MORPHOGENESIS OF MUSCULAR SYSTEM 



711 



HYOID SWELLINGS 

 OF EXTERNAL E 



TRAPEZIUS 



DELTOID (CUT) 



LEVATOR SCAPULA 



AND 



SERRATUS ANTERIO 



LATISSIMUS OORSI 

 AND 

 TERES MAJOR 



EXTERNAL OBLIQU 



SACROSPl NA LI 

 tEPAXIAL MUSCULA 



RECTUS FEMO 



FIRST LUMBAR 



Fig. 328 — (Continued) Muscle development in the human embryo. (A and B redrawn 

 from Bardeen and Lewis, 1901, Am. J. Anat., 1.) (B) Differentiation of myotomal 

 derivatives in ll-mm. embryo. Observe that the dorsal division of the spinal nerves is 

 distributed to the epaxial musculature, while the lateral division of the ventral rami passes 

 to the intercostal areas. 



sclerotome, myotome, and dermatome (fig. 252). After the sclerotome has 

 departed toward the median plane, the myotome and dermatome reconstruct 

 the dermo-myotome which has a myocoelic cavity within (fig. 311A). The 

 inner layer or myotome gives origin to the muscle fibers of the later myotome. 

 The fate of the dermatome or cutis plate is not definite in all vertebrates. In 

 lower vertebrates it is probable that most of the dermatome gives origin to 

 dermal mesenchyme (Chap. 12). However, in mammals, according to Bardeen 

 ('00) in his studies relative to the pig and human, the dermatome or cutis 

 plate gives origin to muscle cells. On the other hand, Williams ('10) does 



