224- ELEMENTARY BIOLOGY. [XIII. 



a. The sciatic, nerve. 



a. Find it on the dorsal side of the thigh by sepa- 

 rating the biceps and semimembranosus mus- 

 cles ; it appears as a slender white cord. 



p. Dissect it out carefully in the middle of the 

 thigh, noting the branches it gives off to the 

 various muscles. * 



7. Follow it up to the abdominal cavity, cutting 

 away the muscles, lying between the ilium and 

 tirostyle, which cover it in. 



6. Follow it down towards the knee : a little way 

 above the joint it divides into two branches ; 

 one (posterior tibial) runs inside the large head 

 of the gastrocnemius muscle, the other (pero- 

 neal) between its two heads. 



b. The posterior tibial nerve. 



a. Note especially the branch which it gives off 

 opposite the knee-joint, and which, after run- 

 ning for some way along the deep surface of the 

 gastrocnemius, enters that muscle. 



/3. Follow the nerve down the leg : it runs along 

 the tibialis posticus muscle, giving off branches 

 here and there. 



7. Near the foot it turns to the back of the 

 ankle-joint and enters the plantar surface of 

 the foot, where it ends in a number of branches. 



c. The peroneal nerve. 



a. This runs down the leg close to the peroneus 

 muscle, giving off branches on its way. 



