Transmission-time of Reflexes in Spinal Cord of Frocr 9 



taken before the severance (including the very iirst), but in none taken 

 after it, there is seen a much smaller, and again double, after-effect. This 

 indicates that when the nerve was intact, the muscle, as sampled by the 

 two spots connected with the electrometer, began to undergo the same sort 

 of disturbance in its electrical equilibrium as was the case previously m 

 response to the excitation of the motor nerve, but one smaller in amount, 

 and that this occurred 16 to 19 -So- after the first. In the particular 

 response to which the photograph here reproduced refers, it began 1 Do- 

 later. Its complete absence in the records taken after the severance of the 

 nerve from the cord makes the central origin of the stimulus which 

 immediately provoked it almost a certainty. 



What the effect, which I propose to call the second peripheral effect, 

 signifies, does not here directly concern us. I believe it to be in some way 

 dependent on the arrangement of the fibres in the gastrocnemius muscle, 

 and perhaps on the special spot to which the proximal electrode happened 

 to have been applied, since, with this muscle, which I had seldom used 

 before for electrical purposes, I have now come across it frequently in 

 response to strong stimuli, whereas I do not recall ever having seen it in 

 the thousands of records I have taken of the electrical response of sartorius 

 muscles to single break induction shocks, nor has it been present in any of 

 the few excised nerved preparations of sartorius muscles of these cooled 

 frogs which I have tried. I do not, however, wish to express a definite 

 opinion on this point, as I have not really investigated the matter, and the 

 occurrence of a succession of electrical changes resembling one another in 

 response to a single instantaneous stimulus in the sartorius muscles of frogs 

 suffering from drought^ suggests another interpretation. Whatever may 

 give rise to it is quite independent of the central nervous system, and 

 that is all we need know for our present purpose. The strength of the 

 stimulus required to produce it is sometimes less and sometimes more than 

 that required to produce a reflex eflect. 



I have • thought it superfluous for the chief object I had in view, to 

 deduce from the capillary electrometer records the curves indicating the 

 actual difterences of potential prevailing between the two spots of the 

 muscle led off from during each response. To anyone accustomed to 

 interpreting such records it is easy to find, without such deduction, the 

 place which indicates the coming into existence of a difterence of potential 

 of one particular sign, and thus to ascertain the time at which it occurs ; 

 also, if need be, to see where, and consequently when, its maximum is 

 reached, when it ceases to exist, or is reversed. To those who are not fully 

 conversant with the reading of such records, it may be of some assistance 

 to state here briefly that every rise on the photographic curve indicates a 

 movement of the meniscus which inscribes it towards the orifice of the 

 capillary — an adostial movement — and that such a movement, with the 

 1 See Durig, Arch. f. d. ges. Physiol., xcvii., p. 457, 1903. 



