n8 
THOMPSON YATES LABORATORIES REPORT 
such experiment I have found is in a paper by Concornotti. (Centralhl. f. Bakt. 
XXVI, S. 492). He exposed in various places agar plates that had .already been 
poured, and incubated them ; he then made an emulsion with sterile water of the 
mixed cultures he obtained, and injected it intravenously into rabbits. In five cases 
out of forty-six he obtained cultures of B. coli from the organs and heart blood of the 
dead animal ; he concluded that this bacillus was present in the emulsion injected, 
and, hence, in the original air examined. The conclusion, however, appears to be 
quite unwarranted, for the researches of Lesage and Macaigne {Arch. d. Med. Exp. 
1892, p. 250), Ac hard and Phulpin {Arch. d. Med. Exp. 1895, p. 25), and notably 
those of Beco {Ann. d. f Inst. Past. 1895, p. 199), have conclusively proved that 
B. coli, normally found only in the intestines, is in the habit, both just before and 
also after death, of invading the organs and even the peripheral circulation. It is 
significant that most of the experiments of the last-named author were also made 
upon rabbits. Thus the presence of B. coli, as found by Concornotti, by no means 
proved that this bacillus had been the cause of death, or that it had been artificially 
introduced into the circulation. 
I have made a careful examination of the air in different places, but only on 
one occasion have I isolated B. coli, and that was from the air of an ill-ventilated 
stable. 
Soil, Road Dust. — I have never found the bacillus in virgin soil, and in 
cultivated manured lands, where it had been added artificially, I have also found it 
to be absent, a fact which I take to be due to the low power of resistance which 
B. coli possesses. This is also shown by the almost invariable absence of B. coli in 
dry samples of road dust, while it occurs in quantity in road puddles or in wet 
samples of dirt taken during rainy weather. This led me to make some special 
experiments to illustrate this point, and I found, for example (Table IV, b) that a 
mixture of a B. coli culture with soil, which contained more than 1,000,000 organisms 
per grm., after seven and a half hours' drying in the sun had all its organisms killed, 
while a similar sample, which was kept damp, had its numbers lowered only to 380,000 
per grm. These experiments are fully described at the end of the paper, and indicate a 
conclusion that the presence of B. coli not only is significant of pollution, but shows 
that the pollution must have been recent. 
The method used for these experiments has been already described in detail, 
viz. : — plating the sample with carbolized agar, incubating for forty-eight hours at 
42' C, counting the colonies which resemble B. coli, if present, and isolating and iden- 
tifying them. For identification I have found the coagulation of milk with the pro- 
duction of acid and the fermentation of lactose the two most distinguishing reactions 
of B. coli.* A medium containing the latter is conveniently made by simply adding 
to tap water 2 % of peptone and 1 % pure lactose ; this is distributed in Durham's 
* Harvey dishing, Johns Hofi/ins Hospital Bulletin, July, i goo. 
