Transmission-time of Reflexes in Spinal Cord of Frog 27 



impaired that synapse time is eventuall}' prolonged V)y insufficient strength 

 of stimulus, or it may be that the impairment has only emphasised some- 

 thing which does actually hold true for a normal, or more normal, animal, 

 but on a smaller scale, the difficulty in discovering it being in such greater 

 restriction of the threshold region. 



I would suggest therefore that in all responses in an}^ of my prepara- 

 tions the records of which showed that the maximal effect was not developed 

 until late, i.e. that the total central stimulus was not exerting its full force 

 at the beginning, there was want of accord in the time taken to pass the 

 several synapses, the greatest effect not being produced until all that can 

 be passed have been passed, and all the muscle fibres belonging to them 

 affected; and that this want of accord is brought about not by the 

 direct action of strychnine on the cord, but by its indirect action. 



The fact that, as a rule, when strychnine is affecting the cord only, the 

 effect at the recording spots after the administration of the drug is as 

 great, and becomes so in as short a time, as in the case of the direct re- 

 sponse, and that it is sometimes even greater than it (some of the responses 

 in Exps. 45, 47, 49 L, and 56 R), together with the fact that no increase 

 in the strength of the stimulus to the normal cord will make the reflex 

 effect larger than it otherwise is, seems to me, on the other hand, to indicate 

 that the smallness of the reflex response which is usual in a normal pre- 

 paration is not due to a smaller number of fibres being excited than by 

 the direct stimulus, but rather to the effect produced in each being smaller. 

 In this connection it should be mentioned that the reflex effect, as it is seen 

 in records taken with the normal cord, takes very nearl3^ if not exactly, 

 the same time to become maximal as the direct effect. 



The influence of altering the temperature of the back of the pre- 

 paration, and consequently of the cord, is well marked after the adminis- 

 tration of strychnine. This is shown by the experiment of which the 

 data are given on the following page. 



[T.\HLE. 



