HISTOLOGY OF NERVES. 89 
Tease a small piece of fresh nerve in chloroform: this will 
partially dissolve the fatty medullary sheath and so render clearly 
vesible :— 
i. The primitive sheath, or sheath of Schwann. 
ii, The axis cylinder. 
b. Non-medulated nerve fibres. 
Examine mounted preparation of frog's cornea stained with 
chloride of gold: note the fine varicose nerve fibres with no 
medullary sheath. 
2. Nerve cells: Tease in glycerine a small fragment of the 
anterior cornu of the spinal cord of the ox (lumbar region). cover, 
and examine with low and high powers: note 
i. The nerve cells; large nucleated cells with many 
branching arms. 
ii. The nerve fibres. 
iii, The fine connective tissue binding the several parts 
together. 
3. Structure of the Spinal Cord. 
Take one of the prepared transverse sections of spinal cord of 
frog: mount in balsam, and examine with low and high powers : 
note :— 
a. With low power. 
i, Shape; bilaterally symmetrical ; considerably wider 
than it is deep. 
ii. The ventral or anterior, and dorsal or posterior 
fissures: of these the anterior is broad and 
shallow, the posterior narrow and deep. 
iii, The white matter: forming the outer part of the 
cord, and composed of medullated nerve fibres. 
iv, The grey matter; forming the central part of the 
cord, and composed of a dense network of non- 
medullated nerve fibres, in which are imbedded 
numerous nerve cells, 
