THE SYMPATHETIC DIVISION OF THE NERVOUS SYSTEM 155 



single axon which also enters the nerve trunk as a non-medullated nerve 

 fiber, but may later acquire a very thin medullary sheath, perhaps sen- 

 sory neurons. The dendrons of the second type are distinguished from 

 those of the first by being very long and slender and also by entering 

 the nerve trunks, to pass, presumably, to neighboring ganglia. The 

 dendrons of the first cell type on the other hand, are shorter, thicker, 

 and end in relation with other cells within the same ganglion. Carpen- 

 ter and Conel report also intermediate types in the cat. 



In certain rodents (rabbit and guinea pig) many of the neurons of 

 the vertebral and pre vertebral autonomic ganglia are bi-nucleate (Car- 

 penter and Conel, Jour. Comp. Neur., 24, 3, 1914). 



The ganglionic cell group is excentrically placed as regards the axis 

 of the nerve trunk, some funiculi apparently passing the ganglion with- 

 out being in any way connected with its nerve cells. 



The sympathetic differ from the cerebrospinal ganglia chiefly in the 

 relative preponderance of non-medullated nerve fibers in the former and 

 of the medullated type in the latter. Just as the cerebrospinal ganglia 

 receive a few non-medullated sympathetic fibers, so also the sympathetic 

 ganglia receive, through the medium of the white rami communicant es, 

 a certain number of medullated nerve fibers from the cerebrospinal sys- 

 tem. Moreover, with the intense staining method of Weigert, very thin 

 medullary sheaths may now be demonstrated where formerly they were 

 not suspected. 



The sensory and motor neurons of the cerebrospinal division show 

 characteristic differences in their chromophilic substance. In the cere- 

 bral and spinal ganglia the cell bodies of the sensory neurons contain 

 fine Nissl granules evenly distributed throughout the cytoplasm. The 

 motor cell bodies from the spinal cord contain fewer and much larger 

 chromophilic flakes. The sympathetic neurons likewise present a charac- 

 teristic and constant appearance: the chromophilic granules are inter- 

 mediate in size and generally massed toward the periphery (Malone; 

 Carpenter and Conel). 



The ganglia are supplied with blood vessels and lymphatic vessels 

 in a manner similar to the nerve trunks in whose course they occur. 



The earlier conception of the nervous system interpreted the nerve 

 fiber (axon) as the fusion product of a chain of cells extending from its 

 proximal to its distal end. The axis cylinder fibrils were regarded as 

 differentiation products of the cytoplasm (Schwann; Apathy; et al.). The 

 view which now prevails interprets the axon as the outgrowth of the cell 

 body to which it is attached (His; Cajal; et aL). The tissue culture 



