.b a a- gres. r.t m ckiv-ogle nor m the mother rock associated wga ; .g 11 11f*' 1i sg.tO' theg c brv.-otile asbos'os is a' a-a 1 Lv \'ery W1 s '*. i l 1 - 1,.- e Min-'- A s m e tg . U.e I a h.refringeut, h a t -H a-Lmg to wh.eh ta h.r, , , l'W,- aaM^aW^aMAMn -Ca.. ja'V*:r'. >r>se bodies are found in . 1 and 2, illustrate them i yellow material occurs days of exhaust ventilaultitudes of black iron bre itself (PI. II, fig. 3). rs in the dusty processes and 5. Fig. 4 shows the a large particle 360 p. in ere are, in addition to urious bodies which are 'ith the same, or similar, oal-miners. Their shapes >. The two illustrated in . The upper one is 130/a f this has been fractured ating is soluble in strong polarised light after the It withstands prolonged . gives the Prussian blue radiogram give a clue to lings to obtain the bodies rained were analysed by % 67-80 32-20 /o 5-45 21-10 26-55 70-55 2-55 Nil 080 ed 40 per cent, of com2-8 per cent, of ferrous t,her rock associated with , attacked by very weak and calcium--and leave W. E. Co o k e 211 almost pure silica without destroying the appearance of the fibre. It is possible that some chemical action has taken place within the lungs which would account for the free silica in the analysis. The large percentage of iron in the ash is also remarkable. Possibly the iron salt in chrysotile is insoluble and remains after the Mg has been solutioned. But the golden yellow material of the bodies found in coal-miners also gives an intense Prussian blue reaction. The iron may be derived from haemoglobin. Two conditions seem necessary for the formation of the bodies, viz. the presence of silica or soluble silicates and spicules of insoluble mineral, and the presence of protein. But masses of the golden yellow material are present in lung section and digests without any discernible nucleus, as pointed out above. The bodies are not confined to asbestosis and silico-anthracosis, but are present in apparently normal lungs. Not very rarely both types are found in one lung digest. I have found them in general labourers, gas-workers, millhands, seamen, house-wives, dock labourers, haematite workers and fitters. The digests of these lungs all showed more silica particles than normal by polarised light. In addition, diatoms and fragments of Foraminifera may be encountered as well as unclassifiable particles (PL IV, figs. 4, 5, 6, 7, 8, 9, 10, and 11). An interesting fact may be recorded here. These bodies are consistently present in asbestosis, usually present in fewer or greater numbers in miners' lungs of the Lancashire coalfields and less frequent or absent in the silicoanthracosis of South Wales. In the silicosis of stone-masons, file-grinders, haematite-miners and Cornish tin-miners they are extremely rare, or absent. The reason, I think, is that long spicules of mineral are rarely present in these cases. Large mineral particles do then reach the alveoli. Whether they cause much mechanical mage when they are present in the nunbers found in coal miners may be debatable. The retention of coal dust in quantities sufficient to cause anthracosis seems to occur only in the presence of excessive amounts of silica (Cummins and Sladden, 1930; Cooke, 1932, 1932a). It is important to bear this in mind, because it has been suggested that sericite acts mechanically. Min e r a l s o b t a in e d b y n it r ic a c id d ig estio n As mentioned above the vitrain, clarain and durain constituents of coal are birfringent, but these are destroyed by the action of strong nitric acid and the ashing to which the lung residues are subjected. The remaining minerals are quartz, sericite, rutile, zircon, etc., but we are concerned only with quartz and sericite. As the birefringence of minerals is of great importance in the study of silicosis a word on the subject is necessary. Birefringence. If the visibility of a transparent particle is increased when 14-2 212 Silicosis the light has passed through crossed nicol prisms, the particle has two indices of refraction and possesses the property of birefringence. The greater the dif ference