MUSCULAR CONTRACTION 913 



Like the heart, smooth muscle is capable of setting up automatic con- 

 tractions of a rhythmic nature even when removed from the body. This 

 automatic rhythmicity is probably a fundamental property of the smooth 

 muscle cells, just as it is of heart muscle, for it has been shown by Gunn 

 and Underbill' 2 " in the case of intestinal muscle that it continues after 

 the nerve plexus which lies between the layers of muscle has been removed. 

 It is also to be seen in isolated smooth muscle cells grown in tissue cultures 

 in which nervous elements can be observed to be absent. 



