I2 + 
THOMPSON YATES LABORATORIES REPORT 
placed in the sunshine, two also in the shade, and two were kept in the dark. The 
details are given in Table IV ; after exposure to six hours' sunshine, both wet and 
dry samples contained no B. coli in the quantities analysed ; of the shade samples, 
the wet one contained 247,000 per grm., while in the dry sample there was no 
B. coli. No 5 was scarcely dry by the evening of the first day ; on the next day, 
however, it also contained no B. coli. The two samples 5 and 6 were then left for 
nearly two months, at the end of that time, while No. 5 was sterile as regards B. coli, 
No. 6, which had been kept moist all the time, contained 566,000 per grm. Though 
at the commencement of the experiments care was taken to exclude all other organisms 
by sterilising, no attempt was made to keep the contents of the dishes sterile after- 
wards, thus attempting to approximate to the conditions which obtain in nature. 
Experiment II — (Table IV, b), consisting of two samples only, a wet and a 
dry one, both exposed to sunshine, was made to correct a discrepancy in Experiment 
I. After the analysis on July 27, the two Petri dishes with their contents were 
placed in a dark cupboard, and after nearly two months were again analysed. The 
result was the same as in Experiment I ; while in the dry sample B. coli was absent, 
in the wet one it was present to the extent of 47,000 per grm. 
Experiment III was made when there was not so much sunshine, and that 
rather intermittent ; it, however, also illustrates the marked difference in the length 
of life of B. coli under dry and wet conditions. 
Some experiments were also made with a pure culture of B. coli in order to 
find its length of life when dried upon filter paper. Scraps of sterile filter paper, 
about an inch square, were dipped into a ' peptone-salt' culture, twenty-four hours 
old, of B. coli, and these were drained and then laid upon a sterile Petri dish. The 
pieces of paper were just the same size, and hence retained approximately the same 
number of organisms. They were placed under a tightly-fitting bell-jar, and a current 
of dry air was drawn over them by means of a pump, so that they were quickly dried. 
From time to time, one of these pieces of paper was removed and incubated with 
10 c.c. nutrient broth ; after twenty-four hours plates of ordinary nutrient agar were 
made of ice. of the broth and these examined, after forty-eight hours' incubation, 
to see if they were sterile. It was found that there had remained no B. coli in the 
piece of paper which had been dried for twenty-eight hours, while B. coli was almost 
entirely killed after twenty-three and a quarter hours exposure to the current of dry 
air. A culture of B. coli commune from the original strain of Escherich was 
used for these experiments, kindly given me by Dr. H. E. Durham. Experiment II 
gave a similar result ; after twenty-four hours' exposure of the pieces of paper 
to a current of dry air, all the organisms were found to have been killed. An 
interesting series of plates can be obtained by taking the dried pieces of filter paper 
at different times, moistening them with sterile water and pressing them on the 
surface of an already poured agar plate for a few minutes ; then the paper should be 
