Document ppn2dMLBNkp3Vrvv8OQgyJGgX

I Now, the next Important thing is to insure that you get all tne population you're after. Here is, just to emphasize this point, the prevalence of disease according to our categories, 0, 1, 2, 3> simple pneumoconiosis, mass ive fibrosis, to a hundred consecutive cases attending the certifying panel at Collier. You see the first two are net f represented, miners and ex-miners admitted to our ward, high proportion have exited; ex-rainers in a town, this dis tribution; surface workers, and the designed underground population, and you will see that these three all agree fairly well, but the certified cases and the hospital cases show a gross distortion of the distribution of disease, although all these cases come from the same geographical area. These are the collierys we have studied which have been in South Wales. Some of the collierys already have been studied by the Medical Research Council in 1938. Ve have re-read the films in our classification and used their- figures. We have also, particularly carefully, stud ied some steam coal mines, this group here in South Vales. Steam coal is our semi-bituminous, -and an anthracite sdne with very little disease in it. This is another steam coal mine, and two mines in England with rather low concentra tions of dust, two mines in England in Lancashire and Cum berland with very high dust concentrations reputedly, from SEVENTH SARANAC -0249