279 
No. 325. Collected November 3 from a case of mild variola vera in a native 
boy, aged 8 years, on about the tenth day of the disease. 
No. 326. Collected November 6 from a case of severe variola vera in a native 
boy, aged 12 years, on about the eighth day of the disease. 
No. 327. Collected on November 9 from a case of severe variola vera in a native 
girl, aged 11] years, on about the ninth day of the disease. 
Method of inoculation.—The introduction of the contagion i: to the 
animal was effected by making a number of separate shallow scratches 
with the point of a scalpel on the previously shaved and cleaned skin of 
the abdomen, and rubbing the virus into the wound with the back of the 
instrument. ‘The inoculations were placed at least 2 centimeters apart. 
The usual precautions were observed to avoid the introduction of extrane- 
ous matter. An anaesthetic was employed whenever discomfort might 
otherwise be caused to the animal. 
The animals were observed daily during the course of each experiment. 
The appearance of the lesions to the naked eye at the sites of inoculation 
was recorded, together with the occurrence and evolution of the exanthem, 
the constitutional reaction, the body temperature taken per rectum, and 
the reaction of the lymph nodes. 
Material for histological study was obtained either by excision of the 
lesions during the course of the experiment, or by autopsy when the 
animal was killed. All tissues were fixed in Zenker’s fluid for twenty- 
four hours, washed in running water over night, and then hardened by 
passing through alcohols of graded strength. Tissues were embedded by 
the chloroform-paraffine method. Sections were cut on the Minot micro- 
tome of a thickness of from 3 to 6 microns, and were stained in a variety 
of ways. 
In certain experiments the immunity of the animal, resulting from the 
first inoculation, was tested by subsequent skin inoculations with vaccine 
or variola virus. 
This section is based upon the study of sixty-five monkeys inoculated 
on the skin with variola virus, of which the following experiments are 
selected to be given in detail. 
1. Clinical course of the disease. 
No. 114. Adult, male, Macacus cynomologus. Monkey was inoculated in 12 
places on the skin of the abdomen with virus No. 167 (vesicle contents). Body 
temperature 37°.6 C. 
Twenty-four hours after inoculation the scratches show a narrow, dry crust, 
about which the skin is opaque and slightly elevated for a distance of 1 or 2 
millimeters. Body temperature 39°.2 C. 
Forty-eight hours. The skin for a short distance about the crusts is white, 
but this area fades, without a definite line of demarcation, into the surrounding 
normal skin. Body temperature 38°.2 C. 
Three days. The elevated skin about the crust is pink for a distance of 2 
millimeters. Axillary lymph nodes slightly enlarged. Body temperature 39° C. 
Four days. The lesions are present as rounded, pink elevations with fairly 
definite borders and surmounted by delicate yellow crusts. The lesions average 
