THE GASTROCNEMIUS PREPARATION 



17 



the vertebrae in the mid line into two symmetrical halves. Lift up 

 the muscles which have been cut from the urostyle, and turn them 

 outwards, so as to expose the sciatic, which can then be completely 

 isolated up to its three constituent cords, and so to the vertebrae. Cut 

 through the joint between the vertebrae and the ilium, and the vertebrae 

 can then be picked up, and by this means the nerve lifted and its 

 isolation completed down to the lower end of the femur, where it 

 divides into two branches. It is then laid on the gastrocnemius while 

 the muscles are separated from the femur, the triceps from the outer 

 side, and the adductors from the inner. The femur is then cut through at 



Fig. 22. — Leg Muscles of the Frog 

 seen from the inner slde. a, 

 Gracilis, s, Sartorius. v, Vastus 

 Lvi'ernus. g, Gastrocnemius. 



Fig. 23. — Leg Muscles of the Frog 

 seen from the Outer Side, t, 

 Triceps, b. Biceps. s»;, Semimem- 

 branosus, g, Gastrocnemius. 



about its upper third and the preparation is complete. Fig. 24 is a 

 drawing of such a nerve-muscle preparation, where f is the femur and 

 k the knee-joint ; g is the gastrocnemius and t the tendo Achillis with 

 its sesamoid bone s. The nerve n stili remains attached to a piece of 

 the vertebral column v, which serves as a convenient means of 

 handling the nerve. At n, is the branch of the nerve to the gastro- 

 cnemius. The femur can be clamped in the muscle forceps, and thus a 

 rigid support is given to its upper end. A fine thread is tied round 



c 



