MUSCULAR SYSTEM 829 



those of the higher mammals, have certainly wandered a long way from 

 their embryologic origin. 



The names and location of muscles of the frog should be thoroughly 

 reviewed at this point. 



In the higher vertebrates the anterior spinalis differs from the frog 

 by being divided into several rectus capitis muscles which connect the 

 first vertebra with the skull. 



The longissimus dorsi group lie on each side of the vertebral spines 

 in the angle between spinous and transverse processes and extends from 

 the pelvis to the head. This group is made up of a longissimus dorsi 

 proper in the lumbar region, an ileo-costalis (inserted on the dorsal part 

 of the ribs), and a longissimus capitis along the side of the neck to the 

 temporal region of the skull. 



The muscles of the appendages are divided into intrinsic and extrin- 

 sic groups. The former have their origin in or on the appendicular skele- 

 ton itself, the latter have their origin on the trunk or axial skeleton 

 and their insertion on the girdle or base of the limb. Intrinsic muscles 

 therefore move parts of the limb ; extrinsic move the limb as a whole. 

 Muscles are often divided according to their action as already seen. Pro- 

 tractors draw a member forward ; retractors pull it back against the 

 body ; levators lift it, and depressors pull it down ; flexors bend a limb 

 or its parts ; extensors straighten it and rotators turn it upon its axis. 



Some of the more prominent muscles are as follows : 

 Levators : 



trapezius (for fore limb). 



levator scapulae (for fore limb). 



Depressors : 



pectoralis (for fore limb): 

 serratus anterior (for fore limb). 



Protractors : 



pectineus (for hind limb), 

 adductors (for hind limb). 

 sternocleidomastoid (for fore limb), 

 levator scapulae anterior (for fore limb). 



Retractors : 



pyriformis (for hind limb), 

 pectoralis minor (for fore limb), 

 latissimus dorsi (for fore limb). 



The pubofemoralis draws the hind limb toward the mid line while 

 the gluteus muscle acts as a retractor and elevator. 



THE VISCERAL MUSCLES. 



As already stated the gill-bearing vertebrates develop a special 

 svstem of muscles in connection with the visceral arches which are used 



