6 GUIDES FOR VERTEBRATE DISSECTION 



On either side of the mid-ventral line is a narrow rectus 

 abdominis muscle, each being continuous in front with the 

 pectoralis muscle, the two rectus muscles being separated by a 

 non-muscular linea alba. 



Draw a diagram of the trunk muscles sho\ving al T these points. 



Muscles of the Pelvic Girdle and Hind Limb. Extending from 

 the mid-ventral line to each hind limb are three muscles. In 

 front, arising from the anterior end of the pubis is (1) the pectineus 

 muscle, which is inserted on the proximal end of the femur. 

 Behind this, but also arising from the pubis, is (2) the pubo- 

 femoralis brevis muscle, inserted on the middle of the femur. 

 The posterior, (3) the gracilis muscle, arises from both pubis and 

 ischium and is inserted on the distal portion of the femur. 



Lift the gracilis and find beneath it the (4) adductor femoris 

 muscle with somewhat similar origin and insertion. 



On the anterior side of the thigh is (5) the rectus internus 

 muscle, arising from the anterior margin of the acetabulum and 

 inserted on the proximal end of the tibia. 



Behind this, on the ventral surface, is (6) the vastus internus, 

 also extending from the acetabulum to the tibia. Behind the 

 vastus internus is the distal end of the gracilis (3), already seen, 

 while on the posterior margin of the limb is a part of (7) the 

 femoro-caudalis muscle which arises from the pyriformis (see 

 below) and is inserted on the fibula. 



On the ventral surface of the shank are several muscles which 

 may be grouped as (8) a flexor communis. 



Dissect out the gelatinous tissue around and in front of the 

 anus and then make out, on either side, two superficial muscles 

 extending backwards to behind the vent. The more lateral is 

 (9) the pyriformis, the more medial, (10) the ileo-caudalis. 

 Trace each to its origin and insertion. Then lift the pyriformis 

 and find beneath it (i.e., dorsal) the rest of the femoro-caudalis 

 already seen. 



Draw a ventral view of these parts with the muscles found. 



In a dorsal view of the limb find the rectus internus, gracilis 

 and femoro-caudalis seen on the dorsal side. Just behind the 

 rectus internus is (11) the rectus externus, extending from the 

 ilium and terminating by a tendon on the tibia. Next behind is 

 (12) the glutaeus maximus, arising from the ilium and inserted 

 by tendon on the fibula. The semimembranosus muscle (13) 



