cxviii Journal of Comparative Neurology. 



in the table. Thus the average thickness of the entire molecular layer 

 in the case of the three months' cat is about .286 of a millimeter, while 

 while that of the six months' cat is .;^^^ of a millimeter, an increase of 

 16"^ per cent." * * * "'■■' * *"' * 



"(4). It will be remembered that the ataxic kitten was three months 

 old when it began to manifest symptoms of disease. But, by reference to 

 the table, it is seen that the molecular layer is much thinner in the case of 

 the ataxic cat than in the normal three months' cat." 



"Arrested development alone cannot account for this. It is only 

 explained by an active atrophy." 



"(5). The distribution of the Purkinje cells. It is an interesting 

 fact in every normal specimen examined, the Purkinje cells were closely 

 packed together at the summits of the convolutions, where they were 

 found to be very numerous, while at the sides, as we passed toward the 

 base of the sulcus, the distance between these cells was found to increase, 

 and at the very bottom they stood quite far apart. This makes a direct 

 proportion between the thickness of the granular layer and the number 

 of Purkinje cells, as has been already suggested by others." 



"(6). Certain histological characteristics. ((?) Some sort of relation 

 exists between the peripheral processes of the Purkinje cells and the 

 small cells of the molecular layer, but this is only of a general nature. 

 (/>) In the degeneration ef the Purkinje cells, the processes more remote 

 from the cells are the first to be attacked, then this degeneration ap- 

 proaches nearer and nearer to the cell-body, which begins to shrink, 

 losing its nucleus, becoming smaller, until it drops out altogether, leaving 

 an empty cavity." 



Experimental Ascending Degeneration. 1 



After section of a peripheral nerve, medullary sheath and axis cylin- 

 der decompose and disappear. The nuclei of the sheath of .Schwann at 

 first multiply and then likewise disappear, leaving of the sheath only a 

 fibrous cord. These degenerative processes are explained by the theory 

 that the central organ exerts a trophic function, of which the part per- 

 ipherad is deprived by the section. 



1. Breqman, E. Uebor Experiiuen telle aufsteigende Degeneration luotorischer 

 and sensibler Ncrven. Arbeiten aus deni Institut f. Anat. n. Phy.s. des Centrahierv- 

 ensystenis. Vienna, 1892. 



