NERVE TISSUE 



131 



Nerve cell bodies vary in size from very small cell bodies, such as 

 those found in the granule layers of the cerebellum and of the olfac- 

 tory lobe, to the large bodies of the Purkinje cells of the cerebellum 



and of the motor cells of the ventral 

 horns of the cord, which are among the 

 largest in the body. There is as much 

 variation in shape as in size, and some 

 of the shapes are characteristic of the 

 regions in which the cells are situated. 

 Thus, many of the bodies of the cells 



MA 





Fig. 74. Fig. 75. 



Fig. 74.^ — Scheme of Peripheral Motor Neurone. (Barker.) The cell body, 

 protoplasmic processes, axone, collaterals, and terminal arborizations in muscle are all 

 seen to be parts of a single cell and together constitute the iieiirone. c. Cytoplasm of 

 cell' body containing chromophilic bodies, neurofibrils, and perifibrillar substance; n, 

 nucleus; n', nucleolus; d, dendrites; ah, axone hill free from chromophilic bodies; 

 ax, axone; sf, branch (collateral); m, medullary sheath; n R, node of Ranvier where 

 branch is given off; si, neurilemma (probably not present in central nervous system); 

 m' , striated muscle fibre; tel, motor end plate. 



Fig. 75. — Large Motor Nerve Cell from Ventral Horn of Spinal Cord of Ox, showing 

 Chromophilic Bodies. (From Barker, after von Lenhossek.) a, Pigment; b, axone; 

 c, axone hill; d, dendrites. 



of the spinal ganglia are spheroidal; of most of the cells of the cortex 

 cerebri, pyramidal; of the cells of Purkinje, pyriform; of the cells of 

 the ventral horns of the cord, irregularly stellate. According to the 

 number of processes given ofT, nerve cells are often referred to as 

 unipolar, bipolar, or multipolar. 



The NUCLEUS of the nerve cell (Fig. 75) differs in no essential 



