THE CENTRAL NERVOUS SYSTEM 381 
relation to one another. This character is quite in accord 
with certain of the outbreaks in man. However we can- 
not state that the disease is exactly the same as seen in 
the human being for, as will be noted in the cited examples, 
all the pathological features were not fulfilled. 
It is not always possible to differentiate between 
myelitic disease and polyneuritis of man or animals. 
Studied symptomatically the cases in our records which 
proved to have degenerative and infiltrative lesions com- 
parable to poliomyelitis showed gradual but progressive 
paralysis expressed by inability to move, rather than dis- 
inclination — in other words loss of power rather than 
restriction because of pain. None of the animals in 
which poliomyelitis was. demonstrated have exhibited the 
ataxia of the hind legs discussed on a previous page nor 
have we found myelitic lesions in the few cords from 
animals suffering with this weakness. The nearest ap- 
proach to a cerebrospinal explanation for weakness and 
palsy was in a zebra which died with constipation, acute 
nephritis, and hepatic perilobular fibrosis. In this animal 
a pronounced subpial mononuclear infiltrate was ob- 
served, in places invohdng the superficial parts of the 
cerebral gray matter, especially about the congested 
vessels of this area. This condition was present to a 
slight degree in the cord. There was then a low grade 
meningoencephalitis but no nerve cell changes. So far as 
is known to me no animal showing a definite local paresis 
or paraplegia, recovered from the attack; had this 
occurred we might have observed residual palsies. 
In so far as lesions are concerned they are perhaps 
best illustrated by the appended cases, but since even in 
them there is a lack of uniformity, it may be well to 
discuss the basic changes of all. The outstanding 
abnormality in the microscopic anatomy is the richness 
of small mononuclear cells beneath the pia, both spinal 
and cerebral, around the smaller blood vessels and to a 
lesser extent around the multipolar cells of the gray 
