NINTH ANNUAL REPORT. 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 ganglia and 

 nerve roots, causes certam 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 afifected 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 ]iarticular 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 l)y us have been 

 degenerations of various tracts, most constantly of the direct and 

 cross pyramidal tracts; also the columns of Gall and P>urdach 

 (see case reports). Lesions simulating those of poliomyelitis 



