Transmission-time of" Reflexes in Spinal Cord of Frog 28 



the cord was normal). The records then taken with the muscle of the 

 opposite side when its nerve was stimulated (the first and the fourth of 

 which are reproduced in fig. 8, A and C, p. 51) show that the central 

 stimulus was then, a quarter of an hour later, producing as big an effect 

 in the muscle as the peripheral one, and also that the interval between the 

 arrivals of the two effects was shorter in all the responses, except the very 

 last, than it had been in the records taken before the administration of the 

 drug, the probable cord delay being 20cr or 19cr instead of the 28o-. 



Three other experiments [Nos. 16, 42, and 48 (the part of it referred to 

 on p. 13)], all made very soon after injecting the strychnine and when its 

 action was incipient, further lend some support to the view that strychnine, 

 so long as it is affecting the spinal cord alone, tends to somewhat shorten 

 the delay in it in the same-limb reflex, in so far as they all show that the 

 reflex time gets shorter as the time the drug has had to take effect becomes 

 longer. 



In four experiments [Nos. 8 (both sides in turn), 88, 46, and 54], all 

 made very soon after the administration of an extremely weak dose, one 

 would not have known from the records that any strychnine had been 

 administered at all : that is to say, the reflex effect was no stronger nor 

 longer than usually obtained from a normal cord. The probable cord 

 delay varied about 14cr in the first two, about 16o- in the third, and about 

 21a- in the fourth. There was one record obtained with the second muscle 

 in Exp. 8, in which the reflex response was slightly but decidedly stronger 

 than in the rest, and in this one it occurred 2o- sooner than in any of the 

 others. Moreover, the delay was lo- longer in the two responses which 

 showed a reflex effect with the first muscle in Exp. 8, than it was in an}' of 

 the four taken with the second. 



Taking all these facts into consideration, I think the conclusion is 

 warranted that strychnine, when it is producing no other effect than one 

 on the excitability of the cord, does not greatly alter the length of time 

 which elapses there in such a simple reflex as the one with which we have 

 hitherto been dealing, but that it does tend to reduce this time slightly, i.e. 

 by one- or two-thousandths of a second. Only when the heart also has 

 been affected by the drug is the time lengthened, owing to insufficiency in 

 the supply of oxygen to the cord or to some other consequence of defective 

 circulation, the impulses arising along the afferent nerve fibres taking then 

 a much longer time to be transmitted to their respective motor cells or else 

 the motor cells taking a longer time to react to their several impulses, some 

 perhaps taking longer than others. 



It was particularly when using weak stimuli to excite the dorsal roots, 

 stinuili too weak to have produced any ett'ect at all had the cord been 

 normal, that Wundt found the reflex mechanical latency in strychnine 

 preparations so very much prolonged, it becoming sometimes as much as 

 six or even ten times as long as in normal preparations. The variation of 

 latency with strength of stimulus appears indeed from his curves to become 



