SKELETAL MUSCLE 



119 



chymal cells, but Bardeen and WarrenLewis consider that " the myotomes 

 play no part whatever in the origin of the musculature of the limbs." 

 Moreover, Lewis states that " the idea that myotomes play a r61e in the 

 origin of the muscles of the head must be abandoned." A radical differ- 



D 



FIG. 108. TRANSVERSE SECTIONS THROUGH THE MIDDLE OF CERTAIN SOMITES IN SUCCESSIVELY OLDER 

 CHICK$EMBRYOS. A, B, AND C., THROUGH ONE OF THE SECOND PAIR OF SOMITES IN EMBRYOS OF 

 NINE, FIFTEEN, AND TWENTY-FIVE SEGMENTS RESPECTIVELY; D, THROUGH ONE OF THE FORTY-FOURTH 

 PAIR IN AN EMBRYO OF FIFTY-TWO SEGMENTS. X 230. (Williams.) 



ao., Aorta; d, dermatome; m, myotome; m. t., medullary tube; n, notochord; s, sclerotome; x, angle at which 



the myotome develops. 



ence in the source of smooth and striated fibers has therefore not been 

 demonstrated, but the two forms of muscle develop very differently. 

 The myoblasts which produce striated muscle are found in the midst 



