448 Mr. J. S. R. Russell. Circumstances under which [May 18, 



suspension of the administration of the anaesthetic when the spinal 

 cord has not been divided. 



2. The Effect of Bisection of the Spinal Cord vertically at the level of 

 the centres on whose activity the knee jerk depends. — These experiments 

 were undertaken to ascertain whether or no the centres to which the 

 knee jerks are related are separate and independent in their action on 

 the two sides, or whether the centre on one side is in any way related 

 to its fellow of the opposite side, and depending on its co-operation for 

 the proper performance of its functions. Since these experiments 

 were performed Dr. Sherrington has published the results of similar 

 experiments carried out by himself in connexion with the lumbar 

 cord of Macacus rhesus. My results entirely agree with his, and 

 showed that dividing the cord into two lateral halves, the incision 

 commencing at the level of the 1st lumbar roots and extending to 

 the level of the 1st sacral pair, had no appreciable effect, either in 

 increasing or diminishing the knee jerks. 



B. Circumstances under which the Alteration in the State of 

 the Knee Jerk is due to some Remote Cause. 



I. The Effect of the Removal of a Cerebral Hemisphere. 



Either hemisphere was selected, and during the process of exposing 

 it great care was taken to prevent the animal from losing more blood 

 than was absolutely unavoidable. When everything was ready for 

 the removal of the hemisphere the knee jerks were carefully tested, 

 so as to be certain that nothing had occurred to render them unequal 

 during the preparatory operation. The hemisphere was then excised 

 after the dura mater was dissected off it. The effect was immediate 

 and striking, the knee jerk on the opposite side of the body becoming 

 distinctly more active than that on the same side as that on which 

 the cerebral hemisphere was removed, this inequality being due to an 

 increased activity of the knee jerk on the opposite side, and not to a 

 diminished activity of that on the same side. 



II. The Immediate and Late Effects of Extirpation of Portions of the 



Cerebellum. 



1. The Immediate Effect of Extirpation of Portions of the Cerebellum. 

 — a. The removal of one lateral lobe was followed by great exaggera- 

 tion of the knee jerk on the same side, while that on the opposite side 

 was considerably diminished. So great was the exaltation of the 

 knee jerk on the same side as that on which the cerebellar lobe was 

 excised, that often a single tap on the patellar tendon sufficed to pro- 

 duce tonic extension of the limb. 



