1877.] 



Action of the Sphincter Ani. 



81 



the degree of contraction. After an injection of air, as nearly instan- 

 taneous as could be, the latent period amounted on one occasion to 

 1*3 second. After a cough it varied from -8 to 1*2 second, the average 

 of five measurements being just 1 second. The latent period after the 

 introduction of the instrument, before the initial rise, varied from 1 to 

 1*5 second. 



The initial rise, when it occurred, was very uniform in its duration. 

 After the cough it varied from 1-1 to 1-5 second ; four out of six 

 measurements were exactly 1*5 second. After the introduction of the 

 instrument, the initial rise, in four measurements, lasted 1*3, 1*5, 1*5, 

 and 2 seconds respectively, the mean of the whole being very nearly 1*5 

 second. In the cases of disease of the cord the initial rise after the in- 

 troduction of the instrument was rather longer, lasting 2 seconds. 



The duration of the subsequent fall varied considerably. After the 

 introduction of the instrument it varied from 3 to 4*5 seconds, three out 

 of five observations being exactly 4 seconds. After a cough the fall 

 occupied from 3*5 to 5*5 seconds. The mean of all the measurements of 

 the fall caused by the mechanical stimulation of the instrument (on cough 

 and introduction) was 4*2 seconds. It was found that the more con- 

 siderable the fall the longer was its duration. Thus a slight fall caused 

 by traction on the instrument (not included in the above average) lasted 

 just 3 seconds. The initial rise did not exhibit this relation ; in the last 

 case it lasted 1*5 second, while the period of latent stimulation was 

 exactly 1 second. In the case of disease of the cord the duration of 

 the fall was 5 or 6 seconds. 



The subsequent rise always occupied a much longer period than the 

 preceding fall, varying in duration from 10 to 17 seconds. Only in one 

 instance was it less than 10 seconds, and in that the rise was imperfect 

 and was succeeded by a second fall. The mean of thirteen measurements 

 of the rise after all forms of stimulation, in the case of injury to the 

 nerves, was 13*5 seconds. In the case of disease of the cord it was some- 

 what longer, varying from 17 to 30 seconds. 



The rhythmical variations which in some cases occurred during the rise 

 (fig. 3) were from 4 to 4*5 seconds in duration, and, in the case of injury 

 to the sacral nerves, were very uniform. As there was no corresponding 

 variation in the stimulation, they "must be regarded as the expression 

 of a spontaneous rhythm in the action of the sphincter. 



The length of the rhythmical contractions which resulted from a con- 

 tinuous injection of air varied considerably, and, as already mentioned, 

 the form of the curves obtained also varied. Some (in each case) were 

 of considerable length, lasting from 12 to 17 seconds. In these the fall 

 was much steeper than the rise (figs. 4 and 6). These curves resembled 

 in this the curve which was obtained on any sudden stimulation, and 

 appeared to be merely a series of such curves, resulting from the inter- 

 mitting inhibition consequent on the alternate accumulation and escape 



VOL. XXVI. Gt 



