X.] STRUCTURE OF NERVOUS TISSUES. 109 



Numerous small medullated fibres will be 

 seen mingled with the non-medullated fibres. 

 Compare the size of the medullated fibres 

 here and in the sciatic nerve (A, 1). 



C. PERIPHERAL COURSE OF NERVES. 



1. In the specimen prepared Less. VIII. 6 : observe 



a. Under a low power, the nerve running across 

 the lower part of the muscle and sending off 

 fibres or bundles of fibres at intervals and so 

 spreading out over it. 



b. Under a high power, that where the lateral 

 bundles (especially the smaller ones) are 

 given off, one or more of the nerve fibres 

 divide into two fibres, the division taking 

 place at a node. Trace a small bundle of 

 nerve fibres, the nodes are very close together. 

 Each nerve fibre apparently ends abruptly 

 over a muscle fibre ; in this specimen it can 

 only be traced as far as the blackened me- 

 dulla extends. 



2. Make a gold chloride preparation of the cornea 1 



1 The mesentery of the frog may be taken instead of the cornea, 

 but it is more difficult to obtain a good preparation. The mesentery 

 of the lower coil of the small intestine is pinned out with the 

 intestine, and placed in gold chloride -5 p.c. for about half-an-hour, 

 it is then well washed, the intestine cut away, and the mesentery 

 exposed to light in acidulated water. The larger nerve bundles, 

 containing a few medullated fibres, accompany the larger arteries 

 and form coarse and fine plexuses of non-medullated fibres as in the 

 cornea, but there are many more nuclei, even very small fibres 

 having nuclei on their course ; varicose fibrils like those of the cornea 

 will probably not be seen. 



