1912.] " Narcosis Progression" in Mammals. 



157 



It sometimes occurs that, if the movements of narcosis progression have 

 occurred in a cat but have then ceased, the production of a state of asphyxia 

 may induce them again. They then appear some time after the commence- 

 ment of asphyxia at that point at whieh it might be expected that the beats 

 would be reaching their maximum extent. 



Recovery. — The asphyxia effect ends in the production of a state of 

 maintained flexion. If the' asphyxia be continued there may then be 

 no recovery of the movements of progression. But if the asphyxia be 

 terminated whenever the complete effect is attained — or, better still, a 

 few seconds before it is attained — the movements of progression again 

 make their appearance (fig. 6). Even when the asphyxia is stopped before 

 the attainment of the complete effect (that is, when the beats are still 

 present) the full effect is attained. The state of maintained flexion then 

 persists for a few seconds ; the beats reappear — being then of small extent 

 and rapid rate of rhythm ; become of greater extent and of slower rate ; 

 and finally again attain their normal appearance. The maintained flexion 



PROCRCSSIOM IN INDIV. MUSCLES 



Fig. 7. — Experiment C, LX, record 107 ; 14.7.11. — Normal cat, narcosis progression 

 registered in the isolated tibialis anticus and gastrocnemius muscles after motor 

 paralysis of all the other muscles of both hind limbs. The upper tracing is that of 

 the flexor (tibialis anticus), while the lower is that of the extensor (gastrocnemius). 

 Rise of the curve denotes contraction and fall denotes relaxation of a muscle. 



It will be observed that here the flexor beats are very well marked, but at this 

 period of the experiment are somewhat irregular in extent and in rate of rhythm. 

 No movement of gastrocnemius is registered. 



N 2 



