THE RHYTHMIC AND PERISTALTIC MOVEMENTS 119 



noticed in the proximal colon. The caecum was the only de- 

 cidedly active part, yet even its activity was weak. Not once 

 was it seized by the deep blanching constrictions that occur in 

 the normal animal. Those seen were of slow and oscillatory de- 

 velopment, of shallow and irregular extent. The distal colon 

 had lost its pre-gangliomc (connector) constrictor fibres : the whole 

 its pre-ganglionic inhibitory and central sensory nerves. The 

 ganglia of the autonomic visceral nerves, and those of the 

 plexuses in the intestinal wall remained. They would not 

 atrophy, and indeed their activity might have been expected to 

 be the greater. Yet the movements observed under light ether 

 anaesthesia were utterly inco-ordinated and very weak." I con- 

 clude from these observations of Elliott and Barclay-Smith 

 that the co-ordination of movement, upon which the existence 

 of a myenteric reflex is based, is gone when the connector nerves 

 to the part have degenerated. 



My views on the nature of rhythm in involuntary muscle may 

 be summed up as follows : 



Involuntary muscle is covered over with a network of fibres, 

 which arise from peripheral nerve cells. This network degen- 

 erates when separated from its parent nerve cells. The nerve 

 cells belong to two nervous systems, the sympathetic and enteral 

 systems, and are called intrinsic or extrinsic according to their 

 situation upon the muscular organ or at a distance from it. The 

 intrinsic cells have been considered to be of a different character 

 to the extrinsic, and the initiation of rhythm in the involuntary 

 muscle has been ascribed to the intrinsic only. It was manifestly 

 impossible to ascribe it also to the extrinsic cells, for, being situ- 

 ated outside the rhythmical organ, they could be removed, and 

 yet the rhythm continued. The intrinsic cells to which the 

 rhythm is attributed, sometimes belong to the sympathetic system, 

 as in the ureter, sometimes to the enteral system, as in the in- 

 testine and heart, sometimes they are inhibitory cells, sometimes 

 motor. 



The evidence is strong, that isolated pieces of muscular tissue 

 will contract rhythmically in the absence of all nerve cells. 

 Such pieces of isolated muscles always possess a nervous network 

 round their muscle fibres, so that if the rhythm of the involuntary 

 muscle is always to be regarded as of nervous origin, the initiation 

 of rhythmic discharges must in this case be attributed to this 



