10 



PHYSIOLOGY. 



Ii now the heel cord be cut off below the heel there will remain such a 

 preparation as is represented in the accompanying figure, consisting of 

 the thigh bone with the calf muscle hanging from it, and the sciatic 



SHORTENED 



ELONGATED 



Fig. 3. Action of the Calf Muscle of the Frog, showing the Relations of the 

 Sciatic Nerve. 



Origin 



nerve still connected with the calf muscle. This may be supported by 

 holding the end of the thigh bone in a clamp on a retort stand. A 



light weight should be attached to 

 the heel cord. The muscle and 

 Bundle of Muscle Fibers nerve should be moistened with 

 water containing a little salt. On 

 pinching the free end of the nerve, 

 or cutting off the least bit with 

 scissors, the muscle will be made 

 to act. The shortening and thick- 

 ening will be plainly seen, and 

 by taking it between the thumb 

 and finger the hardening may be 

 felt. 



Structure of Muscle. 



Chipped beef shows well 

 the structure of muscle-. The 



'Muscle Sheath V 



CROSS SECTION 



Tendon 



Insertion 

 LONGITUDINAL SECTION 



Fig. 4. The Structure of Muscle. 



