iv DIGESTION IN THE INTESTINE 243 



at which the first intestinal movements appeared, both in the 

 guinea-pig (26-27th day) and in man (77th day), is always later 

 than the appearance of nerve cells and nerve fibrils in the 

 muscular coat ; hence he upholds the neurogenic interpretation of 

 the intestinal movements. 



The peristaltic movements are true co-ordinated reflex acts, 

 which depend on the mechanical (and chemical ?) stimuli operating 

 in the intestine. They are propagated by the local nervous 

 mechanisms (Auerbach's plexus), independent of the central or 

 extra-intestinal nervous system. 



UP, 



FIG. 81. To show rate of propagated contractions. (Bayliss and Starling.) Two balloons 10 cm. 

 apart in a loop of intestine, cut at both ends. UB= upper and L.B= lower balloon. Time 

 marking 6 seconds. Rate of propagation 5 cm. per second, as shown by the delay in the 

 systoles 1, 2, 3, 4, 5, of the lower in respect of the upper tracing. (Ascending direction of 

 arrows shows direction of contraction.) 



According to Bayliss and Starling, "the production of the 

 true peristaltic wave is dependent on the unvarying response of 

 the intestinal nervous mechanism to local stimulation." They 

 formulated the law of the intestine (which might better be 

 termed " law of intestinal peristalsis ") as follows : " Local 

 stimulation of the gut produces excitation above and inhibition 

 below the excited spot." This confirms the observations of Colin 

 and van Braam-Houckgeest, from simple inspection, to the effect 

 that intestinal peristalsis always consists in a ring of constric- 

 tion preceded by a wave of relaxation, which forces the contents of 

 the viscus to pass along the intestine from above downwards. 

 Every point of the intestine is therefore subject to opposing 

 influences transmitted to it along its wall, viz. inhibitory impulses 



