PHENOMENA OF INFECTION. 93 



The laws of nearly all the States take cognizance of 

 the dangerous character of certain occupations by 

 specifying the safe-guards under which work of this 

 nature is to be done, and penalizing disobedience. 

 They further recognize that many occupations are not 

 in themselves so injurious to health as the unhygienic 

 condition of the surroundings, the crowded states of 

 the work-shops, and the long hours imposed. Sweat- 

 shops exhibit in the highest degree the evils just referred 

 to. 



The predisposing influence of an occupation may be 

 exerted locally upon some organ, as the lung, or upon 

 the body generally. Thus pulmonary tuberculosis is of 

 frequent occurrence in persons whose occupations are 

 carried on in an atmosphere of dust peculiar to their 

 trades, e.g., stone-cutters, file-grinders, cutlers, cut- 

 glass grinders, etc., a danger which can be diminished 

 by placing suction hoods above the field of work. 

 Not all dust, however, is equally harmful, a difference 

 demonstrated in the case of coal miners who, while 

 breathing in a dust-laden atmosphere day after day 

 for years, are not markedly predisposed to tuberculosis. 

 Another example of the predisposing influence of occu- 

 pation upon an organ is found in seamstresses, who, 

 on account of the attitude assumed while working, 

 are predisposed to ulcer of the stomach. 



Occupations which create a general predisposition 

 are those in which the worker is either subjected to the 