between the two indices (co ordinary index, e extraordinary index) the more is the visibility of the particle increased by polarised light. For example, the w index of quartz is 1-544 and the e index 1-553, the difference being 0-009, which is the measure of its birefringence. Quartz Sericite Canada balsam in xylene Canada balsam dried hard Gilson's euparal Refractive index 1-543 1-50- 1-65 1-524 1-54 1-483 Birefringence 0-009 0 042- 0-06 A good example of birefringence is seen in PI. I ll, figs. 1 and 2, illustrating one of the unclassifiable bodies found in lungs. It is 240/r long and embed ded in a mass of fibrous tissue in a coal-miner's lung. Fig. 1 was taken by transmitted light, and Fig. 2 between crossed nicols. The substance in the body is much more brilliant in Fig. 2, showing that it is doubly refractile. The above table shows that the birefringence of sericite is 4 to nearly 7 times that of quartz. To give maximum white polarisation a piece of quartz must be 4$ to 7 times the thickness of sericite of minimum size to give the same white polarisation. As the refractive index of Canada balsam is very nearly that of quartz thin flakes of that mineral may not be visible at all when mounted in this medium. Gilson's euparal has a much lower refractive index and is, I think, the best mounting medium for permanent specimens of lung sections and digests. Quartz particles are certainly more easily seen. Sericite. Secondary white mica or sericitic mica is hydrated silicate of aluminium and potassium (Kj3A10,6Si0j2Ha0 ) formed by the mineralogical transformation of potash felspar (KAlSi30,,). The name sericite is given when the white mica occurs in fine needles. PI. I ll, fig. 3 (photo taken between crossed nicols), represents a felspar crystal in granite undergoing transformation into sericite. The average diameter of these fibres is 20-8/u. When rock con taining these fine needles is drilled they are given off in clouds, and being extremely small and light remain in the atmosphere long after the heavier particles of the dust have settled. The section is of the granite near the lode in a tin mine in which silicosis is said to be fairly common. PI. I ll, fig. 4, represents a potash felspar crystal in which the secondary mica appears as flakes (average diameter 105p). The specimen is from granite near the lode in another tin mine a few miles away from the first. Silicosis is said to be rare in the workers in this mine. (The manager of the first mine told me he could tell the men who would get silicosis when they started work. They are of Spanish descent with bad tuberculous family histories.) These granites contain a large percentage of quartz. In Lancashire the mudstones and shales of the mines contain sericite in abundance. PL III, fig. 5, shows a section of a Lancashire shale (photo taken between crossed nicols) of sericite. PI. I ll, fig 0 ( return airway of a La nc drilling in shale was "ul a fragment of quart 2 . I light needles and flakes It is the custom n 1 mudstone. Sericite and qua.-!: 1 sericite fibre is very :-rr depth--0-5 cubic T! of PI. IV, fig. 1, is .-q and would contribute 1 fibres would be very n grain of quartz. Jones silica than sericite but t fibres of sericite in the action of sericite fibres quartz, is out of all p1 remembered, too, that 1 acid) from every siiico stone-masons, potte:s, Our results are q ir (1916) in 1916 were vr refractile particles seen at first surprising, bur t lung residues and a.ii repeated their work :n fig. 2, shows a section ot point out in their sectu microgr: n. The fir-t 1was the first to put jsL light.) The second, the third that in the ad vat the newly establishing 1 On examination b v . particles are quartz flak marked, the coverslip alcohol and dried; tne rest of the tissue. The s! drops of strong mtrx a repeated for three du'.