112 ELEMENTARY PHYSIOLOGY. [x. 



seen issuing. Cut through the bone from the 

 middle line to the place where the nerves issue, 

 turn the piece of bone forward, and gently scrape 

 out the brain. 



A filament (the fifth nerve) will then be seen 

 going towards the branches spoken of above. 

 Between the two is a slight enlargement, the 

 Gasserian ganglion, surrounded by tough con- 

 nective tissue and by connective tissue attached 

 to the bone. Cut away this tissue and excise 

 the ganglion. 



Tease it out a little in '25 p. c. osmic acid 1 , leave 

 it in the acid for about half-an-hour, then wash, 

 and place it in strong Frey's carmine for a day ; 

 wash, and tease out in glycerine, during the 

 teasing examine from time to time under a low 

 power and throw away the fragments which 

 'consist of connective tissue only. 



Instead of the Gasserian ganglion a spinal gan- 

 glion from a frog or mouse may be taken. In 

 the frog the spinal ganglia are surrounded by a 

 chalky mass; when this is removed the ganglion 

 can be seen as a greyish semi-transparent bulg- 

 ing on the nerve, the 7th, 8th, 9th are easiest 

 to obtain. 



Examine carefully the more isolated cells ; here 

 and there one will be seen with its cell substance 

 prolonged into a process ; from most of the cells 

 the process will probably have been torn away 

 in teasing. 



1 Or it may be placed in potassium bichromate -2 p. c. for two or 

 three days and then teased out. 



