TEE PERIPHERAL NERVE-ENDINGS 



223 



numerous processes, suggest a spider and its legs (Figs. 139 and 

 155). Some forms are described as "moss -like." Neuroglia- cells 

 are well shown in silver -stained specimens. The neuroglia of the 

 spinal cord is intimately related with the epithelium lining the 

 central canal, from which it originated. Neuroglia, unlike the 

 other supporting tissues, is derived from the ectoderm. 





THE PERIPHERAL NERVE-ENDINGS 



The terminal branches of the nerves are so complex in struc- 

 ure and so difficult of demonstration that only a few of the most 

 important can be considered in this work. 



Sensory nerves sometimes present free endings, as in the strati- 

 fied epithelium of the epidermis and cornea. The medullated nerve- 

 fiber loses its medullary sheath at a node of Ranvier, and divides 

 repeatedly, making a plexus of minute fibrillae in the connective 

 tissue, or just below the epithelium, or between the epithelial cells. 



Special sensory endings are more complex in structure. 

 Examples are found in the tactile corpuscles, which occur in the 

 papillae of the skin. They are oval bodies having numerous nuclei. 



TERMINATION OP NERVE -FILAMENTS IN THE EPITHELIUM OF THE CORNEA. 

 (RANVIER.) 



One or more medullated nerve -fibers enter at the base, losing their 

 medullary sheaths. The axis -cylinders break up into fibrils, which 

 here and there present expansions. 



The Pacinian bodies or corpuscles of Vater are easily found 

 in the mesentery of the cat, where they are numerous and visible 

 to the unaided eye. They are oval in form and nearly transparent. 

 The most prominent part is the capsule, which consists of lamellas 

 of connective tissue, which are concentric, and resemble the layers 



