40 



PRACTICAL PHYSIOLOGY 



the leg, which are cut away just below the knee (Figs. 32 and 33) . The 

 gastrocnemius muscle is protected from drying and from contact 

 with foreign substances by drawing down the " trouser " of skin. 



FIG. 33. 

 (Pembrey and Phillips.) 



FIG. 32. 



Diagrams of a muscle- and nerve-preparation. 

 FIG. 32. The first stage of dissection. 



FIG. 33. The second stage of dissection. The sciatic nerve exposed and the 

 gastrocnemius muscle covered by skin. 



(2) Lay the legs down with the dorsal aspect upwards. Raise 

 the urostyle in forceps, holding the lower end and cut up each 

 side. Cut it across at the base, talcing care not to cut the nerves 

 beside it. 



(3) Carefully divide the pelvis vertically in the middle line. 



(4) Divide the spinal column and any soft tissues remaining in 



3 1 c . J> > 



FIG. 34. Dissection of Sciatic Nerve. 



the middle line. Thus each pair of students receives one complete 

 half. (5) Dissect out the sciatic nerve from the spinal column to 

 the lower end of the thigh with a glass rod (Fig. 34). (6) Now 

 separate the muscle from the tibia and cut through the fascia of 

 the sole of the foot into which the gastrocnemius muscle is inserted, 

 leaving a good length of it. (7) Cut away all the thigh but the 

 lower end of the femur (Fig. 35, 1, 2, and 3), taking care not to 



