1893.] Normal State of the Knee Jerk is altered. 455 



■when it is remembered that exaltation of the knee jerk precedes its 

 disappearance, for in no known method of producing shock of the 

 spinal cord is there an increased excitability of its centres before 

 their failure to act. It seems, therefore, more feasible to attribute 

 the whole of the result, as far as exaltation of the knee jerk is con- 

 cerned, to the absence of oxygen. 



V. The Action of Intravenous Injections of Absinthe and Strychnia. 



On the supposition that the former of these drugs acts mainly on 

 the cerebral cortex, and possibly in some degree on the bulbar 

 centres, but little, if at all, on the lower spinal centres, this drug 

 was given in doses sufficiently large to produce powerful generalised 

 convulsions, in order to test whether or no there is any evidence of 

 exhaustion of the lumbar centres after such discharges, when the 

 paths from these centres to the cerebrum, and from the cerebrum to 

 them, are left intact. It was found that, in spite of the most powerful 

 and oft-repeated generalised convulsions, there was increased action 

 rather than depression of the lumbar centres, as evinced by increase 

 of the knee jerk. That this was not a fair test of the condition of 

 the lumbar centres, as comparable to their condition when generalised 

 convulsions result from some condition which evokes discharge from 

 the higher centres alone, is proved by the results obtained with 

 absinthe, when the lumbar cord had been severed from its con- 

 nexion with the higher centres by complete transverse section of 

 the cord in the dorsal region. When this was done it was found 

 that, though no convulsions in those parts enervated from the spinal 

 cord below the level of the transverse lesion, yet there was abundant 

 evidence of a considerable direct action on the spinal centres, as 

 proved by the re-establishment of the knee jerk when its absence 

 probably depended on shock to the lumbar centres, and of its in- 

 creased action when it was comparatively normal before the adminis- 

 tration of the drug. That strychnia should cause increase of the 

 knee jerk, whether the spinal cord was intact or divided transversely 

 in the dorsal region, was only what was expected from the well- 

 known powerful action of the drug on the spinal cord. It is thus 

 clear that absinthe, like strychnia, has a direct action on the lumbar 

 centres, but that this action is very much less pronounced in the case 

 of the former than in that of the latter drug. 



VI. The Results of Section of the Spinal Cord. 



That complete transverse section of the spinal cord, sufficiently high 

 up not to interfere with the lumbar centres either by direct mutila- 

 tion, shock, or myelitic softening consequent on the lesion, does not 



