THE MUSCLE-NERVE PREPARATION 23 



iliac attachment. Notice the twitch which occurs when the nerve, 

 which enters the under surface about its middle, is cut through. The 

 upper end of the muscle may be left attached to the ilium, or its bony 

 attachment may be cut away with it and the muscle thus completely 

 isolated. Its uppermost part contains no nerve fibres, and can be 

 used to show that, independently of nerve, muscle responds to all forms 

 of stimulation (electrical, mechanical, thermal, and osmotic). 



Iliac. 



Tensor fasc. lat. 



Triceps femoris (cruralis). 

 Add. magn. 



Ext. crur. brev. 



Tibialis ant. long. 



Tibialis ant. brev 



Tars. ant 



Add. magn. 

 Gracilis major. 



-,Gastrocnemius. 

 Tibialis posticus. 



Crural bone (tibia and fibula). 



Tendo Achillis. 



FIG. 29. Muscles of frog-leg ; ventral aspect (Gaupp). 



The gastrocnemius is generally used for experiments. Tie a thread 

 round its tendon (tendo Achillis), and cut this away from the 

 calcaneum. Holding it by the thread, tear the muscle upwards away 

 from the tibia, and sever this bone just below the knee. 



Next bring to view the sciatic nerve. Separate the muscles at 

 the back of the thigh by the aid of two pairs of forceps, keeping to the 

 medial of the two chief intermuscular septa, and the nerve will be seen, 

 accompanied by the femoral vessels. On no account touch the nerve, 

 but separate the muscles from it so as to expose it freely. 



If only a short piece of nerve is required, a wet thread may be tied 



