712 



THE MUSCULAR SYSTEM 



not tolerate this view, but believes, in the chick at least, that the dermatome 

 gives origin to dermal mesenchyme. 



The primitive position of the myotome is lateral to the nerve cord and 

 notochord. As development progresses, the individual myotomes grow ven- 

 trally toward the midventral line (fig. 327A). As this downgrowth progresses, 

 each myotome becomes separated into dorsal (epaxial) and ventral (hypaxial) 

 segments (fig. 328A). As indicated above and in figure 326D, the ribs grow 



MANDIBULAR SWE 

 EXTERNA 



HYOID SWELLING 

 EXTERNAL 



EXTERNAL AUD 

 MEATUS 



LATISSIMUS OORSI 

 EXTERNAL OBLIQUE 

 RECTUS ABDOMINIS 



SACROSPINALIS 



BENEATH 



LUMBO - DORSAL FASCIA 



SARTORIUS 

 QUADRICEPS FEMORIS 

 TENSOR FASCIAE LATA 

 GLUTEUS MEDIUS 

 BICEPS FEMORIS 

 GLUTEUS MAXIMUS 



20MM 

 /WEEKS 



UMBILICAL 



ARTERIES 



UMBILICAL VEIN 

 TIBIALIS ANTICUS 



___ EXTENSOR 

 -^ % H ALLUCIS 



LONGUS 



^», i-^d EXTENSOR 



\ia? ' DIGITORUM LONGUS 



Fig. 329. Later development of musculature in human embryo. (A after Bardeen and 

 Lewis, 1901. Am. J. Anat.. 1.) (A) Limb and superficial trunk musculature of 20-mm 

 human embryo. 



