Nervous Structures. 75 



NEKVOUS STEUCTUEES. 



MEDULLATED NERVE FIBRES. 



Dissect out the sciatic nerve of a frog and stain for a 

 few minutes in half per cent, solution of nitrate of 

 silver, wash well and expose to the light in distilled 

 water until it has become of a brown colour ; cut small 

 portions and gently tease out so as to separate the 

 fibrils, this must be done carefully in a drop of gly- 

 cerine on a slide ; cover and examine. 



NODES OF EANVIER. 



These will be found marked by black crosses in the 

 course of the nerve fibre, the silver being heavily de- 

 posited at the node and penetrating a short distance 

 either way giving the appearance of a cross. These 

 nodes can be seen in the fresh nerve or in nerve hard- 

 ened and stained in the ordinary manner. 



HARDENING NERVES. 



Take any of the larger nerves from the animals used 

 for material and harden some in 2 per cent, bichromate 

 of potash, page 13 ; others in chromic acid mixture. 

 Cut longitudinal and transverse sections of each of these 

 and stain with logwood, mount in Canada balsam. 



