iv DIGESTION IN THE INTESTINE 251 



perceptible effect, either immediately or remotely, upon the move- 

 ments of the intestines. 



Peripheral stimulation of the vagi (after division of both 

 splanchnics, as recommended by van Braam-Houckgeest and 

 Jacobi, so as to remove the tonic inhibitory impulses passing along 

 these nerves to the intestines) constantly produces temporary 

 diminution or cessation of the intestinal contractions, owing to the 

 cardiac inhibition which causes intestinal anaemia. If the inhi- 

 bition of cardiac activity is prevented by intravenous injection of 

 atropine, peripheral excitation of either vagus has no effect on the 

 intestine. But if the stimulation is repeated several times an 



FIG. 86. Tracing of intestinal rhythm as in Pig. 85, during a later stimulation of right vagus. 

 (Bayliss and Starling.) In this tracing the primary inhibitory effect is scarcely visible, while 

 the subsequent motor effect is strongly marked, and at one point produces a tonic spasm 

 which obliterates the intestine and compresses the balloon. 



auguientor effect sets in, which increases with each stimulation. 

 The first effective stimulus is expressed in a temporary inhibition 

 which causes the dropping of one or two beats. In the succeed- 

 ing stimulations there is a double effect, i.e. the primary inhibition 

 is followed by an augmented rhythm ; the beats increase in 

 amplitude and frequency, and the relaxation is incomplete, so that 

 there is a great increase of muscular tone (Fig. 85). In many cases 

 the excitation is so pronounced that the lumen of the gut and 

 balloon are obliterated altogether by a strong tonic contraction 

 (Fig. 86). There seems to be no relation between the extent of the 

 inhibition and the amount of subsequent augmentation. 



Bayliss and Starling concluded that the vagus nerves contain 

 two sets of fibres, inhibitory and augmentor. The inhibitory fibres 



