150 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



insertion on the transverse processes of the vertebrae in contact with the origin 

 of the serratus ventralis. The mass in the neck is divisible into a medial 

 biventer cervicis and a lateral complexus. All of the epaxial muscles are very 

 complex consisting of numerous bundles. They are attached to various parts 

 of the vertebrae, ribs, and head, and have the general function of moving the 

 vertebral column and related parts. 



8. The muscles of the upper arm. Separate these muscles from each other 

 and identify them. 

 Rabbit: 



a) Triceps brachii. The triceps is the great muscle on the back of the upper 

 arm. It consists of three heads which are practically distinct muscles. Free 

 the heads. The long head is the large mass on the back of the upper arm; origin, 

 scapula, from the axillary border; insertion, olecranon. The lateral head is 

 on the lateral surface of the upper arm, ventral to the preceding; origin, greater 

 tuberosity of the humerus. The medial head is in contact with the humerus. To 

 see it spread the other two heads apart and look deep between them or cut through 

 the middle of the belly of the lateral head; origin, along the dorsal surface of 

 the humerus. All three heads insert on the olecranon and are the great extensors 

 of the forearm. 



6) Extensor antibrachii. On the medial surface of the long head of the tri- 

 ceps is a fascia from the lower part of which this muscle originates. Insertion, 

 olecranon; action, in common with the triceps. 



c) Biceps bracliii. On the anterior surface of the upper arm found by remov- 

 ing the insertions of the pectoral muscles is a spindle-shaped muscle, the 

 biceps. Origin, glenoid fossa; insertion, ulna and radius; action, flexor of the 

 forearm. 



d) Brachialis. This muscle is next lateral to the biceps and in contact with 

 the humerus. Origin, ventral and lateral surface of the humerus; insertion 

 and action, in common with the biceps. 



Cat: 



a) Triceps brachii. As above under rabbit with three heads. 



b) Extensor antibrachii. On the medial side of the long head, a thin sheet 

 of muscle, taking origin from the latissimus dorsi and inserted on the olecranon ; 

 action, in common with the triceps, tending also to rotate the ulna. 



c} Biceps brachii. As in the rabbit; visible only after cutting the insertions 

 of the pectoral muscles. Origin, glenoid fossa; insertion, radius; action, flexor 

 of the forearm. 



d) Brachialis. Lateral to the biceps, in contact with the lateral head of 

 the triceps. Origin, lateral surface of the humerus; insertion, ulna; action, with 

 the biceps. 



e) Anconeus. A small triangular muscle at the elbow joint, covered by 

 the distal end of the lateral head of the triceps, which should be deflected. 



