Document byBvoE8wNJdQBz1p2RjrQ5Rj3

i ( >!,' . To:;:cily of Vinyl Chloride t3 L:;I.o:-r/.cry Animals E. MASTROMATTEO, M.D., A. M. FISHER, Pb.D., IL CHRISTIE, B.Sc., and II. DANZIGER, M.D. Division of Industrial Hygiene, Ontario Department of Health, Toronto, Ontario; Department of Physiological Hygiene,School of Hygiene, University of Toronto, Toronto, Ontario; and, Welland County General Hospital, WellandOntario Introduction scribed os very slight. Elimination from the body FIRST prepared in 1S33, vinyl chlbride has come into increased use in the last decade in was very rapid. These authors quoted the work of Schaumann* with experimental animals. Mice, rats and dogs were able to endure repeated nar fniraerctahonetdicperpxoprdoloupsceitoritonienhsaoozf naprdoalcoyufvtitenhyeel xmcphoolnsouorrimdeeearrraeensidwnsiet.sllThecocoorsnisckeidwnntirtehaytoioudntasmanoayfgesp.eavtAehncoclootogrdicitnaeglnevtpoiedreSncccehenatoumfinlnivnaenirr, known. As an Industrial material, however,has been regarded as of moderate toxicity. A Thresh* old limit Value of 500 ppm was established by would be narcotic to humans in a short time and 12 per cent would be dangerous. Vinyl chloride has been studied as a possible the American Conference of Governmental In anesthetic agent Oster and associates4 noted that dustrial Hygienists. No industrial fatalities associated with its use Incoordinate*! muscular activity of the extremi ties and cardiac arrythmiaa of a serious nature Lave previously been reported. It was therefore were observed in all six dogs used in their experi of special interest when two fatalities occurred in a plant handling vinyl chloride. This plant is en gaged in the polymerisation of the gaseous mono mer with the aid of catalysts. One worker died while cleaning out a polymerization vessel and the other while working in a pit. Details of these two fatalities have been reported by one of the au ment. Carr and others* found that vinyl chloride produced sensitization of the myocardium in three of seven dogs in which it was administered as an anesthetic agent. Two eases of vinyl chloride gassing occurred in a factory in Great Britain where polyvinyl chlor ide resin was being made. These were reported by thors.1 Published information on the acute toxicity of vinyl chloride to experimental animals proved the Chief Inspector of Factories.* In one case a process worker was standing outside a polymeri zation vessel and washing it with a water stream. scanty. Patty, Yant and Waite* in 1030 reported on the acute response of. guinea pigs to vinyl After ten minutes of this he suddenly collapsed across the open manhole. Artificial resuscitation chloride. They found that exposure to 20 to 40 per cent In air killed guinea pigs in a short time; exposure to ten per cent was endured for several hours. Congestion and edema of the lungs with hyperemia of the liver and kidneys were noted. Peoples and Leake1 found the minimal anes thetic range of vinyl chloride in mice exposed for tea minutes was & to 12 per cent in air; 25 to 30 per cent was fatal in ten minute's. Dogs and rab bits were anesthetized within one minute when was successfully applied. Subsequent symptoms experienced by this worker were tightness of the chest, nausea, abdominal pain and headache. The second case occurred in a maintenance worker who was overcome whilo repairing a vinyl chloride leak. Both men wore hospitalized. Another worker whose hands were accidentally sprayed with vinyl chloride liquid under pressure developed a burn. Tills latter case was reported by Harris.* exposed to a concentration of about IS per cent in air. Recovery wus very* rapid with no apparent Such burns may occur with other highly volatile materials when sprayed onto the hmuls tin a liquid untoward effect men after prolonged anesthesia. under pressure. Lehmann and Flury4 noted that vinyl chloride Filatova and Cirmudierf'1* in 1957 reported on was highly imirotic hut had a wide margin Ixv hygienic conditions in a jmlyvinyl processing tween its narcotic and lethal conmitrations. Its plant in the U.S.S.II. The plant was engnged in local irritating clTci-t mid its toxicity were de tlm iKilyiiwrisatioH of vinyl chloride by means of m. A/htA \ 2/ (s) 3?r AP00013I25 /m/urtnal Ilyjicna