82 



Dr. W. R. Growers on the Automatic [Mar. 15, 



of air. But on some occasions curves were obtained of a different 

 form and shorter duration (fig. 5). The descent corresponded in 

 inclination with the ascent. The duration of each period in the rhythm 

 was nearly 9 seconds. It is to be noted that this is just double the 

 length of the spontaneous rhythmical variations in the case of the rise 

 after the mechanical stimulation by a cough &c. These more regular curves 

 would appear, then, from their curve and duration, to be the more direct 

 effect of the tendency on the part of the sphincter to rhythmical action 

 under the influence of the continuous stimulation*. 



The longest complete inhibition under a continuous injection of air 

 lasted 30 seconds. It is evident that this might easily have been mis- 

 taken for permanent relaxation. 



A comparison of these results with the action of the sphincter ani 

 under normal conditions corroborated the conclusion which Masius and 

 Groltz drew from their observation upon dogs, that the reflex action and 

 tendency to rhythmical variations is modified and controlled by the higher 

 encephalic centre. No variation in the uniform contraction of the 

 sphincter resulted from either the introduction of the instrument or from 

 its movement by a cough. Inhibition of contraction could, however, be 

 readily produced by an injection of air into the rectum. No initial rise 

 was observed under any circumstances : the inhibition continued during 

 the whole period of a short injection of air, and on the cessation of the 

 injection the pressure quickly rose to its original height. The duration 

 of the several parts of the action differed little from that observed in the 

 other cases. A latent period of 1*5 second was succeeded by a fall of 

 5 seconds' duration, a period of complete inhibition of 6 seconds, and a 

 subsequent rise which occupied 11 seconds. 



As far as could be ascertained, the internal sphincter was alone con- 

 cerned in this reflex action. The external sphincter appeared to be in 

 each Case relaxed. 



In the case of injury to the sacral nerves the direct communication 

 between the sphincter and the cord must have been interrupted ; the 

 reflex action, if from the cord, can only have taken place through the 

 sympathetic nerves. It is a point for future investigation, suggested by 

 certain points of resemblance between the reflex action of the sphincter 

 and that of the uterus, the intestine, and the heart, whether its action is 



* The immediate cause of the intermitting inhibition, no doubt, was in each case 

 the intermitting rectal stimulation ; but the greater uniformity of ascent and descent, 

 the resemblance in form of these causes to those which were undoubtedly spontaneous, 

 suggests that the tendency to rhythmical relaxation determined the time and form of 

 its occurrence in this case (fig. 5), whereas the longer curves, with steeper fall, 

 were determined more directly by the reflex inhibitory impressions. It is to be noted 

 that the latter often exhibited small secondary waves (as in fig. 6, a a), resembling the 

 spontaneous waves (fig. 3, e e) in their uniform curve ; while the regular waves (as in 

 fig. 4) never exhibited these smaller waves of ultimate rhythm, as they might be called. 



