54 PHYSIOLOGY OF MUSCLE AND NERVE 



the body for a much longer time than those of warm-blooded animals. 

 It is a simple matter to reflect the skin from the leg of a pithed frog 

 and to isolate the gastrocnemius muscle by cutting through the tendo 

 Achillis and the fascia uniting it with the neighboring tibia. This bone 

 is then cut through directly below the knee-joint. Above the latter 

 is found the sciatic nerve which may be traced along the posterior 

 aspect of the thigh into the pelvis where its three roots are seen to arise 

 from the posterior end of the spinal cord. It should be divided at this 

 point and carefully separated all the way down to the muscle with 



Cruralis 

 Add. magn. 



Tib. ant. long. 



Tendo Achillis 



Fia. 25. MUSCLES OF HIND LEG OF FROG. (Ecker.) 



which it must of course be left in contact. The fibers of the gastroc- 

 nemius muscle are short and are arranged obliquely into a compact 

 mass of tissue. For this reason, the actual shortening of this muscle is 

 really quite inconsiderable in comparison with its power of contraction. 

 In the sartorius muscle, on the other hand, the fibers are long and are 

 placed more parallel to one another. This is also true of the gracilis 

 and semimembranosus muscles. Preparations of the latter give high 

 contractions, but the weight which they are able to lift is relatively 

 small. 



Methods of Registration. Myography. Soon after the experi- 

 ments of E. Weber (1846), pertaining to the elasticity of muscle, 



