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DISCUSSION, 
In considering the results of the preceding experiments certain points of 
considerable theoretical interest present themselves for discussion. Per- 
haps the most prominent feature of the disease vaccinia is the specific 
immunity which it produces. At it is hardly possible to consider this 
immunity without at the same time dealing with variola, we have decided 
to discuss this phase of the disease in a separate section. There remains 
for consideration here the clinical feature of the disease vaccinia as it 
occurs in Macacus cynomologus. In our experiments we have found 
that this species of monkey reacts to an inoculation with vaccine virus on 
the skin by a definite sequence of phenomena which are reproduced in 
each experiment with only very slight modifications. It is true that cer- 
tain animals do not react in exactly the same degree as do others, but 
these “abortive” reactions seem to us to depend upon conditions of natural 
immunity and to differences in the virus used for inoculation, and so do 
not affect the truth of the general statement that this species is markedly 
susceptible to the disease. 
Comparing vaccinia in M. cynomologus with vaccinia in man and in 
the calf we see that we have a strict parallel. We find a lesion developing 
at the site of inoculation which runs a definite course and heals after a 
fairly constant interval. This local lesion is associated with enlargement 
of the lymph nodes. Only those nodes are affected which are interposed 
between the areas of the skin on which the lesion develops and the main 
lymph trunks. During the active evolution of the local lesion there is a 
general reaction of the inoculated animal as shown by a rise in the body 
temperature. ‘The primary lesion is shown to exist at the site of inocula- 
tion from a very early period after the inoculation as a distinct process 
so that the latent period, before the lesion can be diagnosed by its ap- 
pearance to the naked eye, is shown to be rather apparent than real. 
Two things serve to differentiate the vaccine process from that follow- 
ing inoculation of variola virus on this species of monkey: First, in 
vaccinia we have never observed an exanthem; second, the temperature 
reaction is not so definite in its onset as in variola inoculata. 
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