148 



Mr. Graham Brown. 



[Nov. 12, 



other limb. Reappearance of the beats in the first limb then terminates 

 this pause ; but these beats are at first smaller than usual. The common 

 extent of the beats is soon attained. 



The duration of the long pause is approximately equivalent to that of so 

 many cycles. That is, it is approximately equal in duration to a simple 

 multiple of the duration of a single cycle when the two limbs are acting 

 together alternately. This correspondence is, however, only approximate ; 

 for minuter examination of the records reveals the fact that the pause is in 

 duration smaller than would be this simple multiple. The beats which 

 continue in being in the other limb become more rapid in rate of rhythm 

 than before. The change of rate of rhythm in such temporary unilateral 

 progression may be slight. It may change from 0'75 to - 9 cycle per 

 second only. In other cases it may change from 1*5 to 2*5 cycles per second. 



The beats of a limb in which the movements occur during the temporary 

 abolition of the beats in the other are often increased in extent as well as in 

 rate of rhythm. This increased extent may persist for a short time after the 

 resumption of movement by the other limb. It then gradually disappears 

 synchronously with the attainment by these beats of their normal extent. 



VI. Narcosis Progression in Cats : the Effect of some Lesions of the Nervous 



System. 



The movements of progression in the intact hind limbs may be recorded 

 — as they occur at the ankles — after certain lesions of the central and 

 peripheral nervous systems. 



Of these, the first which we may mention is that of decerebration by rapid 

 division of the brain stem through the anterior colliculi. 



In one experiment the movements of narcosis progression were recorded 

 before decerebration, and also 15 seconds after the infliction of the lesion. 

 Before decerebration the movements were very well marked, and were 

 alternate in the two hind limbs. After decerebration they were very much 

 reduced in extent, the reduction being greater in one limb than in the other. 

 The movements were synchronous in the two limbs at the beginning of the 

 record, but later they became alternate. The rate of rhythm also changed 

 after decerebration. Before it had been about 1*2 cycles per second. After- 

 wards it became about 2*6 cycles per second. The movements entirely 

 disappeared 40 seconds after decerebration. 



The movements of narcosis progression in the hind limbs may persist after 

 local injury to the lumbar region of the spinal cord. 



Thus, after the movements of normal narcosis progression have been 

 recorded, the lumbar spinal cord may be transected at the level of the entry 



