1885.] of the Heart in Fishes, especially that of the Eel. 117 



of the muscular tissue from the effects of the preceding contraction. 

 If the shocks follow each other too rapidly, the curves obtained assume 

 the character of a descending series, resembling in the main a fatigue 

 trace of an ordinary voluntary frog-muscle — at least as far as the 

 progressive diminution in the size of the beats is concerned. When 

 the ventricle has thus been reduced to a condition of fatigue, if the 

 interval between the shocks be lengthened, the beats will for a time 

 show a progressive increase in force, as more time is now allowed for 

 the recovery of the tissue from the effects of contraction. Whenever 

 the recovery from the fatigued condition is complete, the beats remain 

 of fixed strength, showing no alteration whatever as long as the con- 

 ditions under which the experiment is conducted remain constant. 



Mechanical stimulation of the quiescent ventricle gives the same 

 results. 



Only in one ventricle (amongst a large number examined) have I 

 seen any trace of the " beneficial effect of contraction." And in that 

 case the ventricle had sustained considerable mechanical injury before 

 the experiment was begun. 



In order to test further the properties of the ventricular muscle 

 with regard to the production of a staircase of beats in response to a 

 regular series of stimulations, I have many times repeated the 

 experiment on a quiescent ventricle in the uninjured state filled with 

 normal blood. For this purpose the ventricle of a normally acting 

 heart was rendered quiescent by stimulation of the vagus nerve — a 

 proceeding which, by arresting the action of the other parts of the 

 heart, leads to ventricular standstill without (as will be explained in 

 the following pages) influencing in any way its contraction force. 

 The standstill of the ventricle occurs simply as a result of the 

 quiescence of the other parts of the heart from which the rhythmical 

 contractions are normally propagated to the ventricle. An uninjured 

 ventricle that has been rendered quiescent in this way is presumably 

 in a more normal state than an isolated ventricle artificially fed 

 outside the body. 



Such a ventricLe, excited at regular intervals by a series of 

 mechanical or electrical stimulations, gives a series of beats of 

 precisely equal strength, the commencing beats of the series being 

 maximal, and differing in no respect from the subsequent ones. 



With regard to the effects of faradisation upon the ventricular 

 tissue, some remarkable results are obtained. 



A surprising influence is found to be exerted by the rate of inter- 

 ruption in the faradising current. 



It is well known that in the case of ordinary voluntary muscle 

 when a slowly interrupted current is applied, the muscle contracts 

 at the rate at which the shocks are sent in. And when a more rapidly 

 interrupted current is employed, the muscle exhibits a more rapid 



