164 



STRUCTURE OP MUSCLE. 

 Fig. 81.* 



to this view the cell membranes constitute the myolemma, and the 

 contents of the cell are a blastema out of which new cells are formed. 

 The disposition of these latter cells, in the production of fibrillae, is 

 probably much more simple than has hitherto been conceived. In 

 the muscular fibre of organic life the process would seem to stop 

 short of the formation of fibrillaa, the cells being accumulated with- 

 out apparent order. The corpuscles, observed by Mr. Bowman, in 

 fcetal muscle [fig. 79] and the nodosities of organic fibre are obviously 

 undeveloped cells and nuclei. 



Muscles are divided into two great classes, voluntary and involun- 

 tary, to which may be added as an intermediate and connecting link, 

 the muscle of the vascular system, the heart. 



The voluntary, or system of animal life, is developed from the ex- 

 ternal or serous layer of the germinal membrane, and comprehends the 

 whole of the muscles of the limbs and of the trunk. The involuntary 

 or organic system is developed from the internal or mucous layer, and 

 constitutes the thin muscular structure of the intestinal canal, bladder, 

 and internal organs of generation. At the commencement of the ali- 

 mentary canal in the oesophagus, and near its termination in the 

 rectum, the muscular coat is formed by a blending of the fibres of both 

 classes. The heart is developed from the middle, or vascular layer of 

 the germinal membrane ; and although involuntary in its action, is 



* A. A muscular fibre of animal life enclosed in its myolemma ; the trans- 

 verse and longitudinal striae are seen. 



B. An ultimate fibril of muscular fibre of animal life, according to Mr. Bow- 

 man. 



c. A muscular fibre of animal life, similar to A, but more highly magnified. 

 Its myolemma is so thin and transparent as to permit the ultimate fibrils to be 

 seen through. The true nature of the longitudinal striae is seen in this fibre, 

 as well as the mode of formation of the transverse striae. 



D. A muscular fibre of organic life from the urinary bladder, magnified 600 

 times, linear measure. Two of the nuclei are seen. 



E. A muscular fibre of organic life, from the stomach, magnified 600 times. 

 The diameter of this and of the preceding fibre, midway between the nuclei, 

 Was T7W faninch - 



