MUSCULAR TISSUE 



The early myoblast, of short spindle shape with central oval nucleus, 

 contains a granular cytoplasm, limited by a delicate membrane, the 

 sarcolemma. The granules may be called myochondria; whether identi- 

 cal with cytomicrosomes or with mitochondria, whether of cytoplasmic 



FIG. 98. SMOOTH MUSCLE CELLS FROM THE PIG'S STOMACH. 

 Isolated in equal parts of alcohol, glycerin, and water. Unstained. X 410. 



or of nuclear origin, are disputed points. No evidence of a distinct 

 spongioplasm is discernible. This observation tends to invalidate the 

 teaching of certain histologists, that the contractile fibrils (myofibrils) 

 represent modified spongioplasmic threads arranged in rectilinear meshes. 





FIG. 99. SMOOTH MUSCLE CELLS FROM THE WALL OF THE HUMAN INTESTINE. 

 Longitudinal section. Hematein and eosin. X 665. 



Moreover, it has been established by direct observation (McGill, et al.) 

 that the myofibrils arise through process of alignment and subsequent 

 fusion of the myochondria. McGill (Internat. Monatschr. Anat. u. Phys., 

 Bd. 24, 1907) recognizes two types of myofibrils, namely, stouter periph- 

 eral border fibrils (myoglia) which may pass beyond the limits of a 

 cell and form intercellular bridges; and the more central, or myofibrils 