> be seen that there are a appeared in the sec': u. particle has two indices ce. The greater the difxtraordinary index) the sed light. For example, : difference being 0-009, Birefringence 0-009 0-042-0-06 igs. 1 and 2, illustrating 240/i long and embed- Fig. 1 was taken by e substance in the body ubly retractile, oricite is 4} to nearly 7 -ation a piece of quartz m size to give the same arly that of quartz thin lounted in this medium, ud is, I think, the best g sections and digests. is hydrated silicate of ed by the mineralogical ,e 6ericite is given when ; (photo taken between lergoing transformation 20-8/1. When rock conff in clouds, and being long after the heavier granite near the lode in jn. in which the secondary pecimen is from granite om the first. Silicosis is ger of the first mine told ,hey started work. They stories.) These granites lines contain sericite in ,hire shale (photo taken W. E. Co o k e 213 between crossed nicols) revealing an enormous quantity of fine acicular fibres of sericite. PI. I l l , fig. 6 (photo taken between crossed nicols), shows dust in the return airway of a Lancashire mine, a hundred yards from the coal face where drilling in shale was taking place. It is almost all sericite with here and there a fragment of quartz. The heavier dust particles have fallen leaving the fine light needles and flakes in the atmosphere. It is the custom in many mines to dust the roads with crushed shale and mudstone. Sericite and quartz in the lungs. Jones points out that the volume of a sericite fibre is very small--2/x in length by 0-5 in width and the same in depth--0-5 cubic /x. The grain of quartz 10 x 10 x 10/x, outlined in the centre of PI. IV, fig. 1, is equal in volume to the 2000 sericite fibres around it, and would contribute more silica on analysis than 4000. The brilliant little fibres would be very much more striking by polarised light than the single grain of quartz. Jones argues from this that a lung may contain more free silica than sericite but not be affected so much by quartz as by the countless fibres of sericite in the alveoli. In other words, he states that the mechanical action of sericite fibres causes silicosis and that the amount of free silica, as quartz, is out of all proportion to the silicotic action it exerts. It will be remembered, too, that he stated that the bulk of the mineral residue (by nitric acid) from every silicotic lung he had examined, gold-miners, coal-miners, stone-masons, potters, etc., consisted of sericite. Our results are quite at variance with this. AVatkins-Pitchford and Moir (1916) in 1916 were very alive to the fact that the majority of the doubly refractile particles seen in lung sections of Rand silicosis were sericite. This was at first surprising, but the results of their experiments and examination of the lung residues and mine dust made the explanation apparent. We have repeated their work in Lancashire mine-drillers, stone-masons, etc. PI. IV, fig. 2, shows a section of a driller's lung, taken between crossed nicols. As they point out in their sections, there are three prominent features in this photo micrograph. The first is the birefringence of the fibrous tissue. (Moir in 1910 was the first to publish a photomicrograph of a lung section under polarised light.) The second, the great majority of particles seen are sericite, and the third that in the advanced fibrotic part few particles are apparent whilst in the newly establishing fibrosis they are very numerous. On examination by a higher power (PI. IV, fig. 3), it is seen that some of the particles are quartz flakes on edge. A fibrotic part of a section such as this is marked, the coverslip removed and the section passed through xylol and alcohol and dried; the part is ringed with paraffin wax after removal of the rest of the tissue. The slide is then placed level in an incubator, and two or three drops of strong nitric acid are placed on the selected portion. The process is repeated for three days and the slide allowed to dry. On examination, it will be seen that there are a hundred times more birefringent particles than at first appeared in the section, and the greater number of these are not sericite but maamA 214 Silicosis '.'..ir:.' \ \ atKir.'