NECTURUS 5 



cucularis muscle, arising by two heads from the sides of the trunk, 

 behind the gills, and inserted, like the others, upon the humerus. 



Between the cucularis and the procoraco-humeralis is the 

 (8) omohyoid muscle. 



Separate these muscles at their origin and reflect them, 

 exposing deeper muscles beneath as follows: Beneath the 

 latissimus dorsi a rudimentary (9) serratus magnus, the fibres of 

 which, running longitudinally, are attached to the posterior 

 dorsal angle of the scapula. Beneath the cucularis (10) the 

 levator scapulae. 



Muscles of the Fore Limb. In the fore limb, besides other 

 muscles the following may be made out: (1) On the ventral 

 surface a narrow biceps muscle, extending from the proximal end 

 of the humerus to the anterior (radial) side of the forearm. 

 Behind this, also on the ventral surface, is the larger (2) coraco- 

 brachialis muscle arising from the coracoid cartilage and in- 

 serted on the distal end of the humerus. 



On the dorsal side is (3) the large triceps muscle which arises 

 by three heads, attached respectively to the coracoid, scapula, 

 and proximal end of the humerus, and is inserted on the ulna 

 (posterior side of the forearm) . 



In the forearm the muscles may be grouped in two divisions: 

 on the dorsal surface an extensor communis; on the ventral a 

 flexor communis. Both flexors and extensors can be resolved 

 into several components. 



Draw dorsal, lateral, and ventral views of the head and body 

 showing all the muscles. In the dorsal and ventral view put the 

 superficial muscles on one side of the median line, the deeper 

 muscles on the other. 



Muscles of the Trunk. In the trunk region the muscles of the 

 two sides are distinct from each other, and on either side they 

 are divided into dorsal and ventral portions by a lateral line. 

 The ventral portions are the more modified. In each portion 

 the muscles are subdivided by transverse non-muscular parti- 

 tions the myosepta or myocommata into separate myotomes 

 or myomeres. The dorsal myotomes constitute a longissimus 

 dorsi muscle on either side, while the ventral region is composed 

 of three layers of oblique muscles, external, middle, and internal, 

 the latter best seen from the ccelom. Make out the direction ot 

 the muscle-fibres in each layer. 



