chap, ix.] STRIPED MUSCULAR TISSUE. 



73 



from other striped muscular fibres in the following 

 respects: (1) They possess no distinct sarcolemma. 



(2) Their muscle corpuscles are in the centre of the 

 fibres, and more numerous than in ordinary fibres. 



(3) They are very richly branched, each fibre giving off 

 all along its course short branches, or continually divid- 

 ing into smaller 



fibres and form- 

 ing a close net- 

 work (Fig. 43 A.) A 

 transverse section 

 through a bundle 

 of such fibres 

 shows, therefore, 

 their cross sections 

 irregular in shape 

 and size. (4) Each 

 nucleus of a muscle 

 corpuscle occupies 

 the centre of one 

 prismatic portion ; 

 each fibre and its 

 branches thus 

 appear composed 

 of a single row of 

 such prismatic 

 portions, and they 

 seem separated 

 from one another 

 ' at any rate in an 

 early stage by a septum of a transparent substance. 



93. Some muscular fibres are either markedly pale 

 or markedly red (Ranvier) ; in the former (e.g., 

 quadratus lumborum, or adductor magnus femoris 

 of rabbit) the transverse striation is more distinct 

 and the muscular corpuscles less numerous, than 

 in the latter (e.g., semi-tendinosus of rabbit, 



Fig. 43A. Striped Muscular Fibres of the 

 Heart. 



A, Showing the branching of the fibres and their 

 anastomosis in networks ; s, part of a thin fibre, 

 highly magnified, showing the moniliform 

 primitive fibrillse : c, one primitive fibrilla 

 more highly magnified. 



