Structure of Smooth Muscle. 511 



The granular protoplasmic reticulum surrounding the nucleus is 

 quite variable in amount. In the two layers of the muscularis of the 

 small intestine it is restricted to a small mass at the pole of each 

 nucleus, Fig. Hi. In the muscularis mucosa} of the -small intestine 

 there is, surrounding the nucleus, a large spindle-shaped mass of 

 reticular protoplasm, connected by wide anastomoses with that sur- 

 rounding neighboring muscle nuclei, Fig. 14 a ; occasionally it is con- 

 nected by similar anastomoses with the stellate-shaped connective 



Text Fig. 2. 

 Eud to end anastomosis of smooth muscle cells. Intestine of pig. X ^^* 



tissue cells. Fig. 14 b. Fig. 17 shows a cross section through such 

 muscle tissue, in which the wide area of reticular protoplasm around 

 each nucleus is clearly indicated. 



In the muscularis of the intestine of the pig the main mass of 

 muscle consists of the myofibrillse. They are arranged in a heavy 

 layer around the nucleus. Fig. 16, and in heavy bundles connected 

 with adjacent nuclei. Fig. 15 a. In the muscularis mucosae there 



Text Fig. 3. 

 An isolated smooth nuiscle cell from the intestine of pig. X 650. 



i« often only a thin layer of myofibrillse around the margin of the 

 reticular protoplasm. Fig. 13, 14, 17. Between these two types 

 there exist all transitions. 



Fig. 7 shows a portion of a smooth muscle syncytium from the 

 intestine of Necturus. There is direct continuity between the 

 reticular protoplasm surrounding the nuclei as well as between the 

 myofibrillse. 



b. Smooth muscle with end to end anastomoses of fibers. 



