XV] PERIPHERAL GANGLIA AND NERVE CELLS 123 



osmic acid (cut in two longitudinally unless small) for J hour to 

 an hour ; wash with water. Remove to a mixture of equal parts 

 glycerine and glacial acetic acid for 3 to 4 days (frog) or 4 to 5 

 days (mammal). Tease out. It is better to take young than 

 adult animals because the connective tissue is less resistant in 

 the former; the rabbit is better than the cat or dog. 



The sheath can often be torn off bodily after treatment as 

 above from the ganglia on the trunk of the sympathetic, by 

 means of two strong needles. In the frog, the spinal ganglia 

 easiest to get are those on the 7th, 8th and 9th nerves. In many 

 mammals the 2nd cervical spinal ganglion can be obtained with- 

 out cutting open the vertebral canal. 



Hardening. For most purposes osmic acid 1 p.c. is the most 

 useful hardening agent. It may be noticed that a nerve cell in 

 certain states has a clump (sometimes two) of yellow-brown 

 stained sharp granules. For staining basophil substance the 

 ganglion should be placed in mercuric chloride 1 day ; alcohol 

 2 or more days, and cut in paraffin ; alcohol may be used alone 

 but it is apt to cause shrinking of the cells. (Cp. also p. 244.) 



In the rabbit and some other animals there are commonly 

 two nuclei in the sympathetic nerve cells. 



Changes in ganglion cells are described as occurring on 

 stimulation of the nerves running to them, but it is not easy 

 to satisfy oneself that they occur. For chromatolysis in nerve 

 cells in the central nervous system, cp. p. 242, Demonst. 5. 



In the frog peripheral nerve cells not hidden by pigment 

 may be obtained by taking the piece of the bladder which 

 immediately adjoins the cloaca ; cutting it open, and spreading 

 it out, outer surface uppermost ; it is best to expose the cloaca 

 by cutting through the symphysis pubis. 



Auerbach's ganglia may be seen in sections, taken parallel to 

 the outer surface of the intestine. The intestine is cut open, 

 flattened between glass slides and hardened in this position. 



For staining nerve cells with methylene blue for synapses, 

 cp. p. 321 ; and for staining them by the Qolgi method, cp. p. 240. 



The following modification of Golgi's method is recommended 

 by Kolossow for sympathetic ganglia in adults. Place the 



