'Die Electrical Response of Muscle 2-il 



immediate shortenini^ of the time between each two periods of activity of 

 the heart. Even so slight an action as this, wliich does not affect the 

 respiration, may considerably reduce the pause between the next two 

 systoles, and within the next five seconds it may become half what it was 

 just before when the whole body was at rest. The quickening is not 

 maintained for long, so that in counting the pulse for one minute the 

 increased frequency is less striking. There is, of course, the same sudden 

 temporary quickening when other' muscles are put into action or when a 

 deep breath is drawn. 



IX. Note on the JMisuse of the Word "Rhythm." 

 I tried in my former paper (4) to avoid the use of this word for a suc- 

 cession of changes characterised by not recurring at regular intervals. I 

 still think it a misnomer to so apply it, but the word is so convenient, 

 and has been adopted by other people, e.g. Garten (6) and Piper (1), 

 regardless of any exception which might be taken to it, that I have 

 now myself applied it and its derivatives to phenomena which recur with 

 approximate, although not absolute, regularity. 



The working expenses involved in making all the experiments referred to 

 in this paper, with the exception of those made in 1902, have been defrayed 

 out of a grant from the Go\'ernment Grant Conunittee of the Roj'al Society. 



I have to thank Professor Bourne and Profes.sor Osier for providino- 

 me with the accommodation necessary for cai-rying on this and other 

 experimental work. 



Addexdu^i. 

 Since the above paper was written, another medical undergraduate has 

 enabled me to record the electrical response of his lower-arm flexors to a 

 series of artificial stimuli applied to the median nerve. It contrasts with 

 the response to the will in the same way as that to which fig. (> B refers 

 contrasts with that recorded in fig. 6 A, but the records are of exceptional 

 interest because the voluntary electrical efi'ect was exceptionally- strong 

 and regular, and the involuntary electrical ettect accordingly a great deal 

 stronger and more regular, although accompanied as before by a very much 

 smaller mechanical efi^ect. Records of the voluntary response show that 

 the electrical effects recurred at difierent times with frequencies of 100, 77, 

 .56, and 52 per second. In fig. 10 A, part of a record is reproduced which 

 exhibits chiefly a frequency of 56 per second. Fig. 10 B is the record of 

 the very next response of the same muscle (with the contacts in nowise 

 altered), not to the will, but to a series of 35 double induction shocks 

 succeeding one another at the rate of 50 per second — the secondary coil 

 being right up, but no core in the primary. The dynamometer was still in 

 the .same position in the hand, but while the voluntary eflbrt producing the 

 ('fleet recorded in A made the pointer move to 87, the strong artificial 

 excitation producing the efl'ect recorded in B made the pointer move only 



