LESSON X. 

 STEUCTUEE OF NERVOUS TISSUES. 



A. Spinal Nerves. 



1. Cut off about one-third of an incli of a small 

 perfectly fresh nerve (e. g. a branch of the sciatic 

 of a frog), and place it on a glass slide without 

 any fluid. Fixing one end by pressing on it 

 with the blunt end of a scalpel, pass a needle 

 through the other end in the direction of the 

 nerve fibres, and so spread it out into the shape 

 of a fan ; add a drop of normal saline solution, 

 and cover with the cover-slip. Observe 



a. The medullated nerve-fibres of variable 

 size. 



b. In each fibre the double contour, due to the 

 medullary sheath or white substance of 

 Schwann. 



c. The primitive sheath; this is seen with 

 difficulty except at points where the me- 

 dullary sheath has been displaced in mount- 

 ing. 



d. The connective tissue (endoneurium) running 

 amongst and round the nerve-fibres. 



