IX.] PEOPERTIES OF CONTRACTILE TISSUE. 95 



nerves of the left side cat away the rest of the 

 tissue attached to it. Then lifting up the piece 

 of bone without stretching the nerves, cut 

 through with scissors the tissue attached to 

 them, follow the nerves on to the sciatic and cut- 

 through the tissue above and attached to the 

 sciatic including the branches given off by the 

 nerve ; isolate thus the sciatic down to the knee. 

 Letting the nerve rest on the muscles of the 

 thigh, cut through the skin of the upper part of 

 the thigh; seize the flap of skin with stout 

 forceps, and tear it away from the leg as far as 

 the foot. Placing the nerve on the muscle 

 below the knee cut away the muscles attached 

 to the lower half of the femur, and with a strong 

 pair of scissors cut through the middle of the 

 femur. Out through the lower (Achilles) tendon 

 of the gastrocnemius muscle close to its attach- 

 ment to the foot, and seizing the tendon with for- 

 ceps tear the gastrocnemius away from the other 

 muscles up to its attachment with the femur; 

 cut through the tibia and fibula just below the 

 femur. The preparation so obtained is called a 

 nenre-muscle preparation'. 

 Now pass a hook through the Achilles tendon, 

 clamp the femur, and taking up the preparation 



1 ■When two nerve-muscle preparations are to be obtained from one 

 frog, the lower part of the vertebral column should be bisected 

 longitudinally. It is perhaps somewhat better not to bleed the frog 

 before commencing the dissection, but in this case considerable skill 

 and patience are required to avoid cutting small vessels and so covering 

 the nerve with blood. 



