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The reaction of the corium is evidenced by some infiltration, with polymorpho- 
nuclear leucocytes and a certain degree of swelling of the endothelial cells lining 
the blood vessels and lymphatics of the corium adjacent to the site of the in- 
oculation. Immediately beneath the lesion endothelial cells of lymphaties and 
of capillaries were found which contained in their protoplasm cytoplasmic phases 
of Cytoryctes variole. 
The epithelial cells of the lesions contain many stages of the parasite. Both 
the cytoplasmic and the nuclear phases were well represented. 
Seven and eight days. Lesions of these durations showed the same charac- 
teristics as did that described above. The vesicle becomes more extensive and the 
necrotic area beneath the crust larger. The coalescence of the lateral vesicles 
often left single cells or islands of cells in a fair state of preservation, which were 
to be found in various stages of agglomeration on the way to the formation of 
trabecule, or partitions in the large vesicle. 
Viscera. Histological study of the internal organs did not reveal any lesions 
of a variolous nature. All through the organs, wherever blood vessels were cut, 
short bacilli having the morphology and staining peculiarities of the bacillus of 
hemorrhagic septicemia were readily demonstrable. 
SUMMARY. 
The evolution of the primary lesion at the site of inoculation with 
variola virus in the orang-utan is similar to that which follows the 
inoculation in the monkey and in man. The thickness and the deep 
pigmentation of the skin of this animal rendered the appearance less 
characteristic to the naked eye than in Macacus cynomologus. 'The death 
of the animals, of intercurrent disease, before a general exanthem might 
be expected to develop, deprived us of data upon this point. Both 
animals showed a marked constitutional reaction, but this, because of the 
existence of an intercurrent disease, can not be interpreted as resulting 
from the smallpox process. 
The histological study of the primary lesions and of the viscera of 
the orang-utan inoculated with variola virus shows the process to be 
essentially similar to that which follows inoculation of the monkey with 
the same virus. There seems to be some difference in the degree of 
reaction in the corium beneath the primary lesion, it being notably less 
in the orang-utan. -The histogenesis of the cutaneous vesicle is similar 
and we note the absence, as in the monkey, of focal lesions in the bone 
marrow. The most striking thing about the primary lesions seems to 
be their richness in nuclear forms of cytoryctes. ‘This matter will be 
taken up in detail in another paper and so will not here be further 
commented upon. 
CONCLUSIONS. 
(1) The orang-utan is susceptible to variola inoculata. 
(2) The evolution of the specific lesion at the site of inoculation is 
comparable with that which follows similar inoculations in the monkey 
(M. cynomologus and M. nemestrinus). 
(3) The primary lesions of variola imoculata in the orang-utan stand 
closer to the cutaneous lesions of variola vera in man than do the primary 