Journal 393 a catalyst. Air sampling was done and the con- tions of vinyl chloride concentrations were done .vntmiicn nf vinyl cliluriilt! was found to vary in the test ohnmlxT during the experiments. Jn>m nltfiut 'JO pptn to 31'> ppm. (U.S.S.R. Experimental Procedures: Different groups of TluvsIwUI Limit. Value: 1 uig/Jiter or about 400 five mice, five mts and five guinea pigs were ppm). A spastic t\t>c Mtvxl vessel disorder was placed in the chamlx-r and exposed for thirty ilcM'rilx'd in workers from tins plant. minutes to concentrations of 10, 20 and 30 per liccsui.'C of the recent fatalities mentioned cent vinyl chloride in air. Similar groups of con above it was decided to undertake acute inhala trol animals were maintained but not exposed to tion studios in laboratory animals with commer- ' vinyl chloride, At the end of thirty minutes ex rially m ailable vinyl chloride. This was done both posure the test animals were immediately re for comparison with earlier work and to provide moved to fresh air. An additional group of five mfunimtion on the acute response and pathologi guinea pigs was exposed to a concentration of 40 cal change* in more than one species of laboratory per cent vinyl chloride in air. In all 65 experimen animal. tal animals were involved. Observations were re corded on the animals during and after exposure. Experimental Materials and Procedures Vinyl Chloride: The vinyl chloride was supplied in a metal cylinder under pressure. A commercial grade with the following specifications was used: The animals which died cither during the ex posure or after a delay period were autopsied soon after death. Two weeks after the exposure sur viving test animals and controls were sacrificed by a blow to the head with the exception of four Sp*dB *r*rltjr m S0*C tVt#r wbMI Boitia* r*a*t *C Kyd**ca ahlarida wnUo* Aertylaea Aeatoldabyda trea Purity (pa* cnat) Impuritlta (pat eaal) o.ao-e.Nt Kona -u to -as Nona IQ ppm muiBga M ppm rouimatt Eaaastialiy Uoa fra* MJ maximum QJ maximum control rats which were killed by exsanguination. All animals were examined for gross pathologi cal changes. Tissues were removed from all ani mals for microscopic examination. The lungs, liver, kidney and heart were removed m all cases. The brain, adrenal, spleen, trachea, lymph nodes, and the eyre were removed from represen tative animals in each group for study. The tissues were preserved in formalin and sections mode for Pure vinyl chloride is a colorless gas at room staining with hematoxyiu-eosin. Special stains temperature; its boiling point is -13.9*C. tt has were mode where indicated. a sweetish odor. Its flash point is given at --78*C and its explosive limits in air from 4 to 22 per Observations ceut. It has the molecular formula CHjtCHCL AniMal*.' Alice, rats and guinea pigs were used in the study. Test and control animals were taken from the same laboratory stock. All were fed a standard commercial diet and housed in the same way. All were of the same stage of development. Control Animal*: No symptoms were exhibited by the 16 control animals and no deaths occurred. Ten Per Cent Vinyl Chloride: The response of animals exposed to this concentration is recorded below In summary form; Equipment: The inhalation chamber capacity was 30.6 liters. It was equipped with a viewing ExpoaunTtnu (alia*to) iHfCMI window and an inlet tube- Vinyl chloride was re 1 8U*bt irritation la tnfe* nod nm. leased in gaseous form through an adjustable valve on the top of die containing cylinder, then through connecting rubber tubing and a recali brated Fisher Sow-meter. Fresh air was pumped by motor at an adjustable controlled rate through S himnaad motor activity Sm la miaa. than rtta tad fuJaan pica 10 Incnaatd motor activity la dl rpadta; twitching t axmmiUe* ta mica, U PrewuMad utmor, taacteady (tit and muMulu intoordiction in D ipartm a meter. The streams of air and vinyl chloride were combined at appropriate rates of flow by a glass Y-tube lending through further rubber tub SC JUimrafld rat* in aide pmrtioatmiaeulai' incoordination, tmroora and twitabiat el extmniUca la cuisan pica, IS ilia nod rata uaeenacioia, pjiut pip ing to the animal chamber inlet, to deliver a rnntimiiitR stream in the desired proportions. Calculation* :iwl