ELEMENTS OF NERVOUS TISSUE. 65 



vous ganglia (PL XIII. fig. III.). The nerves are not 

 very rich in blood-vessels ; they form a net-work of 

 large meshes, the terminal branches from which ra- 

 mify in the neurileinrna ; they do not come directly 

 in contact with the naked primitive fibre (Kolliker). 



In addition to the nerve cells, which constitute 

 their most important element, nervous ganglia con- 

 sist of an intermingling of very delicate connective 

 fibres with oval nuclei, and a large number of blood- 

 vessels (PI. XIII. fig. III.). The connective element 

 is the same which has been already mentioned as 

 forming the thick nucleated external or second enve- 

 lope of certain nerve cells, and the sympathetic nerve 

 fibres of Remak are also derived from it, for their 

 constituent elements are identical in form, and be- 

 have similarly under the influence of chemical 

 reagents. 



It is generally conceded that nervous ganglia con- 

 tain all of the different forms of nerve cells. In those 

 of the spinal nerves, cells with two branches (bicau- 

 date) are most numerous, and of these there are two 

 kinds. The one have their prolongations given off 

 from diametrically opposite points of their circum- 

 ference, one being continuous with a nerve fibre from 

 the spinal marrow, and the other with a peripheral 

 nerve (PL XII. fig. III.). The other kind of bi-cau- 

 date cells give off both of their prolongations in the 

 same direction, and always towards the surface. 

 Finally, the cells with but one prolongation (uni- 

 polar) are always continuous with a peripheral fibre. 

 In the ganglia of the sympathetic system most of the 

 multi polar nerve cells seem to send off the same 



