Transmission-time of Reflexes in Spinal Cord of Frog :i\ 



of the same side. In more than one excitable preparation, such a response 

 was obtained by merely removing the large resistance in the secondary 

 circuit of the current used to excite the nerve of the opposite side, or by 

 reducing it to one of not more than 10,000 ohms, if the secondary coil 

 were right up or nearly so. The difference of time in such response, 

 according as the nerve of the same side or that of the opposite side was 

 stimulated, is about that which would be taken for an impulse to traverse 

 between 30 to 45 extra mm. of nerve, and the only suggestion I can make 

 as to what happened when such abnormally strong exciting currents were 

 used is that these escaped to some nerve fibres in connection with the 

 motor cells, or nerve, of the opposite side. The same effect can be produced 

 not only by using abnormally strong induction currents, but also by making 

 something in or about the ventral part of the cord, according to Baglioni ^ 

 the motor cells, abnormally excitable, by the injection of phenol into the 

 circulation. In the two experiments I have as yet made with such phenol 

 preparations, records taken of responses to stimuli not quite but very 

 nearly strong enough to be felt on the tongue, applied to the sciatic nerve 

 of the opposite side, all showed, and in both preparations, besides the true 

 crossed-reflex effect (which I shall have to refer to immediately), an effect 

 occurring but Icr later than the direct effect as obtained by excitation of the 

 same-side sciatic. This had every appearance of being a direct effect itself, 

 and I cannot conceive that it was anything else, in spite of the fact thai it 

 was produced by stimulation of the nerve of the opposite side. When the 

 exciting current was weakened, the true crossed-reflex effect appeared as 

 before, and was equally strong, but it appeared alone. I have not, as yet, 

 further investigated the phenomenon, because it has seemed to me that all 

 the evidence obtained by the use of stinuili more nearly approaching, 

 though still exceeding in strength, the stimuli which must occur in nature, 

 goes to show that no physiological interest would be furthered by so doing. 

 That some morphological or even pathological interest would be served 

 thereby seems to me, on the other hand, to be not at all improbable, but it 

 is not with such interests that we are, for the moment, concerned. 



I think there can be no doubt that what Rosenthal- described as a 

 crossed-reflex contraction to be obtained only with very strong exciting 

 currents, and occurring at the same time as, or sometimes even before, what 

 he considers to be the same-side reflex (whether or not it was so), was 

 nothing but such a direct eflect due to the abnormal strength of the current. 

 There is nothing in Wundt's treatise to show that he ever obtained a 

 crossed-reflex contraction without the use of strychnine. The consideration 

 of the conclusion that he came to that the crossed-reflex time was only Aa 

 longer than that of the same-side reflex (" uncrossed," as we may now. if we 



' Baglioni, A. f. (Anat. u.), Pliysiol., 1900, Supplement. 



■^ Rosenthal, Abb. Berliner Akad., 1873, p. 104. The short mechanical latencies 

 observed by Francois Franck in what he considers to be the crossed reflex in the guinea- 

 pig, when very strong electrical stimuli were used, would fall, I believe, into the s;uue 

 category. 



