No. 7. DEPARTMENT OF AGRICULTURE. 187 



MICROSCOPIC EXAMINATION 



The distinct changes in the cellular structures of the verebral 

 hemispheres, cerebellum, spinal cord and nerve ganglion accompany- 

 ing the development of rabies were pointed out in the early seventies, 

 but Babes in 1892 was the first to search for these tissue changes 

 in animals dead of rabies to assist in the establishment of a diagnosis. 

 He held that it was possible to make a rapid diagnosis by a micro- 

 scopic examination of the medulla oblongata and spinal cord, de- 

 scribing the cellular accumulation in these structures under the 

 name of "rabic tubercle." Following the discovery of the "rabic 

 tubercle" by Babes, Nelis in the laboratory of Van Gehuchten, found 

 changes in the spinal cord and gangion of two human beings dead of 

 rabies. Ravenel and McCarthy*' emphasized the diagnostic import- 

 ance of these tissue changes in 1900, and expressed themselves of 

 the opinion that the examination of the ganglion in the dog for the 

 changes described by Van Gehuchten and Nelis afforded an accurate 

 means to a rapid diagnosis of rabies. These changes pointed out by 

 Van Gehuchten and Nelis in the ganglion and those of Babes in the 

 medulla oblongata and spinal cord are the result of the influence 

 of something thrown off by the cause or virus of rabies upon the 

 virus of rabies upon the endothelial cells and nerve cells of these 

 structures, directly or indirectly. The andothelial cells forming the 

 walls of the cappillaries and the single layer of the endothelial cells 

 which make up the lympth sacs suriounding the larger nerve cells of 

 the spinal cord and those of the nerve ganglion are chiefly involved. 

 These cells are apparently stimulated to proliferate and the increase 

 in the cells causes a thickening of the walls of the capillaries aud 

 lymph sacs. Along wath these endothelial changes, slightly in ad- 

 vance, the nerve cells undergo degenerative changes — shrinkage, chro- 

 matolyses and as the endothelial cells crowd in upon and over the 

 nerve cells, complete destruction of the nerve cell is the result. (See 

 plate TIT). Crocq followed by Spiller', was among the first to show 

 that endothelial cell ju'oliferation with nerve cell degeneration and 

 destruction is seen in some conditions, without the existence of rabies. 

 This has been the experience of others and the writer in the study of 

 forage poisoning or cerebrospinal meningitis of horses has seen typi- 

 cal "rabic tubercles" in the medulla oblongata, and in several dogs 

 with distemper, endothelial cell proliferation changes were found in 

 the ganglion. 