adjustments were made to pro duce the billowing flow concentrations of vinyl very us*tend? but atiK ataodia*. SO Mtae nod rata in dotp nareoai*; cuImo pip innkU position with tftmem-rea* unenaaefoua. chloride in air for delivery: 10, 20, 30 and 40 per Exposure was stopixxl and the animals removed cent. All loncnitrutums are expressed in this re to fresh air. All recovered within five minutes. port as |r cent by volume in air. Xo determina Tiecnljf Per Cent Vinyl Chloride: The response APOOd 13126 i Industrial Hygiene Journal 395 :i catalyst. Air dimpling wjis done find the con- tions of vinyl chloride concentrations wero dona crntratk'ii i>{ vinyl i-iilnri*l w:l> found tn vary in the test i.-hiimix-r diirinc the experiments. j'roni ultout 20 ppm t>> filxiut dl.') ppm. (U.S.S.Ii, Experimented Proecdurct: Different groups of Tlm^lioid Limit Value: 1 mg,/liter or al)OUt 400 five mice, five ruts ami five guinea pigs were ppm). A ppu*lU- tyj blryxl vessel disorder was placed in tlie chamber and exported for thirty /loeriixv! in v\nrki'rs from this plant. minutes to concentrations of 10, 20 and 30 per lk'rtui/.e of the recent fatalities mentioned cent vinyl chloride in air. Similar groups of con above it ivas decided to undertake acute inhala trol animals were maintained but not exposed to tion (.tudies in laboratory animals with commcr- ' vinyl chloride. At the end of thirty minutes ex- ciully available vinyl chloride. Tliis was done both )xuro the test animals wero immediately re for comparison with earlier nwfc and to provide moved to fresh air. An additional group of five information on the acute response and pathologi guinea pigs was exposed to a concentration of 40 cal changes in more than one species of laboratory per cent vinyl chloride in air. In all 65 experimen animal. tal animals were involved. Observations were re corded on the rmimrtls during and after exposure. Experimental Materials and Procedures The animals which died cither during the ex posure or after a delay period were autopsled soon Vinyl Chloride The vinyl chloride was supplied after death. Two weeks after the exposure sur in a metal cylinder under pressure. A commercial viving test animals and controls were sacrificed grade with the following specifications tvu used; by a blow to the head with the exception of four control rats which were killed by exsangumation. Sptdlo cmvttv l WO Wtsr eentout B4Ub rB| *C Hydrogen tbMd* must Aertylts* Assuldtbyds Iron Purity (pe t) Impurities (pat M*t) Non* -ills-94 Nm 10 ppn sauisiitjs M ppm dulmum EMautiillr ben In* tt.l maximum 0.1 maximum All animals were examined for gross pathologi cal changes. Tissues wero removed from *11 ani mals for microscopic examination. The lungs, liver, kidney and heart were removed in all cases. The brain, adrenal, spleen, trachea, lymph nodes, and the eye wero removed from represen tative animals in each group for study. The tissues were preserved in formalin end sections made for Pure vinyl chloride is a colorless gas at room staining with hematoxylin-eosiii. Special stains temperature; its boiling point is --13.SC. It has were made where indicated. a sweetish odor. Its flash point is given at --78C and its explosive limits in air from 4 to 22 per Observations ceut. It has the molecular formula CIIf;CHCL Animals: Mice, rats and guinea pigs were used in the study. Teat and control animals were taken from the same laboratory stock. All were fed a standard commercial diet and housed in the same way. All were of the same stage of development. Control Animals; No symptom* were exhibited by the 16 control animals and no deaths occurred. Ten Per Cent Vinyl Chloride; The response of animals exposed to this concentration is recorded below in summary form: Equipment; The inhalation chamber capacity was 56.6 liten. It was equipped with a viewing EiposunTtas (minute*) window and an inlet tube. Vinyl chloride was re leased in gaseous form through an adjustable valve on the top of the containing cylinder, then through connecting rubber tubing and a recali brated fisher flow-meter. Fresh air was pumped I Stitfat inflation is mis* xnd rats. S Inemaatd motor activity tort la mics. thw mt* ui (iilsu pit*. 