512 



Caroline ]\rcGill. 



As smooth muscle develops, in many places the wide side anas- 

 tomoses of the cells become less apparent, but the end to end union 

 still persists, text Fig. 2, Figs. 10, 11, 12. The loss of side anas- 

 tomoses is probably due to a rapid elongation of the central part of the 

 fiber between the anastomoses, thus pushing the anastomoses to the 

 ends of the fibers. It may possibly in places be due to an actual dis- 

 appearance of the anastomoses themselves. Much of the muscle of 



Fig. 4. A completely relaxed cell. 



Fig. 5. A cell coutractecl at one end. 



Fig. G. a cell contracted at each end. 



Fig. 7. A completely contracted cell. 



Text Figs. 4-7. 

 Muscle cells in various stages of contraction. Carotid of ox. X 650. 



the pig's intestine is in this condition. It occurs commonly in the 

 ip.uscle of the digestive and urino-genital tracts of dog, cat and man, 

 and was occasionally observed in the carotid of the ox. In this type 

 there may be continuity from cell to cell of the reticular protoplasm, 

 Fig. 13. Most often, however, only the myofibrillje form the anas- 

 tomoses, Fig. 11. The continuity of myofibrillse from fiber to fiber 

 was long ago described by Eouget, 1863, and has since been mentioned 

 by several writers. 



