PHYSIOLOGIC APPARATUS 



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the pelvic cavity, it passes down the thigh between the semi-membranosus 

 and the biceps muscles, in company with the femoral blood-vessels. Below 

 the knee it divides into the tibialis and peroneus nerves; the former sending 

 branches into the gastrocnemius. In its course, the sciatic sends branches 

 to the muscles of the entire leg. 



Carefully separate the biceps and semimembranosus by tearing the 

 connective tissue uniting them. The sciatic nerve and femoral blood- 

 vessels come into view; with a bent glass rod gently separate the nerve 

 from its surroundings from the knee to the thigh. Begin at the knee. In 

 order to expose the nerve at the pelvis, it will be necessary to divide. the 

 pyriformis and the ileo-coccygeus muscles. Care must here be exercised, 

 so as not to injure the nerve which lies immediately beneath. Lift up the 

 urostyle with the forceps and separate it from the last vertebra. With 



FIG. 352. LEG MUSCLES OF THE FROG. 

 VENTRAL SURFACE. (Eeker.) 



FIG. 353. LEG MUSCLES OF THE FROG. 

 DORSAL SURFACE. (Ecker.} 



the scissors cut off the vertebral column above the seventh vertebra. Place 

 the legs on the dorsal surface and then divide the seventh, eighth, and ninth 

 vertebrae lengthwise. With the forceps lift up one lateral half of the vertebrae 

 and free the nerve as far as the knee by dividing connective tissue and nerve 

 branches. Be careful not to injure the nerve with scissors or forceps. 



The Nerve-muscle Preparation. Divide the tendo-Achillis just below 

 its fibre-cartilaginous thickening at the heel, and detach the gastroc- 

 nemius up to the knee. Cut through the tibio-fibular bone just below 

 the knee-joint. Cut the femur transversely near its middle and remove 

 the muscles from the lower end, carefully avoiding injury to the nerve. 

 The completed preparation consists of the gastrocnemius muscle, the sci- 

 atic nerve, with half of the seventh, eighth, and ninth vertebrae and the lower 

 half of the femur. 