10 InsNMsd motor activity la *U meats; twttchlur el vstmmitim la mW 11 PtOMuassd tremor, tateiJy fait ud by motor at an adjustable controlled rate through a meter. The streams of air and vinyl chloride were combined at appropriate rates of flow by a glass Y-tube leading through further rubber tub muscular Incoordination la Q spaticc. to Mis* and itU 1b tide position; muscular incoordination, trsmoc* and twitofciaf of extremities in mtinea pica. IS Mias xnd rata unconscious, fuieea alas ing to the nnimul chamber inlet, to deliver a continuing stream in the desired proportions. CaU-ulntimn* ami adjustments were made to pro duce the following flow concentrations of vinyl very unsteady but still rtsodia*. Miss and nits la deep aareosis; ftSasa pip Inside petition with trimixs S*S uBsockseioua. chloride in air for delivery* 10, 20, 30 and 40 per Exposure was stopped and the animals removed cent. All comTiitratwms an* expressed in this rc- to fresh air. All recovered within five minutes. jjort as jjcr cent by volume in air. No determina Twenty Per Cent Vinyl Cldoride; The response APOOOt3127 3M October, lO'JO of animal* e\|n-C'l to this concentration is re corded Ixjlu'v in summary form: Elpoiurr Tima (minutes) 1 3 S 10 ItM SI H Reapsnc irnUuon In mice and rate. Ms*fulur inroonJin.nion in met and nLi. Mjsaaad tutaon their tidp* with marked tnmera and twitching of the extremitiea; uutcadmtj and muieulxr ircoordination In guinea p><% Sl.ee and rati uneonieioui with rapid imtular brtmtlunt; jttiinea pt|i un-, aonxdoua hut thawin* marked twitch, in*. All animela iadecprercorle; reepirationa Irtefiilir and rapid. Daap naranaiai brratbia* aloar and shal low-. Bnatbia*eu*d in ana mouic; frothing at mouth and nnithii in mioa and Ate. All aoimala In deep oaraala. Exposure was stopped and the animals removed to fresh air. Mice and rats recovered faster than the guiriea pigs and appeared normal within five minute* except.for one mouse which was dead. The guinea pigs continued to show muscular in coordination, Unsteadiness on their feet until 20 minutes after removal from exposure, Thirty Per Cent Vinyl Chloride: The response of animaht exposed to this concentration is recorded below in summary form: ^ IGen itevtd irritation Immediately and Iha Sats ebowed Irritation quirkljr tlunafttr. I lloaetlkr Incoordination lit mica aid rata. I Mica aad rata in alda poaitloa with toarkrd (wson and twitehiu of tho aatramltlra; mvaeular Inewiinatio* ia (uiaaa pi** with devrlopin* patwlyla ol tha axtramitlri. I AS aaltnala uoeaMeiatws rapid imtular raapitatioaa la mice and rmta with frothin* about note and ciouthr twitchin* of astraniiira ttifl eceumd BaoaaiOMlIjr in fulnca plaa. 10 Rt*pirtiMaaUpt*diBinic:brrMhiiic lew and shallow in rnw; culms pica atill aihibltad ocraaioaal twitchin* mownaau of tha cstrwmlUn. 11 Rraathln* atppo<i la ratal rcapiratlona ilo* and ahaHow in ctiinaa pica; twitehin* af aatrCmitlra etlll prracot In suioca pica M Mica and rata still; auinc* pips in deep narcotic with slow ihallow brratlUac Exposure was *top|)cd and thr animals removed to frcuh air. Thr miw anti rats were deswl. Tho guinea pigs took 25 minutes to return to their normal ap|>c:trai-e and activity. Otte guinea tng from thin group died within 24 Innas following cx|tnsutv. Tasli; 1 Number of Death* in Different Group* of Five Mice, Rat* ami Guinea Pig* L'.\pn.*ed for Thirty Minute* lo Varying Concentration* of Vinyl Chloride in Air Vinyl chloride concentration 'per cent by volume in 4ir) Laboratory animal Mice RaU Guinea pig* Total 10 0/1 0/ C/S 0/1S 30 I/O / 0/1 I/ll 30 3/S I/S l/S* U/ 40 -- -- I/S* 1/1 Tout I/ll I/ll J/S 14/M A dalayaddaatli oeeunadwithinSf hours follow ioctepeaura. Forty Per Cent Vinyl Chloride: Only five guinea pigs were exposed to this concentration. Signs of irritation were immediately apparent. Muscular incoordination appeared within seconds. After five minutes all the guinea pigs were unconscious with slow shallow breathing. At the end of the exposure period one guinea pig was dead and the remaining four were in deep narcosis. These sur vivors took 30 minutes to return to their normal appearance and activity, but one died within the following 24 hour*. The number of deaths occurring in different groups of five laboratory animals exposed for thirty minutes to varying concentrations