-I'itciifwrJ < and Ma r s CG.vlus.un.s were that the mineral l o n un t s of Rand silicotic lungs were identical, physically, chemically, and in the numerical ratios of the particles of quartz to that of particles of accessory polarising mineral, with the finer portions of Rand mine dust. Quartz particles "ere, of course, by far the most numerous. They add that there was no indication of physiological selection of particles except in regard to size. It would have been strange if there had been, and we have seen that even size is not very much matter--within wide limits. Our observations on the residues of lungs of several stone-masons, a file- grinder, a Cornish miner and a sand-blaster, lead to the conclusion that thev :.r. composed almost entirely of quartz, seriate fibres being comparative!'.rare, in the-f residue.., mounted in euparal, innumerable minute thin seal* - In Lancashire mini r- 1 1;cf. - 1 =. is a verv ram d.-ta-'- It is axiomatic that aork.'r-- in dnncultly solutd' ou.-t must base trace- of ' Oi r occupation im pended in tl.f.r lungs L \ ' d v underground v. order ha- a larger proportion of .-dica in his lungs than the normal 3 b per cent of lung ash. In this case the predominant silica compound is seriate, because it b pr- m the dust of the -bale- and mudstones of our coal measures and in the stone dust used in nianv mines to check explosions. The other components of none dust--fusam. ; train. tJarain and duram, micro-pore-, and uboia-sifiablo bodies and a fee. quartz grams--are also 1 resent, and a- an inr] yellow material of the curious bodies In tl 1'? It .e- obtained by nitric ac.J seriate is naturally predominant On *:.\n n. of the lungs of a put pon\ that laid been down the mim- for m <rt 1]; showed quantities of s e na t e fit ( s main::.- and u:*:;c ai ml (m there were no silicotic nodules ruT o;iier evidence of .-ihco-.s. The a! v. o!a r Sb in parts, showed a small amoun t of fibrosis, as did the pen- 1 .or. il ml jut the lungs were favour ably comparable with the lungs of an oidinary town dweller. Tryptic digests -boned the usual large numbers of coal particles with a few curious bodie- I be rinding? in the mme-rs' lung- are similar even when they have worked ten. ' venty. thirty or fifty sears underground, but there is no silicosis The storv is v. ry di be rent ^in the ca-t of th drillers. In addition to shale and mudstone-, s not ititic-querit amongst tbem. Thar lung- show either gross anthracotic consolidation cr the discrete nociular silicosis as it occurs in stone-masons and gold-miners. Sections urn: - polarised light arc- seen to be full of seriate, but the rutnc acid digests contain large quantities of minute flakes of quartz, far r x- .-eding :n numbers the neeales of seriate. Quartz particles, except whe " ' - r' a!;d quartz plates, unless the}' are seen edgewavs, are quite invisible 'I1 in lia met or, are extremely tbir, cigrs's ar*. examina; un' - r ic cat.:.et be scat. Th- sm-gestd secondary wb.te in occurs m flak, s am. at once by the exanever drilled m q . . whatever term be . silicosis is not pn se enough, especially . be advanced, their . cal composition of or mica plate"- doc.ii'jib- dust and m t Tiare are 5 .. : i- ngth of t;r;a rf , . dusty utm-a-ph-r- . existing d:- a-e, :- tat pat told To I pn 'idem. K< ttb. 1 i . dev. lop Bv ir.tr.r. ri:rr.ction of act...d ar.d Cummibg- w: sds a winch. !"-s r> the end tibro.-is d. net appear m c > g The u a - . u - of quartz is im p o ra: 3. The solubd.t have not been es;.: . been established \\ : the districts w1 4. A- b- t -, a s minerals. It may: 1v i , 11^^u' ! were that the mineral ally, chemically, and in of particles of accessory c dust. Quartz particles idd that there was no ot in regard to Bize. It ave seen that even size ral stone-masons, a file -lie conclusion that they es being comparatively rable minute thin scales nngent minerals. >e. It is axiomatic that of their occupation imts a larger proportion of ng ash. In this case the iresent in the dust of the >tone dust used in many of mine dust--fusain, ifiable bodies and a few silica action, the golden > obtained by nitric acid the lungs of a pit pony sections and nitric acid were no silicotic nodules