322 RESPIRATION 



consideration. To this subject I have given very close attention 

 in recent years, and a full general discussion of it will be found in 

 the recent Report of the Committee on Control of Temperature 

 in Mines. 14 



Owing to the nature of their work and the dry conditions in 

 deep and well-ventilated mines, miners are very much exposed 

 to dust inhalation; and the prevalence of "miners' phthisis" 

 among certain classes of miners led me to the investigation of the 

 effects of dust inhalation. Both men and animals are in general 

 more or less exposed to dust inhalation. The problem presented 

 by dust inhalation in mining and other dusty occupations is thus 

 only a part of a general physiological problem as to how the dust 

 inhaled along with air is dealt with by the body. It is evident that 

 if the insoluble dust which is constantly being inhaled by civilized 

 men, particularly in towns and in dusty occupations, accumulated 

 in the lung alveoli, the effects would in time be disastrous. There 

 is, however, no evidence that such effects are ordinarily produced. 

 The lungs of a town dweller, for instance, are more or less black- 

 ened by smoke particles, but remain perfectly healthy; and the 

 same applies to the lungs of coal miners and of persons engaged 

 in many other very dusty occupations. In other cases, however, 

 such as certain kinds of metalliferous mining, steel grinding, 

 pottery work, etc., the effects of continuous inhalation of the dust 

 are disastrous. Why have certain kinds of insoluble dust no cumu- 

 lative bad effect on the lungs? Why, on the other hand, have other 

 kinds such disastrous cumulative effects? When the first question 

 is answered the second becomes relatively easy. 



It is in the production of phthisis (pulmonary tuberculosis) 

 that the continued inhalation of a dangerous variety of dust shows 

 its effects most clearly. The following table, which I compiled 

 from the statistics of the Registrar General for England and 

 Wales, shows the marked contrast between different occupations 

 as regards the effects of dust inhalation in producing phthisis. 

 Two dusty occupations are included coal mining and tin mining. 

 Of the two, coal mining is much the dustier occupation. It will be 

 seen, however, that among coal miners there is not only very little 

 phthisis, but even less than among farm workers, and much less 

 than the average for all other occupations. Among tin miners, on 

 the other hand, there is a great excess of phthisis; and detailed 



14 First Report of the Committee on Control of Underground Temperature, 

 Trans. Inst. of Mining Engineers, 1920. 