of vinyl chloride In air is shown in Table I. Pathological Findings Gross pathological and histological studies were carried out. The findings are summarized below. Control Animals: These animals showed no gross or microscopic evidence of damage. Ten Per Cent i'inj/f Chloride; All test animals survived this exposure. They were sacrificed two weeks Inter. On gross examination there was evi dence in mice of slight hyperemia of the lungs. Tlti* was less marked in rats. Guinea pigs showed no difference from control animals. On histologic examination the mice showed very slight engorge ment of the pulmonary vessels. Onfe mouse showed degenerative changes in the tubular epi thelium of the kidney with hydropic swelling. The rats showed slight congestion of the capillar ies In the lung. LungS in tlw* guinea pig were also slightly more hyjk'rcmic than those of the control animal*. Tietnly l*er Cent Vini/l Chlorirle: One mouse died tut n result of 30 minute* oN]u*ure to thi* concentration. Pulmonary congestion was evident on gross cxninhuitimi. Mirmsenpiritlly, then* was AP00013I28 f fh'tv'lriil Ilj-jUttC 307 tv.- U.h..| v ...!- in tl.* with ficed two iv,vk* after expirin'. There was a pttlchy >! ;iirl min.mil i'. tcudctii y for the lilmul to remain unrliittrd in the Tin- kitlm \ .!m\u*il ilcu-'urmtivc animals dying during exposure. This feature was i li;tnm-> in tin* i`pithfl:um <*f tli` i.nvoluti'd tu noted in the two human futilities mentioned ear bules. lier hut it is not u i>ecifie characteristic of vinyl Tin. tf-t iiriinuiU surviving this exposure were chloride. sarrilii-eti :u tun week*. Ou i:fo. examination, roniii-'tiou of tlif tunizK \vy pre-mt in nil "jiveics, Discussion hut it w:i mnri' marked in the mice and rata than in tin* pigs. Histtjlo^k'uily, there was evi- tlenre of imluiunary congestion in exposed ani mals. Sum* fatty infiltration was present in the liver of one ret. All other tissues studied appeared normal. Thirty Per Cent Vinyl Chloride: Gross examina tion of the animals which died as a result of this exiwsure revealed congestion of the lungs with hemorrhagic areas. The mice and ruts in addition showed congestion of the liver and kidney. The one guinea pig death was delayed. In this animal then* was marked congestion of the lungs with licmorrhages and the liver was distended and very friable. The microscopic changes in the animals which died included marked engorgement of the pulmonary blood vessels with edema and hemor- rhuges in the lungs. The trachea of one rat showed superficial desquamation of the epithelium. Con gestion was also evident in the liver and kidney *of the mice and rata. The liver of the guinea pig which had the delayed death showed severe fatty degeneration of the liver confirmed with frozen sections stained with Sudan III. The four surviving guinea pigs were sacrificed two weeks later. Marked pulmonary congestion was present with hemorrhagic areas and edema. In one case there was evidence of secondary bac terial infiltration. The Uver in these guinea pigs gave the appearance of fatty infiltration but no fat was demonstrated on frozen section. Forty Per Cent Vinyl Chloride: One of five guinea pigs exposed to this concentration died during the exposure and another died within 21 hours. The two which died showed marked con Tito ros|)onso of guinea pigs to inhalation of vinyl chloride was similar to that reported by Patty, Yant and Waite. The guinea pigs in our study, however, tolerated a greater exjxwurc dur ing the experimental period than either the mice or rats. The results in mire agreed elojely with those* reported by Peoples and Leake. Rata were similar to mire in their response. The pathological changes in animals which died as a result of exposure were mainly those of vascular engorgement of the lungs with hemor rhages and edema. The severity of these changes varied with the severity of exposure. In the higher concentrations, pulmonary change was marked with severe damage to the tracheal epithelium. Congestion of the liver and kidneys also occurred in test animals. These changes are similar to those reported by Patty and associates. Evidence of pulmonary congestion was still present in surviving animals sacrificed two weeks after exposure. Patty and