PRACTICAL PHYSIOLOGY. 



[xxix. 



a point, gently tear through the fascia covering the thigh muscles, 

 and with the blunt point of the finder separate the semi-mem- 

 branosus from the biceps, and in the interval between them observe 

 the sciatic nerve and the femoral vessels. Carefully isolate both, 

 beginning at the knee, where the nerve divides into two branches 

 the tibial and peroneal and work upwards (fig. 106). 



FIQ. 105. The Muscles of the Left Leg 

 of a Frog from behind, d. Coccy- 

 geo-iliacus; gl. Gluteus; p. Pyri- 

 formis; ra. Rectus anterior; ve. 

 Vastus externus ; tr. Triceps ; ri. 

 Rect. int. minor; sm. Semi-mem- 

 branosus; b. Biceps; g. Gastro- 

 cnemius ; ta. Tibialis anticus ; pe. 

 Peroneus. 



FIG. To6. Distribution of the Sciatic 

 Nerve (I.) of the Frog (see also fig. 

 105). st. Semitendinosus ; ad'". 

 Adductor magnus ; (II.) its tibial, 

 and (III.) peroneal divisions. 



The tibial branch passes over the knee-joint towards the middle line, and 

 enters the under surface of the gastrocnemius ; the peroneal branch passes 

 between the lateral tendinous origin of the gastrocnemius and the tendon of the 

 biceps, and then under the latter. 



(b.) Follow the nerve right upwards to its connection with the 

 vertebral column, and observe that it is necessary to divide the 



