342 
No 48. Vesicle contents collected from a case in the Philadelphia epidemic dur- 
ing January, 1902, sealed in capillary tubes and exposed to the same conditions 
as the Boston disks, was found inactive when inoculated on the rabbit’s cornea 
4 months later. 
(b) The effect of drying upon variola virus—This series of experiments was 
undertaken to test the resistance of variola virus to drying at room temperature. 
For comparison, parallel experiments were made with vaccine virus. 
The ends of a number of glass rods were coated with a thin film of vesicle con- 
tents from a case of smallpox. Similar preparations were made from the five- 
day vaccine lesions of a calf. The rods were at once put into sterile test tubes, 
closed with cotton plugs, and kept at room temperature. 
After two weeks the rods coated with vaccine virus produced typical lesions 
on the monkey’s skin when rubbed upon a fresh scratch. The rods coated with 
variola virus were inactive. After three weeks the variola rods were again tested 
and found inactive. A final test of the vaccine rods three and a half weeks after 
preparation showed them to have also become inactive. 
(c) The effect of passage through the Berkefeld filter upon variola virus.—A 
sample of variola virus (No. 199, vesicle contents) was shown to be active when 
inoculated upon the skin of monkeys. A portion of the virus was filtered through 
a small Berkefeld filter, “N”. The filtrate was inactive when inoculated on the 
skin of 2 monkeys and on the cornea of 1 rabbit. The monkeys used in this test 
were later shown to be susceptible to skin inoculation with variola virus. The 
unfiltered portion of virus No, 199 was shown to be active for many days after the 
test of the filtered portion. 
(d) The effect of glycerin upon variola virus.—In a previous publication” we 
stated that we had found variola virus to be rendered inactive by mixture with 
glycerin. The following tests were made to control the results of our preliminary 
experiments along this line: 4 
No. 252. A large amount of variola virus (vesicle contents) was collected from 
a case of smallpox at autopsy. The material was put on ice and after 24 hours a 
portion of it was mixed with 60 per cent glycerin in the proportion of 1 part virus 
to 3 parts glycerin. The mixture was thoroughly shaken and kept on ice. The 
glycerinated virus was tested from time to time by inoculation on the monkey’s 
skin. 
No. 255. Monkey inoculated on the abdomen with the glycerinated virus after 
3 days on ice. A typical primary lesion developed, but its evolution was some- 
what delayed. An exanthem consisting of 2 typical lesions appeared on the 
tenth day. 
No. 273. Monkey inoculated on the abdomen with the glycerinated virus after 
11 days on ice. A typical primary lesion developed and was followed by an 
exanthem consisting of 3 small vesicles on the tenth day. 
No. 318. Monkey inoculated as before, with glycerinated virus which had been 
on ice for 26 days. A typical primary lesion developed which was delayed in its 
evolution and was not followed by an exanthem. 
No. 363. Monkey inoculated as before with the glycerinated virus which had 
been kept on ice for 50 days. The primary lesion was typical but delayed in its 
evolution. No exanthem developed. 
u Jour. Med. Research, 11, 296. 
