HISTOLOGY OF THE FROG 



91 



tinuity with the axial fibre of an efferent nerve of the ventral 

 root. The nerve-cells of the anterior horn are large, and are 

 called multi-polar because of their numerous processes, but 

 nerve-cells from other parts may be much smaller, and may 

 vary both in the number and the mode of attachment of their 

 processes. Thus there are bi-polar nerve-cells with two pro- 

 cesses, or uni-polar cells with one process only ; and in the 

 superficial layer or cortex of the cerebellum of mammals there 



Fig. 16. 



A , multipolar nerve ganglion cells from the spinal cord of an ox ; B, 

 portion of a medullated nerve fibre from the sciatic nerve of the 

 frog, highly magnified ; ax-^t axial filament ; N'J?, Node of 

 Ranvier ; n, neurilemma ; Sck, medullary sheath or white 

 sheath of Schwann ; JVu, nucleus. The preparation was treated 

 with osmic acid , which blackens the medullary sheath, and the 

 breaks in its continuity as shown in the figure are probably due 

 to the action of the reagent. 



are remarkable ganglion cells, called the corpuscles of Purkinje, 

 having a pyriform body, produced at the narrow end into 

 one or two stout processes, which immediately branch and 

 break up into a number of fine fibres, running with more or 

 less straight courses towards the surface of the cortex. The 

 broad end of the cell is usually produced into a single fine 

 fibril. A curious form of nerve-cell is found in the sym- 

 pathetic ganglia of the frog and of mammals. The cell-body 



Digitized by Microsoft® 



