1 1 o THE INVOL UNTAR Y NER VO US S YSTEM 



isolated piece of intestine suspended in Ringer's solution, and 

 showed that if a separation was made between the two layers of 

 muscle (longitudinal and circular) by means of a needle, so that 

 the slit-up piece of intestine was divided into two parts, one con- 

 taining the circular muscular layer, and the other the longitudinal 

 muscles, then spontaneous movements occurred only in the latter 

 half, while the circular musculature remained absolutely quiescent 

 and upon stimulation gave a local contraction at the place of 

 stimulation but no sign of any contraction wave. Upon micro- 

 scopic examination he found that the whole of Auerbach's plexus 

 was contained in the half containing the longitudinal muscles. 

 He agreed therefore with Bayliss and Starling that Auerbach's 

 plexus functioned as a central nervous system, in that impulses 

 reached it from the stimulated point and produced effects of op- 

 posite character, namely excitation of motor cells in the parts just 

 above the stimulus, and inhibition of those just below. Meissner's 

 plexus he found, took no part in the manifestation of this reflex. 

 This reflex has received the name of the myenteric reflex (Cannon). 



This evidence appears to differentiate the enteric nervous 

 system from the peripheral ganglia so characteristic of the sym- 

 pathetic nervous system, which, as already argued, represent 

 motor and inhibitory nerve cells of the involuntary nervous 

 system, which were once situated in the central nervous system. 



The evidence here seems rather to point to a complete 

 peripheral nervous system with a reflex mechanism of a de- 

 finite character, for the purpose of bringing about a necessary 

 co-ordinated movement for the onward propulsion of the food ; 

 and supports therefore the view of those who, like Bethe and 

 Nicolai, consider that in all organs containing unstriped muscle 

 fibres a network of nerve cells and nerve fibres is found in close 

 connexion with the muscles. This network represents, according 

 to them, the original diffuse nervous system, spread over all 

 contractile tissues, such as is seen in the swimming bell of the 

 Medusa, out of which in the course of evolution a concentrated 

 nervous system has arisen, except in the case of peripheral 

 organs which contain unstriped muscle, where this original system 

 still remains intact. 



The other view, to which I incline, is that there is no difference 

 between intrinsic or extrinsic nerve cells ; both are motor or in- 

 hibitory cells of the involuntary nervous system which have 



