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vaccinial lesion, In this respect variolous keratitis in the monkey ap- 
proaches more nearly to vaccinial or variolous keratitis in the rabbit 
than does vaccinial keratitis in the monkey. 
The small part played by the polynuclear leucocyte in the variolous 
keratitis contrasts strongly with the prominence of this cell in the 
specific cutaneous lesions of the disease in the monkey. It seems probable 
that in the skin inoculation the presence of a large number of these cells 
is conditioned by the destruction of tissue incident to the inoculation and 
that they continue to be attracted, not so much by the variola organism 
or its products as by the presence of substances set free in the process of 
cell destruction incident to the activity of the parasite and the other 
organisms which gain access to the lesion. As all such degeneration 
products are retained at the site of inoculation by the crust, in the case 
of a cutaneous lesion, while they readily escape in the case of the corneal 
one, It is easy to understand why in the former case large numbers of 
leucocytes pass from the vessels to the lesion. 
The absence of nuclear phases of cytoryctes variole in the corneal 
lesion was disappointing. It is possible that there is some inherent dif- 
ference in the cells of the cornea which makes them unsuitable for the 
development of the parasite beyond the cytoplasmic stage, though we 
are inclined to regard the absence of nuclear forms in these lesions as 
being due to the action of physical factors. In a typical corneal lesion 
the cells are probably cast off from the surface before the nuclear forms 
are produced. It is possible that oblique incisions into the corneal sub- 
stance, in which islands of epithelial cells would be retained, might show 
a development of the nuclear forms of the parasite. 
In a previous section we have shown that the endothelial cells of 
capillaries beneath the primary skin lesions of variola inoculata are 
invaded by cytoryctes. From this we have been led to believe that some 
such process is involved in the dissemination of the organisms to form 
the exanthem. From the considerations of the time elements it seems 
probable that such infected endothelial cells are set free at an earlier 
stage in the disease than the demonstration of the infected endothelial 
cells beneath the primary lesion. The fact that an exanthem follows the 
development of a lesion in the nonvascular cornea, where extension of 
the process to blood vessels does not occur, suggests that the distribution 
of the organism, if brought about through the intermediation of endo- 
thelial cells, is due to an infection of the cells which line lymph channels. 
CONCLUSIONS. : 
(1) Inoculation of the cornea of the monkey (M. cynomologus) with 
variola virus produces a specific lesion characterized by swelling, prolif- 
eration, and varying degrees of degeneration of the epithelial cells. 
‘Q@) The lesion is similar to that produced by inoculation of the cornea 
of the rabbit with vaccine or with variola virus. 
