192 HISTORY OF THE HUMAN BODY 



be the parietal or epimeric muscles, consisting of (i) the 

 axial, and (2) the appendicular musculature. This will be 

 followed by a short sketch of the visceral or hypomeric mus- 

 cles; and, lastly, the integumental muscles, a secondary sys- 

 tem, will be considered. 



The primary groups of skeletal muscles, with the exception 

 of the integumental, can be well shown in a condition ap- 

 proaching the primitive one by carefully removing the skin 

 from a salamander and inspecting the muscles as they lie in 

 their natural position (Fig. 52). In this preparation the 

 axial muscles form the bulk of the muscular system, and are 

 seen to consist of a series of muscle somites, or myotomes, 

 separated by thin perpendicular planes of connective tissue, 

 the myocommata. These axial muscles are divided by a 

 horizontal furrow, which runs along each side, into dorsal and 

 ventral masses, a distinction which is of fundamental impor- 

 tance, as these masses are innerved respectively from the dor- 

 sal and ventral branches of the spinal nerves. The groove 

 dividing them marks the place of the lateral line of fishes, 

 in which are located a row of specialized sense organs. The 

 axial muscles begin at the base of the skull and continue to the 

 end of the tail, but show some interruption of their course in 

 two places, corresponding to the attachments of the two pairs 

 of limbs. That of the anterior limbs, however, is seen to be 

 more superficial in character, and when the appendicular mus- 

 cles, that spread out in thin fan-like sheets over the trunk 

 myotomes, are removed, the myotomic muscles are displayed 

 in an almost uninterrupted sequence. In the case of the pos- 

 terior limbs, however, the skeletal girdle comes to lie imbedded 

 within the body muscles, and this, together with the cloaca, 

 causes a considerable hiatus in the sequence of the myotomes 

 on the ventral side, although dorsally the sequence is unbroken. 

 The muscles attached to the free limbs and their girdles form 

 the appendicular group, of little proportional importance here, 

 but destined in the higher vertebrates, with the development 

 of larger and more powerful limbs, to assume a far greater 

 bulk, and in some cases to even surpass that of the axial 



