188 



Dr. A. Ran some. On certain Media for 



The conclusions drawn from the experiments recorded in this paper 

 were : — 



(1) That finely divided tuberculous matter, such as pure cultures 

 of the bacillus, or tuberculous matter derived from sputum, in day- 

 light and in free currents of air is rapidly deprived of virulence ; 



(2) That even in the dark, although the action is retarded, fresh 

 air has still some disinfecting influence ; and 



(3) That in the absence of air, or in confined air, the bacillus 

 retains its power for long periods of time. 



These observations afforded an explanation of the immunity of 

 certain places, and the danger of infection in others. They show 

 that where tuberculous sputum is exposed to sufficient light and air, 

 to deprive it of virulence before it can be dried up and powdered into 

 dust, no danger of infection need be dreaded. It would appear further, 

 from this research and others, that it is only when there is sufficient 

 organic material in the air, derived from impure ground air, or from 

 the reek of human bodies, that the tubercle bacillus can retain its 

 existence and its virulent power. Long-lived though it may be under 

 these latter conditions, it is rapidly disinfected by the natural agencies 

 of fresh air and sunlight ; so rapidly that, when these agents are 

 present, even in comparatively moderate degree, the tuberculous 

 material cannot reach its dangerous state of dust before it is deprived 

 of all power of doing barm. 



But, in addition to the above-mentioned researches, it seemed 

 desirable that an attempt should be made to ascertain what part was 

 played respectively by the several forms of organic impurity that are 

 present in insanitary dwellings. Hitherto, so far as I know, no 

 attempt has been made, in the laboratory or elsewhere, to imitate the 

 actual conditions that prevail in snch houses. It was determined, 

 therefore, to collect the aqueous vapours arising from the ground or 

 from human bodies, and to submit these products to the test of trying 

 whether they would serve as cultivating media for the bacillus of 

 tubercle. 



Many years ago in a research, the particulars of which are given in 

 an appendix to my treatise on " Stethometry," I examined the con- 

 densed aqueous vapour of the breath, in health and disease, and 

 ascertained the quantity of organic matter that it contained. The 

 breath, of fifteen healthy persons and of twenty- seven cases of disease 

 was examined chemically by Wauklyn's method of water analysis, 

 and microscopically. The fact of chief importance obtained was, that 

 every specimen contained a small, but appreciable, quantity of both 

 free and organic ammonia. The quantity from the cases of disease 

 varied considerably, but that from healthy persons was remarkably 

 constant, varying from 0*325 milligram to 45 per 100 minims of 



