1912.] 



" Narcosis Progression " in Mammals. 



149 



of the most caudal fibres of the Vlth post-thoracic posterior spinal root 

 without abolishing the narcosis progression. This lesion, if accompanied by 

 the destruction of the lower part of the cut cord, removes from the body the 

 centres for the extensors of the ankle joint, and leaves that for the flexors (or 

 part of it). Yet the movements at the two ankles may still persist. 



Again, in the same experiment, the remaining portion of the lumbar spinal 

 cord has been split in the middle line of the body in the Vlth, Vth, and 

 lower part of the IVth post-thoracic segments, and the left part of the cord 

 in these segments has been removed. Movements of narcosis progression 

 persisted in the right hind limb at the right ankle. They were very slight, 

 and it was almost impossible to register them, but palpation of the tendon of 

 tibialis anticus revealed the fact that that muscle continued rhythmically to 

 contract, and it appeared that the rate of the movements was about twice as 

 fast as before. 



The movements of progression in this experiment before the first lesion 

 (in the normal condition) had been of good extent and of a rate of about 

 0-95 cycle per second. After the first lesion the extent of the beats was 

 reduced, but their rate remained at about 1 cycle per second. After the 

 second lesion the extent of the beats was very markedly reduced, and the 

 rate of rhythm appeared to be about 2 cycles per second. At the time of 

 registration the beats appeared to be of a rate of about 1 cycle per second — 

 but possibly of about 1*3 cycles per second. 



Division of the posterior spinal roots of one of the two limbs in 

 another experiment was followed by abolition of the narcosis movements as 

 they occurred in that hind limb. The movements in the other limb 

 continued, but were slower than before. Only one experiment of this sort 

 has been successful. It is not usual for the movements of narcosis pro- 

 gression to last as long after the commencement of narcosis as is necessary 

 for the preparation of the spinal cord and roots before they are cut. It is, 

 perhaps, remarkable that the movements should survive the procedure in 

 any case. It is but fair to add that in this successful experiment the narcosis 

 progression had at the commencement of narcosis showed a marked tendency 

 to be unilateral in either hind limb, and especially in that the posterior 

 roots of which were not cut. 



In another case motor paralysis of one hind limb was produced by division 

 of all its spinal roots — both motor and afferent. In this instance the 

 movements of narcosis progression persisted in the other hind limb, but were 

 then more slow than before. 



In yet another experiment the movements of narcosis progression at one 

 ankle survived not only the motor paralysis of all the muscles save the knee 



