On the Latent Period of Muscle Contraction. 471 



longed latency with, an associated low, long curve, showing great 

 viscosity or slowness of extension, is to be observed. It differs in this 

 respect, however, that the lengthening of the latency is already well 

 marked after the muscle has been subjected once or twice to the 10" 

 tetanus. It is not unusual after a lengthening of the latency has 

 occurred for it again to diminish, if not to a point below the original, 

 at any rate to one distinctly below some of its predecessors. This 

 peculiarity does not persist to the point at which the viscosity of the 

 muscle becomes increased and the curve much prolonged, but coexists 

 with a strong contraction followed by complete relaxation, and this 

 point, be it coincidence or not, is worthy of note. 



The following figures show the frequent course of such an experi- 

 ment : — 



Length of Latency in D.V. = tIo"* 



Fresh 3-0 



After 10" tetanus 3'12 



20 

 30 

 40 

 50 

 60 

 70 

 80 

 90 

 100 

 110 

 120 



3-25 



33 



3-38 



312 



3-15 



3-50 



3-0?* 



3- 6 



4- 8 

 4-0 

 4-2 



120" tetanus administered in the course of about 30' at regular in- 

 tervals causes a prolongation of '00666". Fatigue is more rapidly 

 induced by indirect than by direct stimulation. 



Fatigue then increases the latency, at first slowly (500 induction 

 shocks or 60" tetanus), and then more rapidly till the exhaustion of 

 the muscle (1,500 single contractions or 130" tetanus) when a much 

 prolonged latency occurs. Near the commencement of stimulation a 

 temporary diminution of the latency is occasionally to be recognised. 



6. We have mentioned, at the commencement of this paper, that 

 Helmholtz, Wundt, and others regarded the strength of the shock as 

 playing an important role in modifying the length of latency, and we 

 also pointed out that this view had been opposed by Rosenthal and 

 Lautenbach. As the question appeared of importance, we directed 

 our attention to it, in the hope that we might be able to contribute 

 something to its elucidation. 



* The muscle was apparently contracting slightly when stimulation was delivered. 



