Transmission-time of Reflexes in Spinal Cord of Frocr 65 



7. In strychnine preparations, from which an effectual response can only 

 just be obtained when the nerve of the opposite limb is stimulated, the 

 cord delay is always roughly about double what it is when the nerve of the 

 same limb is stimulated. 



8. Whereas the delay in the case of the same-limb reflex is only some- 

 what shortened by the action of strychnine on the cord, the extra delay 

 in the case of the crossed reflex may be very considerably shortened by the 

 continued action of the drug, so long as its action is confined to the cord. 

 It may be reduced to half, or even to a fifth of what it was, in the course 

 of an experiment in which the drug was taking effect rapidly. It seems, 

 however, never to be reduced to less than 0-004 second, and seldom becomes 

 so short as this. It may vary in any one preparation independently of the 

 whole delay in the simpler reflex, but if the circulation has been affected by 

 the drug it also is long. 



9. The extra delay in the crossed reflex is no more affected by the 

 strength of the stimulus applied to the nerve than is the whole delay in 

 the same-limb reflex. It is affected, and in the same way, by changes in 

 the temperature of the cord. 



10. The cord delays in the uncrossed and in the crossed reflex are of the 

 same order when the excitability of the cord has been raised by phenol 

 instead of by strychnine, and bear the same sort of relation to one another, 

 provided that in the case of the crossed reflex the strength of the artificial 

 stimulus is not very greatly in excess of (not more than five times) the 

 strength just necessary to produce it. 



It has been inferred : — 



11. That in the same-limb reflex there is normall}' a single sj^napse 

 interposed in the conductive path of each individual fibre concerned, and 

 that the time taken to pass it in the normal animal probably lies between 

 0-010 and 0020 second. 



12. That in the crossed reflex investigated there are normally two 

 sjmapses interposed in the conductive path of each individual fibre con- 

 cerned, and that the time taken to pass the additional (" secondary " ) one is 

 about the same as that taken to pass the primary one in a normal animal, but 

 that it is subject to greater variation in each individual cord, and that there 

 is, determining it, something which is more susceptible to such agents as 

 drugs and fatigue. 



An abstract of this communication, under a somewhat different title, 

 appeared in the Proceedings of the Royal Society, B., vol. Ixxix., 1907, p. 503. 



VOL. I. — JAN. 1908. 



