110 PRACTICAL HISTOLOGY [XIV 



passing between the nerve bundles; it consists of 

 areolar tissue (Less. x.). 



The perineurium surrounding the nerve bundles, 

 consisting of two or more concentric nucleated mem- 

 branes. 



The endoneurium between the nerve fibres, con- 

 sisting of a small quantity of fine fibrous tissue. 



The cut ends of the nerve fibres varying in diameter, 

 and in each the section of the stained axis cylinder 

 surrounded by a transparent ring indicating the former 

 position of the medullary sheath, which has been 

 dissolved or made transparent in the process of mount- 

 ing. The primitive sheath as a limiting circle. 



7. Cut through the skin of the frog in mid dorsal line. 

 Cut out one of the small dorsal cutaneous nerves issuing from 

 the muscles of the back and running to the skin. Place it in 

 2 p.c. nitrate of silver for 5 to 10 minutes. Wash in water and 

 expose to light for about | an hour. Dehydrate and mount in 

 balsam. Note the layer of epithelioid cells shown by the 

 staining of their cement substance covering the nerve. The 

 nerve will be seen taking a somewhat sinuous course inside 

 the epithelioid sheath. 



8. Sympathetic Nerves. Cut out from the fresh 

 spleen of a large animal (e.g. ox) a small piece of one 

 of the large sympathetic nerves running alongside the 

 blood vessels. Remove the connective tissue sheath, 

 and tease out the nerve carefully in normal saline 

 solution. Note 



a. The scanty medullated nerve fibres. 



6. The non-medullated nerve fibres constituting 

 the bulk of the nerves. Add acetic acid to bring out 



