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before the specific process, due to the introduction of the virus, has become 
visible to the naked eye. The vaccine lesion therefore develops in a 
skin practically normal and its evolution can better be studied than when 
the phenomena of repair of a scarification complicates the picture. A 
general anesthetic was employed whenever the operation might cause dis- 
comfort to the animal. 
Daily observations were recorded upon the constitutional reaction of 
the animal, the temperature reaction per rectum, the reaction of the 
lymph nodes, and the macroscopic appearances of the specific lesion. 
The material for histological study of the process in the skin was col- 
lected by excision of lesions. In many instances the animals were killed 
at various times after the inoculation. In these cases a complete autopsy 
was performed and the material saved both from the specific lesions and 
from the viscera. All tissues were put in Zenker’s Fluid for 24 hours, 
then washed in running water for 24 hours, and hardened by passage 
through graded alcohols. Material for histological study was embedded 
by the chloroform-paraffin method. Sections were stained in various 
ways. 
EXPERIMENTS IN DETAIL. 
The experiments on which this article is based comprise the inocula- 
tion with vaccine virus of 28 monkeys on the skin of the abdomen. ‘The 
following experiments are selected to be given in detail. 
I. Clinical course of the disease. 
No. 91. Adult male M. eynomologus. Inoculated in 12 places on the abdomen 
with vaccine virus No. 251. Body temperature 38°.5 C. 
Twenty-four hours after inoculation 2 scratches show slight elevation, others 
show no reaction. Body temperature 38°.2 C, 
Forty-eight hours. There is slight elevation and some opacity along the line of 
inoculation. The axillary lymph nodes are of normal size. Body temperature 
39° C. 
Three days. There is a distinct elevation with opacity and redness about the 
narrow erust which marks the line of inoculation. The axillary lymph nodes are 
slightly enlarged. The body temperature is 39° C. 
Four days. A distinct pink elevation is present, extending from 2 to 3 milli- 
meters on either side of the central crust. One lesion appears to be vesicular. 
Axillary lymph nodes distinetly enlarged. Body temperature 39°.5 C. 
Five days. The lesions present as rounded elevations from 4 to 5 millimeters 
across. The central crust is surrounded by a narrow translucent vesicle which in 
turn is bordered by a pink areola. Axillary lymph nodes markedly enlarged. 
Body temperature 40°.2 C. 
Six days. The lesions show the same features; but the extent is greater and the 
whole lesion more sharply circumscribed. Axillary lymph nodes enlarged. Body 
temperature 39°.5 C. 
Seven days. The lesions present a central yellowish crust which is bordered by 
a vesicle, translucent peripherally but opaque about the crust. The lesions are 
surrounded by a distinct red areola. Axillary lymph nodes enlarged and hard. 
Body temperature 39°.5 C. 
ie Pee we 
ie 
