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the result of inoculation either with vaccine virus No. 1, 251, 236, 246, 
or 148 were selected for this experiment. Each animal was variolated on 
the skin of the abdomen with virus No. 52 or 200. No reaction followed 
the second inoculation. An interval of from 38 to 58 days elapsed 
between the two inoculations. 
3. Vaccination of the skin after variolation of the skin.—The results 
obtained in this series are best shown by presenting a number of the 
experiments in detail. 
No. 114, Adult male, M. cynomologus. Variolated on the skin of the abdomen 
with virus No. 167 (vesicle contents). Animal developed a typical variola inocu- 
lata including a general exanthem. On the thirty-seventh day after the variolous 
inoculation the monkey was vaccinated on the skin of the abdomen with virus 
No. 148. At the site of inoculation there developed a lesion which had all of 
the characteristics of a vaccine process only differing from primary vaccinations in 
the extent of the process and in the indefiniteness of the vesiculation. The lesions 
passed through a definite evolution and healed spontaneously. We had no hesita- 
tion in diagnosing the lesions as specifie but typical reactions. 
The experiment was repeated on 2 other monkeys of the same speciés with 
identical results, which need not be given in detail. 
No. 153. Adult male, M. cynomologus. The monkey was variolated in a number 
of places on the skin of the abdomen with virus No. 167 (vesicle contents). A 
typical, primary lesion developed, which, however, was not so extensive as in the 
other animals inoculated at the same time with the same virus. No exanthem was 
noted. 
On the tenth day of the experiment the animal was vaccinated on the skin of 
the abdomen with virus No. 148. An atypical reaction resulted, similar to those 
seen in the monkeys described above. 
On the twenty-fifth day the monkey was vaccinated on the skin of the abdomen 
with virus No. 1. An atypical lesion was again produced. 
No. 141. Adult male, M. cynomologus. Variolated on skin of abdomen with virus 
No. 167 (vesicle contents). Variola inoculata, with exanthem, developed. Twenty- 
eight days after the variolation the animal was vaccinated on the abdomen with 
virus No. 1. No reaction followed the vaccination. 
Two other monkeys were shown to be immune to vaccination of the skin with 
virus No. 1, 19 days after a variolation on the abdomen with virus No. 167 
(pustule contents dried with lycopodium), which had been followed by a typical 
primary lesion but no general exanthem. 
4. Variolation of the skin after variola inoculata.—This experiment was only 
undertaken in one instance and demonstrated the monkey to be immune, after a 
variola inoculata, to a second skin inoculation with variola virus. 
SUMMARY. 
(1) Vaccination of the skin in 13 monkeys protected against subse- 
quent vaccination of the skin. 
(2) A vaccination of the skin in 6 monkeys protected against subse- 
quent variolation of the skin. 
(3) A variolation of the skin in 3 monkeys protected against subse- 
quent vaccination of the skin. In the case of 3 monkeys the following 
vaccination yielded a positive, though an abortive, reaction. Another 
