100 REPORT \876. 



tbe contractions irreoiikr. Fiuall} the coutvaction« altogetliei- ceiise, Inil a vest .'f 

 liaif an hour or au hour restovos the irritability. ., , , 



The hj'pothesLS by ^vhich the author seeks to explain this artificial rhythm (a 

 rhythm which, in most cases, is (jiiite as regular as the heating- of a heart) is as 



follows:— . n- i. • 1 



Every time the tissue contracts it must, as a consequence, sutler a certain degi'ee 

 of exhaiistion, and therefore must become slightly less sensitive to stimulation than 

 it was before. After a time, however, tlie exhaustion will pass away, and the 

 original degree of sensitiveness will thereupon return. Now the intensity of the 

 faradaic sti'mulation, which is alone capable of producing rhythmic response, is 

 either minimal, or but slightly more than miaimal, in relation to the sensitiveness 

 of the tissue wlieu fresh." Consequently, when the degree of this sensitiveness is 

 somewhat lowered by temporary exhaustion, the intensity of the stimulation 

 becomes somewhat less than minimal in relation to this lower degree of sensitive- 

 ness. Tlie tissue therefore fails to perceive the presence of the stimulus, and con- 

 sequently fails to respond. But so soon as the exhaustion is_ completely recovered 

 from, .so soon will the tissue again perceive the presence of tlie stimulation._ It 

 will therefore again respond, again become temporarily exhausted, again fail to 

 perceive the presence of the stimulation, and therefore again become temporarily 

 quiescent. Now it is obvious that if this process occurs ouce, it may occur an 

 indefinite number of times ; and as the conditions of nutrition, as well as those of 

 stimulation, remain constant, it is manifest that the responses may thus become 

 periodic. 



In order to test this hypothesis the author nude the following experiments. 

 Having first noted the rate of the rhythm under faradaic stimulation of minimal 

 intensity, without shifting tlie electrodes or altering the streugth of the current, he 

 discarded tlie faradaic stimulation, and substituted for it single induction-shocks 

 thrown in with a key. He found tliat the maximum number of these single shocks 

 which lie could thus" tlirow in in a given time, so ns to procure a respome to every 

 shoch, corresponded exactly with the number of contractions which the tissue had 

 previouslv given during a similar interval of time when under the influence of the 

 faradaic current of similar intonsit)'. For instance, to take a specific case, it was 

 found that under the faradaic current the rate of the rhythm was one in two seconds. 

 Bv now tlirowing in single shocks of the same intensity, it was found that the 

 quickest rate at which these could be thrown in, so as to procure a response to 

 every shock, was one in two seconds. If thrown in at a slightly quicker rate, every 

 now' and then, at regular intervals, one of the shocks would fail to elicit a response. 

 The length of theselntervals, of course, depended on the rate at which the succes- 

 sive sliocks were thrown in ; so that, for instance, if they were thrown in at the 

 rate of one a second, the tissue wordd only, but always, respond to every alternate 



sliock. . . .,, ^ • K 



The foUowino-, and somewhat similar, experiment is still more conclusive. Aa 

 'alrerdy stated, the rate of the artificial rhythm under faradaic stimulation varies 

 v,-ith the strength of the faradaic current. Now, by choosing at random any 

 streugth of faradaic stimulation between the limits where rhythmic response oc- 

 curred, and by noting the rate of the rhythm under that strength, the author was 

 o-oneral!v able to predict the precise number of single induction-shocks lie could 

 afterwards aflxird to thro-.v i:i with the same strength of current, so as to procure n. 

 resijonse to every shock — this number, of course, corresponding exactly with tli;' 

 rate of the rhythm previouslv manifested under the faradaic stimulation. 



Other experiments, which'do not admit of being briefly detailed, have likewls.T 

 confirmed the above h-^-pothesis. Upon this hypothesis, therefore, the author ha ; 

 c-iustruetod a theory concerning the rhythmic action of organic tissues in general. 

 The details of this theory cannot be rendered in the present abstract; but in its 

 main outlines it is very simple, viz. that all such rhythmic action is due to the 

 alUn-uate process of exhaustion and recovery of cuntractile tissues, whicli has ju?t 

 been explained. Therefore the particidar case of rhythmic action of ganglionatod 

 tissues is supposed by this theory to bo due, not to any special resistance mechanism 

 on the part of the ganglionic tissues, but to the primary qualities of the contractile 

 tissue?. In i.>ther words, the functiou of the ganglia is supposed to l)e merely that of 



