VOLUNTARY MUSCULAR FIBRE. 



139 



form dilatations, the object being, as he points out, to keep the 

 muscle supplied with oxygen during its long-continued con- 

 traction, which must interrupt the circulation. 



E. Meyer has since shown that Kanvier was over-hasty in 

 his generalization. What is true of the semitendinosus of the 

 rabbit is not necessarily true of other red muscles. 



The writer is able to confirm this statement. As to the dif- 

 ference between the semitendinosus and white muscle, he is in- 

 clined to admit the greater number of nuclei of the former, but 

 the difference in the stripes did not seem to him conclusive. 

 The peculiarity, however, of the minute blood-vessels of the 

 semitendinosus is very striking ; but in another red muscle of 

 the rabbit' s thigh he did not find the same arrangement. The 

 richness of the capillary network varies greatly in different 

 muscles of the same animal. Future investigations will, per- 

 haps, show that modifications in the arrangement of the minute 

 blood-vessels correspond with the 

 function of the muscle. 



The termination of muscle in ten- 

 don. This occurs in several ways. 

 Sometimes the fibre divides again and 

 again, ending in small bundles of 

 fibrillse which have lost all muscular 

 characteristics. Again, instead of 

 spreading out, a fibre may become 

 pointed, and the enveloping sarco- 

 lemma, reinforced with more or less 

 fibrous tissue, runs on as a delicate 

 tendon. Both these modes of end- 

 ing can be seen in the tongue. 1 The 

 cases in which a fibre loses its stria- 

 tion, and is apparently continued as 

 a tendon of about the same size, 

 present greater difficulties. By sep- 

 arating the fibres of a frog killed 

 by immersion in hot water, Ranvier has succeeded in demon- 

 strating that the sarcolemma incloses the tendinous end of the 

 fibre. The whole subject, however, of the ending of the fibres 

 is not exhausted. 



1 Thin sections of the hardened tongue of a small animal are to be recommended, 

 not only for the study of this point, but for that of striped muscle in general. 



FIG. 57. Anastomosing muscular 

 fibre of the heart, seen in a longitudinal 

 section. On the right, the limits of the 

 separate cells with their nuclei are ex- 

 hibited somewhat diagrammatically. 

 After Schweigger-Seidel. J. Arnold. 