u parts, showed a small it the lungs were favour . dwcilsr. Tryptic digests th a few curious bodies. n they have worked ten, ->no silicosis. The story is i to shale and mudstone, ->sandstone, and silicosis either gross anthracotic curs in stone-masons and to be full of sericite, but aute flakes of quartz, far ,z particles, except when .eways, are quite invisible iTe extremely thin--they . examined under perfect . The suggestion that the W. E. Co o k e ^ 215 secondary white mica in the shales and mudstones of the Lancashire coalfields occurs in flakes and not in needles, and is therefore not dangerous, is answered at once by the examination of the lungs and lung digests of miners who have never drilled in quartz rock. They contain numerous fibres of sericite, or whatever term be applied to the secondary white mica of the shales, but silicosis is not present. Even if the mica is said to be in flakes, these are small enough, especially after drilling, to enter the alveoli, and if a chemical theory be advanced, their action should be the same as the needles because the chemi cal composition of both is the same. Whether they are called sericite fibres or mica plates does not affect the issue. The same mineral is found both in the mine dust and in the miners' lungs. There are so many, hitherto unexplained, contributory factors in the production of silicosis--the concentration of silica and the size of the particle, length of time of exposure, the associated dusts, the energy expended in the dusty atmosphere, the presence of harmful gases, nasal obstruction and pre existing disease, and individual idiosyncrasy--that it is obvious the full storj is not yet told. To Prof. E. H. Kettle we owe a very great debt, and it would be fitting to mention a piece of work which throws considerable light upon the problem. Kettle (1934) has shown that colloidal silica injected subcutaneously causes an abscess with characteristic structure similar to the abscesses caused by amorphous and crystalline silica, although the latter take a little longer to develop. By intravascular injection of amorphous silica he produced the be ginnings of silicotic nodules in the liver, but these lesions retrogressed and disappeared entirely. The conclusion was that the amorphous silica was so soluble that it was removed before it had time to influence the tissues in the direction of actual fibrosis. In contrast to this he quotes the work of Gardner and Cummings who produced actual nodules by the injection of crystalline silica which, less readily soluble, can act persistently and long enough to cause the end fibrosis. Co n c lusio n s 1. Large particles enter the lung alveoli, and although sharp and angular do not appear to cause respiratory disability. 2. The consensus of opinion to-day is that the chemical action of free silica plays the major part in the production of silicosis. The size of the particles of quartz is important, probably on account of the effect of size on solubility. 3. The solubilities of the silicates, sericite and sillimanite, for example, have not been estimated, nor has their action in the production of silicosis been established. Wherever these silicates are found free silica is also present in the districts where silicosis occurs. 4. Asbestos, a silicate, causes pneumonoconiosis, but is unique amongst minerals. It may act as a soluble Bilicate or, after the bases have been dissolved by the tissue fluids and eliminated, the resulting free silica fibre may be the true cause of the fibrosis. 216 Silicosis it. One of the outstanding problems is to account for the reason why certain workers contract incapacitating silicosis, while some of their comrades doing the same work are not affected at all, and others, although affected to some extent, are not incapacitated. A cknow ledgments To the many friends--Profs. E. H. Kettle, M. J. Stewart, S. Lyle Cummins and T. B. Davie, Drs C. L. Sutherland and J. S. Pooley, Mr J. R. Lomax and Miss L. Lomax of the Lancashire Coal Research Institution, and Mr E. H. Dawson of the Camborne School of Mines--who have provided material and helpful criticism and to Mr C. F. Hill for his invaluable help with the photo micrographs, I wish to tender my most grateful thanks. REFERENCES Cooke, W. E. (1932). Brit. Med. J. i, 656. ----- (1932a). " SUico-Anthracosis"--Practitioner, 129, 483. ----- (1933). Mineral M atter in Lungs, Brit. Med. J . ii, 492. CraMXNS, S. L. and Sladden, A. F. (1930). J. Path, and Bad. 33, 1123. J ones, W. R. (1933). J. Hygiene, 33, 307-29. K ettle, E. H. (1934). The Action of Harmful D usts--Bull. Inst. Mining and Metall. 