NORMAL SALINE. 147 



dissection of a frog already prepared, study the arrangement of 

 the muscles, as shown in Fig. 50. The skin of the frog is sup- 

 posed to be removed, and the frog placed on its belly, and the 

 muscles viewed from behind. On the outside of the thigh, the 

 triceps femoris (.r), composed of the rectus anterior (r.a), the 

 vastus externus (v.e), and the vastus internus, not seen from 

 behind. On the median side, the semi-membranosus (s.m), and 

 between the two the small narrow biceps (6). Notice, also, the 

 coccygeo-iliacus (c.i), the glutens (gl), the pyriformis (p), and the 

 rectus internus minor (r.i). 



In the leg, the gastrocnemius (g), with its tendo achillis, the 

 tibialis anticus (t.a), and the peroneus (pe). 



4. Make a Dissection. 



(a.) Remove the skin from the leg of a dead frog ; with a 

 blunt needle, called a " seeker " or a " finder," gently tear 

 through the fascia covering the thigh muscles, and with 

 the blunt point of the finder separate the semi-membranosus 

 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. 51). 



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

 the vertebral column, and observe that it is necessary to 

 divide the pyriformis (p) with small scissors, and also the 

 ilio-coccygeal muscle, when the three spinal nerves the 

 7th, 8th, and 9th which form the sciatic nerve, come into 

 view. 



5. Normal Saline. Dissolve 7'5 grammes of dried sodic chlo- 

 ride in 1000 cc. of distilled water. Tjiis is the best fluid to use 

 to moisten tissues. 



