AND PREVENTION OF PHTHISIS. 405 



taken possession of some minds, others ignore almost 

 completely the possibility of infection. The fact that 

 investigations have been published of late, with the 

 object of discovering tubercle bacilli in the breath, 

 sufficiently indicates that the conclusive researches of 

 earlier investigators have not received the proper 

 amount of attention. 



6 We must regard it,' says Cornet, * as firmly esta- 

 blished that, under no circumstance, can the bacteria 

 contained in a liquid, or strewn upon a wet surface, es- 

 cape by evaporation or be carried away by currents of 

 air. By an irrefragable series of experiments Nageli 

 has placed this beyond doubt.' 



The evidence that the sputum is the real source of 

 tuberculous infection is conclusive ; and here Cornet 

 earnestly directs attention to the fact that in the houses 

 of the poor the patient commonly spits upon the floor, 

 where the sputum dries and is rubbed into infectious 

 dust by the feet of persons passing over it. The danger 

 becomes greatest when the dry floor is swept by brush 

 or broom. There is a still graver danger connected with 

 the habits of well-to-do people who occupy clean and 

 salubrious houses. This is the common practice of 

 spitting into pocket-handkerchiefs. Here the sputum 

 is soon dried by the warmth of the pocket, the subse- 

 quent use of the handkerchief causing it to be rubbed 

 into virulent dust. This constitutes a danger of the 

 highest consequence, both to the individual using the 

 handkerchief and to persons in his immediate neigh- 

 bourhood. 



It is a primary doctrine with both Koch and Cornet 

 that tuberculosis arises from infection by the tubercle 

 bacillus. Predisposition, or hereditary tendency, as a 

 cause of phthisis, is rejected by both of them. Facts, 

 however, are not wanting which suggest the notion of 