associates reported that such changes had disappeared inabouteight days. Degenerative changes in the tubular epithelium of the kidney were noted in one mouse dying as a result of exposure and in one mouse sacrificed two weeks after bring exposed. Such changes, however, were minimal and not shown by other animals in the group. One of the guinea pigs with delayed death fol lowing exposure showed severe fatty infiltration of the liver. Changes suggestive of fatty infiltra tion were observed in other exposed animals but not confirmed by frosen sections stained with Sudan 111. gestion of the lungs with hemorrhages on gross examination. This wot-also evident on micro Summary scopic examination. Tbs Uver of one of these gave Separata groups of laboratory animals com the appearance of fatty infiltration, but no fat prising five mice, five mts and five guinea pigs vtiuld bo demonstrated on frozen section. were exposed in an inhalation chamber to concen The three surviving guinea.pigs were sacrificed trations of 10, 20 and 30 per rent vinyl chloride two weeks later. Marked congestion of the lungs in air for 30 minutaSi An additional five guinea with hemorrhage was evident on both the gross pigs were exposed to s 40 per cent concentration and microscopic examination. In one guinea pig, for n similar period of time. The rcKponso by each tin* tracheal epithelium was complctuiy-ubscnt. of the three sgxxios to them1 ronreutmtions is Pathological studies Which were made of the noted. brain, heart, spleen, adrenals, lymph node* and Initiation of theso relatively high concentra the eyes showed no difference between controls tions produced narcosis and death. Mire were the and imimals dying ns a result of exposure or be most Hiisreptihla with guinea pigs coimidcrubly tween control* ami the surviving animals sacri ' more resistant. Rats were similar to mice in their AP00013129 SS3 October, 1S60 response. Exposure to ten ]>cr cent vinyl chloride in e,ir produced deep narcosis in mice and rats but no deaths; 30 per cent concentrations killed mice and rats, Exposure of guinea pigs to 20 per cent produced deep narcosis; but three of five guinea pigs survived exposure to 40 per cent con centration. Animals dying as a result of exposure were autopsied shortly after death. Survivors and con* trol animals were sacrificed two weeks later. Cross pathological and microscopic studies were done and these findings are described. The principal pathological changes in animals dying from exposure were congestion of the lungs with pulmonary edem* and hemorrhages in some, and congestion of the liver and kidneys. Failure of the blood to clot was also observed. One of the three guinea pigs which died following exposure showed severe fatty infiltration of the liver. Survivors sacrificed two weeks after exposure showed little difference from the control animals. Pulmonary congestion was still evident but liver and kidney congestion was not. References 1. Daxsih, H.t Accidental Potanins by Vinyl Chloride: R*. port of Tro Cimi, CtnadiAn Ut4. Ximc. /. <1.- S2S (April IMO). 1 2. Patty. F. A.. W. P. Y*, ax* C. P. Waits: Acute Rmpobm of Gulwa Pic* to Vapon of Bern* N Cemmorelnl Or-mU CampauedA V. Vloyl CUoriC*. J*. Staid fftpL tit 1M3 (AU|uM 1932). | J. Fiona, A S-.amoC. D. LiAxiiTh* AaathoiicAetfeaot Vinyl CWorld*. J. piuarmtetUn It- ill (1633). 4. LiHVAxir, K. B., 4 F. FlCHY: 7*i*tar oni JFfrwitr / JiUMrioi StlHaU, TmulAUd bjrE. iii H. 7, Smith, Jr., William* 4 Wilkin*, BaltlnOM (IMS). 1 SeKATXAXX, O.sCiudby Ltbmnio, X. B. udF. Flwrr. fl. Oam, R. Hi C. J. Cam, J. C, Kiaxt*. amo tf. f, Savu- waio: ABMttai* XXVH. Kimh viU Vinyl CUorida. AntMkutokn <' US (tUTt. 1. Cam, J-, R. K. Bommox, J. F. Vitcka. ah J. C. Kumt /a.: 4uriM* XXIV. CtolWal Co--titwtloa el Hydra* cnrfeo-- Mi Cuilaa Auiomatirity, J. Plam. and Srptr. nmp. tTi I USff). a A*nol Hepart of d* Ctaf f--ptawsfAri#*<Mjlrdo Ita* Ml, London : H.M.S.O, Cad. m (Hunk 19M). I, Hawu, D. K.: HWth ProbUn* in th* Msaultetui* ui Vm<H Plaatim, Brit. J. Ini. tltd. /0.'21SG9U). ia Fuatoya, V. S., axb E. B. OBoniaaa: Byttate Workto* Conditio-- to Potyrioji CUeriia Tar PImW. Otrirao pp. S*-4 (JanuaiT 1917). Ahetmnad to Atof. / WarW Mad. fir WtfulrlMT). 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