260 THE BIOLOGY OF THE ANIMAL 



cells. Apply acetic acid. Treat another prepa- 

 ration with an aqueous solution of hEematoxylin. 

 2. Striated muscle. — Remove a portion of the 

 gastrocnemius and examine as above. Notice 

 that the muscle consists of fibres. In the latter 

 look for the striations, the nuclei, and the 

 membrane or sarcolemma. Treat one prepa- 

 ration with acetic acid, another with magenta. 



g. Nervous tissue. 



1. Nerve fibres. — Eemove a piece of the sciatic or 



other large nerve and carefully tease it in a drop 

 of salt solution. Note the medullated nerve 

 fibres held together by a membrane, the peri- 

 neurium. Examine a single fibre and endeav- 

 or to make out the surrounding membrane, 

 called the primitive sheath or sheath of 

 Schwann. Within this is the medullary 

 sheath. The former is best seen in fibres 

 which have been torn. In such fibres look also 

 for the axis cylinder, projecting beyond the 

 medullary sheath. Treat a preparation with 

 chloroform, which will partially dissolve the 

 fatty substance forming the medullary sheath, 

 and thus make the primitive sheath and the 

 axis cylinder more plainly apparent. 



2. Nerve cells. — Eemove a spinal ganglion and 



tease it in eosin. Examine the preparation for 

 large spherical cells, each with a conspicuous 

 nucleus. Examine in the same manner the 

 cells from one of the sympathetic ganglia. 



h. The liver. 



Cut off a small piece of a fresh liver, tease 

 in a drop of salt solution, and look for the hepatic 



