NINTH ANNUAL SREPORT: 151 
the disease should have been so long considered as one primarily 
of the nervous organs, since in the study of these animals it is 
often impossible to properly inspect or palpate them, and we are 
more dependent on the study of the movements of the animals. 
From simple observation alone, one cannot fail to be impressed 
with the idea that the disease is chiefly a muscular or nervous 
disorder, and it is only when we are able to closely inspect the 
animals that the earlier changes in the bones with their deformi- 
ties can be made out. In reviewing the literature-of osteomalacia 
as it occurs in man, we have been struck with the meagre account 
of the nervous lesions which accompany the disease in the human, 
probably because the prominence of the osseous changes has 
overshadowed them. Many otherwise careful descriptions of the 
disease entirely omit this important system. 
It is probable that the malnutrition and anaemia which accom- 
pany the disease are largely responsible for the lesions of the 
central nervous organs, but these alone, to our minds, do not 
satisfactorily explain all the changes which we have found in 
the brain and spinal cord. Doubtless the deformity of the spinal 
column with pressure on the cord, posterior root gangha and 
nerve roots, causes certain of the lesions, but in our opinion there 
is a still more close relationship existing between the disease and 
these alterations which may be directly and independently pro- 
duced by the essential etiological factors. We are as yet unable 
to give a plausible explanation of this relationship. It seems 
to us most likely the changes develop secondarily or after the 
bony lesions are comparatively well advanced, since in one in- 
stance, one of the earliest cases studied by us (case X) no de- 
generative alterations of the spinal cord were found. Again the 
great variation in the affected tracts noted in our cases would 
apparently indicate that the disease was not a primary or specific 
one of the central nervous system for the lesions are not con- 
stant but variable. 
The alterations found in the brain consist of chromolitic 
changes in the ganglion cells, and of a dilatation of the lymph 
spaces associated with more or less congestion of the cerebral 
vessels. The degenerative factors seem to have a particular selec- 
tion for the cells of the motor cortex, if we may judge from the 
changes found in the spinal cord. 
In the cord the most common lesions noted by us have been 
degenerations of various tracts, most constantly of the direct and 
cross pyramidal tracts; also the columns of Gall and Burdach 
(see case reports). Lesions simulating those of poliomyelitis 