137. L unoe, G. and Schoror-Tscherny, M. (1894). Z . angeic. Chem. 7, 485. McCrae, J. (1913). Publication-s of the South African Institute of Medical Research, 1, 122 McDowell, R. J. S. (1933). Halliburton s Physiology, London, 232. Mellor, J. W. (1913). Treatise on Quantitative Inorganic Analysis, London, 664. ----- (1925). Treatise on Inorganic and Theoretical Chemistry, London, 277. Miller, W. S. (1893). J. of Morphol. 8, 165. Ross, J. G. (1931). C'hrysotile Asbestos in Canada, Acland, Ottawa, 18. " Silicosis"'-- Records of the International Conference at Johannesburg, 1930, 86. Stewart, M. J. (1933). Liverpool Med.-Chir, J. 41, 142. Tidesw ell, V. F. (1934). Refractories J. 186. W atkins-Pitchford, W. and Mom, J. (1916). Publ. S. African Inst. Med Research, 1913 21, and many other works. E X P L A N A T IO N OF P L A T E S 1-1V All figures reproduced from photom icrographs. The magnifications are given in diameters. N.B. The black cardboards on which the original figures for Plates II-IV came to us were 23 cm. long and in the reproductions had to be reduced to a length of 20 cm. so as to fit our page. Consequently allowance m ust be made for a slight error in the magnifications given in the explanations to P lates II-IV . (E d .) PLATE I Figs. 1-15. Bodies found in coal-miners' lungs. The measurements (in micra) of the spicules of fusain forming the core are: 1, 85-0; 2, 27-5; 3, 35-0; 4, 35-0; 5, 22 5; 6, 17*5 x 12-5; 7, 35-0; 8, 42 5 ; 9, 30-0; 10, 50 0; 11, the longest spicule in th e group is 77*5; 1 2 , 37*5; 13, 44-0; 14, 37*5; 1 5, a curious body from a case of asbestosis; a form unusual in asbeatoeis; length of core 40*0. x 400. (Reproduced by kind perm iss.on of the E d ito r of The Practitioner.) Figs. 16, 17. Two asbestos t<bodies attain . The col o. asbestos fibre bare. t 1 Fig 18. The central asbes; ; has been dissolved off t Figs. 1 and 2. Illustrating \ golden yellow materia visible nucleus at A > Fig. 3 Chrysotile as best i carding rooms conta1 ' . Fig 4. S hous these black Fig. 5. Large black fragm** - Fig 1. Unclassifiable be : ' x 500. Fig. 2. The same body p> j birefringence. Fig. 3. Photographed be-*< logical transforraati )average diam eter ol : h x 80. The slice was taken from ,i infrequent 1) , suffer in r bad tuberculous fam \ Fig 4. Photographed bet u clare felspar in the gr^r . mentioned above, 1 " particles is 320^, n.s.c x 80. Fig. o. Photographed b e t w mine. The shale contsi needles of se n a te . n 1 Fig 6 Photographed bt ' from the coal face * L heavier particles of ' ' floating in the atm esj t Fig. 1. (Diagram.) The .-a Around it the 2000 s hc i refractive index of t h 1* : very prom inent m set t Fig 2. Photographed b< t .r drills and work in she. described in the text , Fig. 3. H igh-pouer view : in addition to sencit- nt for the reason why some of their comrades rs, although affected to wart, S. Lyle Cummins y, Mr J. R. Lomax and -titution, and Mr E. H. provided material and le help with the photoks. 3 3 , 1123. M ining and M etall. 137. h. 7 , 485. o f M edical Research, 1 , 122. 232. sis, London, 664. m don, 277. iaw a, 18. burg, 1930, 86. 1 1nst. M ed. Research, 1913-- 1-IV II-IV came to ns were 23 cm. f 20 cm. so as to fit our page, c magnifications given in the ' (in miera) of the spicules of i, 22-6; 6 , 17'5 x 12-5; 7 , 35-0; ) is 77-5; 1 2 , 37-6; 1 3 , 44-0; "usual in asbestoeis; length of tor of The Practitioner.) W. E. Cooke 217 PLATE I (continued) Figs. 16, 17. Two asbestos bodies. 