64 



Anatomy of the Rabbit. 



ORIGIN. 



Voluntary muscle arises chiefly from the segmented areas or 

 myotomes of the embryo. The extent to which segmentation is 

 shown in the adult, however, depends for the most part on how far 

 the definitive muscle is removed from the vertebral 

 column or segmented portions of the skeleton. 

 The vertebral muscles themselves show throughout their attach- 

 ments to successive vertebrae the marks of segmental origin, but 

 many others, such as those of the abdomen, to a certain extent those 

 of the limbs, and those of the eye show practically no indications 

 of their segmental origin. 



While the bulk of voluntary muscle 

 is skeletal, part at least is related to the 

 skin. This forms a cutaneous sheet, 



DISTRIBUTION, divisible into the 

 cutaneus maximus 

 and platysma, commonly developed to a 

 considerable extent in mammals, but 

 reduced in man, and into the facial, 

 palpebral, and auricular muscles of the 

 head. The trunk musculature com- 

 prises a special group of cervical and 

 occipital muscles in relation to the neck 

 and head, and the general series which 

 are more nearly vertebral. The appen- 

 dicular muscles are distributed in 

 special groups connecting the limb as a 

 whole with the trunk and the various 

 segments of the limb with one another. 

 As already indicated the skeletons 

 of anterior and posterior limbs are considered to be equivalent part 

 for part. This is also true of the related muscles, but the respective 

 EQUIVALENCE positions of the segments of the limb in a 



OF LIMB MUSCLES, mammal are such that in examining the 

 muscles, it is important to determine the 

 equivalence of the bone surfaces. Since also certain conventional 

 ideas of flexion and extension prevail in human anatomy, it is 

 equally important to establish the corresponding relation as between 

 man and a quadrupedal form. The homologous surfaces may be 



Fig. 34. Arm muscles of rabbit 

 from the medial surface, illustrating 

 muscle action, flexion and extension. 

 b, biceps (flexor); tr, long head of 

 triceps (extensor); i, insertion; o, 

 origin; sc, scapula; h, humerus; 

 r, radius; u, ulna. 



