HISTOLOGY 



LITERATURE 



The histogenesis of striated muscle has been described by several writers, among 

 whom are Eycleshymer,. American Journal of Anatomy, 1902-1903, and M. Heidenhain, 

 Anat. Anz., 1901, and J. B. MacCallum, Johns Hopkins Hospital Bull., 1898. 



CARDIAC MUSCLE 



In considering this muscle as a class, we are departing from all for- 

 mer classification because several 

 kinds of muscle included in the 

 other classes are found in this. The 

 group, then, is a 

 physiological one, 

 not founded on any 

 common structural 

 distinction that we 

 can, as yet, pick out. 

 It is usually, how- 

 ever, different from 

 the other muscle tis- 

 sues of the body. 



The heart muscle 

 is distinguished 

 physiologically by 

 the fact that it must 

 keep constantly in 

 action at a con- 

 siderable rate of 

 speed and tension. 

 The consequent and 

 peculiar nervous 

 and gross arrange- 

 ments are a mor- 

 phological and a 

 physiological matter 

 rather than a histo- 

 logical one. Also, 

 as the heart is else- 

 where considered as 

 a part of the cir- 

 culatory channels, we shall pay attention here only to the cytology of its 

 muscle. 



ep. 



nfl 



FIG. 89. Portion of peripheral muscle tissue 

 from the embryo of a sucker, Catostomus. 

 Considerably more advanced than in Fig. 

 88. ep., single-layered epidermis; conn.t., 

 connective-tissue cells migrating from the 

 subcutaneous layer in between the myo- 

 tomes and thence in between the muscle 

 cells; bl.ca., blood capillary containing red- 

 blood cell and blood platelets; bl.c., blood 

 cell. From embryo of 10.5 mm. 



FIG. oo. Two 

 muscle cells from 

 the heart of Unio. 

 Blood cell 

 (wandering cell) 

 attached to one. 

 Xs8o. 



