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intervals, usually at 24-hour periods, from the time of the inoculation 
and the lesions and tissues fixed for histological study. All tissue was 
at once put in Zenker’s fluid for fixation and afterwards embedded in 
paraffin by the alcohol-chloroform method. Sections having a thickness 
of about 5 microns were cut, except in a few instances when sections of 
one-half this thickness were prepared. The Mallory eosin-methylene- 
blue method of staining gives very satisfactory results for the study of 
cytoryctes and was generally used. A large number of the staining 
methods now in common use were tried, but none was found to be 
specific for cytoryctes. 
The lesions upon which this histological study is based were obtained 
chiefly from Philippine monkeys (J. cynomologus) inoculated with 
vaccine or with variola virus. These were supplemented by variola 
lesions of the Java monkey (.V. nemestrinus), variola lesions of the orang- 
utan (Simia satyrus), and primary vaccinations from the human subject. 
The material furnished by the various series of experiments is as follows: 
1. Vaccine lesions of the skin.—Fifteen Philippine monkeys each with multiple 
vaccinations: A lesion excised at each 24-hour interval from 1 to 10 days after 
inoculation. Eleven other monkeys killed at various periods after vaccination. 
Two vaccine lesions of the human subject obtained 5 and 7 days, respectively, after 
vaccination. 
2. Vaccination of the cornea.—Nine monkeys furnishing lesions of 17, 24, and 
48 hours, and 3, 4, 5, 7, and 8 days’ duration. 
3. Vaccinations of mucous membrane.—Nine monkeys vaccinated upon the inner 
surface of the lip, on the nasal septum, and on the soft palate. Killed at 24- 
hour intervals from 1 to 9 days. 
4. Primary variola lesions of the skin.—Ten monkeys each receiving multiple 
inoculation: A lesion excised each day as in the skin vaccination series. Eleven 
other Philippine monkeys killed at various intervals after inoculation. Three 
Java monkeys: Lesions excised at 24-hour intervals from 3 to 9 days after vario- 
lation. An orang-utan furnished lesions 6, 7, and 8 days after variolation. 
5. Variolations of the cornea.—Nineteen monkeys. 
6. Primary variola lesions of the mucous membrane.—Nine monkeys variolated 
on the inner surface of the lip, on the nasal septum, and on the soft palate: Killed 
at 24-hour intervals from 1 to 9 days. Five monkeys variolated on the nasal 
septum alone: Killed 2, 3, 4, 5, and 6 days after the inoculation. 
7. Primary variola lesions of the trachea.—Kight monkeys. In one of these 
there was also a specifie process in the lung, possibly an extension from the 
trachea. 
8. Variola exanthem.—Lesions appearing at various locations upon the skin 
after an interval of 6 to 10 days after inoculation with variola. The eruption of 
one case in which it was profuse upon the mucous membrane of the oral cavity 
and esophagus as well as upon the skin. In this case there were also lesions of a 
specific nature in the seminal vesicle which were considered to be a part of the 
eruption. 
This material furnishes data on the occurrence of cytoryctes in lesions 
produced by the inoculation of three species of apes with variola, and in 
vaccine lesions of the Philippine monkey and of man. 