1 6 , 130/t long; 1 7 , 120/i long. Illustrating the large size these bodies attain. The colloidal coating of the latter has been fractured leaving part of the fine asbestos fibre bare, x 400. Fig. 18. The oentral '-''beatos core o f an asbestos body taken under polarised light. The covering has been dissolved off by strong nitric acid. The core is probably pure SiO ,. x400. PLATE II Figs. 1 and 2. Illustrating particles o f fusain in fibrosed areas o f a coal-miner s lung, and the golden yellow material not only covering some of the spicules, but also lying free without any visible nucleus at A , x 500. Fig. 3. (Jhrysotile asbestos fibre showing black particles within fibre, x 150. The dust in the carding rooms contained these black fragments in enormous numbers. Fig. 4. Shows these black particles in a fibrosed area o f an asbestos worker's lung, x 400. Fig. 5, Large black fragment of asbestos fibre in a necrotic area. The fragment is 360/i long, x 150. PLATE III Fig. 1. Unclassifiable body found in a coal-miner'B lung, 240/i long, taken by transmitted light, x 500. Fig. 2. The same body photographed between crossed niois, x 500. This is a good example o f birefringence. Fig. 3. Photographed between crossed niois: an orthoclase felspar crystal undergoing minera- logical transformation into the acicular form of secondary white mica known as sericite. The average diameter of the fine needles in the figure is 20*8p. Maximum 2 3 minimum 16^*. x 80. The slice was taken from th* granite near the lode in a Cornish tin mine where the workers, not infrequently, suffer from silicosis. The majority of silicosis cases occur in this mine in men with bad tuberculous family histories and of Spanish descent. Fig. 4. Photographed between crossed niois: a very coarse flakey white mica enclosed in orthoclare felspar in the granite near the lode o f a Cornish tin mine a few miles away from the mine mentioned above, where silicosis is said to be very rare. The average diameter o f the mica particles is 320p, maximum 510p, minimum 76 p. No fine needles o f sericite are present. x80. Fig. 5. Photographed between crossed niois: section o f a shale above a coal seam in a Lancashire mine. The shale contains 20 per cent, o f combined silica, the greater part of which is in fine needles o f sericite. x SO. Compare this with Fig. 3. Fig. 6. Photographed between crossed niois: dust collected in the return airway 100 yards from the coal face where drilling in shale and sandstone was taking place. The larger and heavier particles of dust have fallen, leaving the lighter particles of sericite and quartz floating in the atmosphere, x 80. PLATE IV Fig. 1. (Diagram.) The centre block in the figure represents a quartz crystal o f 10 cubic m- Around it the 2000 short lines represent sericite fibres 2>t in length and in breadth. The refractive index of the brilliant little needles being so much greater than quartz makes them very prominent in sections and digests. ^ Fig. 2, Photographed between crossed wools: a mine-driller's lung. Such men use compressed air drills and work in shale, mudstone and free silica containing rock. The prominent features are described in the text (p. 213). x 80. Fig. 3. High-power view of the more fibrosed part seen in Fig. 2. A few quartz particles are seen in addition to sericite fibres, x 600. 218 Silicosis PLATE IV (continued) Fig. 4. Curious body sim ilar to an asbeatosis body. From the lung of a dock labourer. x500. Fig 5. Diatom from lung digest of a case of sihco-siderosis. x 600, Fig. 6. Curious body from lung digest of an able-seam an. x 500. Fig. 7. Curious body resem bling those found in silico-anthracosie From lung digest of a London housewife, aged 54 years, x 500. Fig. 8. D itto in a London housewife aged 60 years, x 500. Fig. 9. Body similar to asbeatosis bodies from lung digest of a dock labourer, x 500. Fig. 10. " S ilico-anthracotic" body from a London housewife aged 64 years, x 500. Fig 11. D iatom s from a cotton worker's lung digest, x 500. JOURNAL OF HYGIENE, > ) ( MS. received for publication 9. hi . 1935.-- Ed.) JOURNAL OF HYGIENE, VOL. XXXV, NO. 2 PLATE II JOURNAL OF HYGIENE, VO L XXXV. NO. 2 PLATE IV