284 



THE INTERNAL ENVIRONMENT OF THE BODY 



Part III 



hypoglossal nerve will then regenerate along the pathway of the facial nerve 

 and will control the facial muscles (Table 16.1). 



Ganglia, Nerves, and Neuroglia 



A ganglion is a group of nerve cell bodies. In invertebrates, the ventral 

 nerve chain is a series of ganglia connected by nerves (Figs. 16.5, 16.6). In 



nerve 

 cords 



HYDRA 



PLANARIAN 



EARTHWORM 



GRASSHOPPER' 



Fig. 16.5. Nervous systems of representative invertebrates; except in hydra, 

 they are on the ventral side of the body, each one a series of ganglia connected 

 by nerves. They show the segmentation that is characteristic of the central nervous 

 systems and very evident in the arrangement of the human spinal nerves. (Cour- 

 tesy, Storer: General Zoology, ed. 2. New York, McGraw-Hill Book Co., Inc., 

 1949.) 



ganglion cells 



connective tissue 





Fig. 16.6. A small ganglion (autonomic). A cross section showing the bodies 

 of eight large nerve cells; //. cut ends of fibers of nerve cells; v, blood vessel with 

 blood cells. The ganglion is enclosed in a sheath of connective tissue. (Courtesy, 

 Nonidez and Windle: Textbook of Histology, ed. 2. New York, McGraw-Hill 

 Book Co., Inc., 1953.) 



