THE RHYTHMIC AND PERISTALTIC MOVEMENTS 117 



the distance to which the inhibition extends after a single pinch 

 of the intestine. 



The known nervous factors in the small intestine which might 

 react to a stimulus are : 



1. The inhibitory fibres which enter in with the branches of 

 the superior mesenteric artery and arise from nerve cells in the 

 superior mesenteric ganglion, whose connector fibres are in the 

 splanchnic nerve. 



2. The connector fibres of the vagus nerve, which connect 

 with the motor nerve cells in the intestine, and by means of col- 

 laterals can affect a considerable area of intestinal muscle. 



3. The motor cells themselves and their motor fibres to the 

 musculature. 



If the stimulus which brings about the so-called myenteric 

 reflex affected at the same time I and 2, then the phenomenon 

 observed would be accounted for without invoking any reflex and 

 without the necessity of the supposition of a special enteric ner- 

 vous system differing in principle from that of the sympathetic 

 nervous system. The fact that the myenteric reflex does not 

 necessarily require a strong stimulus for its manifestation, but 

 can be produced by the presence of a bolus such as cotton wool 

 and vaseline, is not a fatal objection to this hypothesis, for it 

 is well known that distension of the lungs is alone sufficient to 

 stimulate vagus fibres from the lung alveoli to the respiratory 

 centre, so that local distension alone of the intestine may stimulate 

 fibres of the vagus and splanchnics in the same way. 



With respect to (i) Langley and Magnus investigated the 

 question whether the inhibitory fibres from the cells of the 

 superior mesenteric ganglion take any part in this so-called my- 

 enteric reflex, and they found that after removal of all the cells 

 of the solar ganglion and as far as possible removal of the mesen- 

 teric nerves, and after a length of time sufficient for degeneration 

 of all peripheral nerve fibres, the myenteric reflex was still de- 

 monstrable in the intestine. Evidently then, the reflex has 

 nothing to do with the sympathetic nerve fibres in the gut. The 

 phenomenon in question is therefore dependent solely on its 

 vagus system. 



In the case of the large intestine it would appear from the 

 work of Elliott and Barclay-Smith that the hardness of the bolus 

 plays an important part in bringing about the so-called myenteric 



