240 



PHYSIOLOGY 



CHAP. 



almost instantaneous arrest of the rhythmic movements, with 

 gradual decrease of muscular tonus. On removing the obstruction, 

 the viscus immediately gives a couple of beats, followed by a pause, 

 after which the rhythmic movements return in beats of growing 

 amplitude, while the volume of the intestine diminishes at the 

 same time, i.e. the tone of the muscles increases. This exagger- 

 ated return of intestinal activity is probably due to the great 

 vascular dilatation and hyperaemia of the viscus, consequent on 

 the prolonged anaemia which results from the occlusion of the 

 aorta. 



VII. The movements of the intestine, like those of the heart, 



CP 



FIG. 77. Effect on rhythmic (systolic and diastolic) movements of intestine, of obstructing the 

 dog's abdominal aorta. Recorded with balloon method. (Bayliss and Starling.) CP, carotid 

 pressure ; I, contractions of intestine. At 1 the aorta was blocked ; at ^ it was reopened. 



can be carried out independent of the central nervous system. 

 This is proved by the fact that they continue (in a constantly 

 peristaltic form) in excised loops of intestine, under favourable 

 conditions of temperature and moisture (Salvioli). The question 

 whether these movements are automatic or reflex, and whether 

 they depend on a rhythmic property inherent in the muscle cells, 

 or on the ganglia of Auerbach's plexus with which the muscular 

 coats of the intestine are richly provided, has not been completely 

 solved by the data we possess at present. 



The memoir published by Bayliss and Starling (1899) is of 

 great value in this connection. By an ingenious graphic method 

 they succeeded on dogs, anaesthetised principally with morphia, in 

 recording simultaneously the contractions of the circular coat and 

 the longitudinal coat of a loop of small intestine (exposed and 



