THE miners' phthisis OF THE RAND. I29 



fluence of silex dust has been obtained amongst the flint-knappers 

 of Brandon, by Dr. E. L. ColHs, H.M. Inspector of Factories. 

 When the surface of a flint is flaked ofif by a blow a fine smoke 

 of siliceous dust arises, and the worker who is exposed to the 

 repeated inhalation of such dust is unusually liable to develop 

 the form of phthisis known as knappers' rot. Flint-knapping, as 

 Dr. Collis remarks, is probably the oldest of the world's indus- 

 tries; it is an interesting speculation as to the extent to which 

 our troglodyte ancestors suffered from silicotic phthisis. 



True miners' phthisis is found in Great Britain among the 

 tin miners of Cornwall and the ganister miners of Yorkshire and 

 elsewhere. It is. however, very encouraging to find that the 

 mortalit}' from this cause amongst ganister miners has now 

 almost disappeared, owing to the enforcement of common-sense 

 precautions. 



Ganister is an extremely hard sandstone, containing from 

 97 to 98 per cent, of silica. It is ground to powder, mixed with 

 lime water, and compressed into fire-bricks for lining steel con- 

 verter-furnaces. 



The gold-bearing reefs of the Rand are a conglomerate of 

 fjuartz pebbles in a siliceous matrix, and this conglomerate lies, 

 for the most part, embedded in extensive deposits of quartzite. 

 The gold-bearing conglomerate contains about 86 per cent, of 

 silica, whilst the quartzite, which has to be tunnelled through 

 to reach and expose the reef, contains an even higher proportion 

 It is the drilling and blasting of such deposits which gives rise 

 to the dangerous siliceous dust. 



A description of the clinical features of gold-miners' 

 phthisis is unnecessary here ; from the physiologist's stand- 

 point, however, it is of interest to note that the outstanding 

 feature of the disease is a progressive loss of the normal elas- 

 ticity of the lung. The normal lung, being elastic, is capable 

 of following the movements of expansion and contraction of the 

 chest walls. The lung of the silicotic patient, on the other 

 hand, is increasingly resistant to inflation by the current of in- 

 spired air, and the ultimate result is that as the lung cannot 

 follow the chest wall when this expands, the chest wall becomes 

 more and more fixed in the position of expiration. The most 

 forcible inspiratory efforts eventually fail to elevate the chest 

 wall against the pressure of the atmosphere. 



A striking and apparently consistent peculiarity of the sili- 

 cotic lung, as found on the Rand, is the deposit in it of ex- 

 traneous pigment in conjunction with the extraneous silica ; the 

 result of this peculiarity is that the degree to which silicosis has 

 advanced can be roughly estimated by the extent and character 

 of the deposits of pigment in it. The normal lung has but very 

 little extraneous pigment in it ; in the early stages of silicosis we 

 find very numerous, small, discrete islands of pigmentation ; in 

 the middle stages these islands have become so numerous that 

 many of them coalesce with their neighbours, and thus give rise 



B 



