1 2 2 THE INVOL UNTAR Y NER VO US S YSTEM 



excitation of the vagus fibres does bring about both inhibitory and 

 motor effects in the gut. It seems to me possible therefore to ex- 

 plain the myenteric reflex by the direct stimulation of the con- 

 nector fibres of the vagus ; but the connector neurons, of which these 

 fibres are the axons, are situated in the medulla oblongata and are 

 excited by sensory neurons in the central nervous system, so that 

 in the isolated intestine they could not be excited by any local sen- 

 sory neurons, if such existed. If then, as appears to be the case, 

 stimulation of the connector fibres of the vagus is an important 

 factor in this so-called reflex, such stimulation can only be brought 

 about by the direct excitation of such fibres, due to the bolus or 

 to the pinch, and not by any sensory neurons in the gut itself. 



Taking all these facts into consideration it seems to me very 

 advisable to suspend judgment upon the question whether or no 

 a true reflex takes place in a special enteric nervous system, until 

 the factors concerned have been much more carefully worked out 

 than has been done at the present time. 



