150 



Mr. Graham Brown. 



[Nov. 12, 



extensors of the other hind limb, but also the motor paralysis of all the 

 muscles (save the knee extensors) acting upon its own hip and knee joints. 

 The movements at this ankle still survived after transection of the lumbar 

 spinal cord at the level of the lower border of the Vllth post-thoracic 

 segment, and also after division at the lower border of the Vlth segment. 



Finally, I have lately divided the spinal cord in the lower thoracic region 

 very rapidly while the narcosis progression (in deep anaesthesia) was in being. 

 In this instance the movements were not recorded, but there appeared to be 

 little change in them. They ceased about 30 seconds after the lesion.* 



VII. Narcosis Progression in Cats : in Individual Muscles. 



When the individual antagonists at the ankle (tibialis anticus and 

 gastrocnemius) are prepared for the registration of their movements all the 

 muscles of the other hind limb are put out of action by motor paralysis, 

 while all the other muscles of the same hind limb are similarly paralysed. 

 After this drastic procedure it is not strange that the movements of progres- 

 sion narcosis are difficult to obtain — especially as they soon tend to disappear 

 in the normal cat as the narcosis is continued for any great length of time. 



The movements of progression narcosis have, however, been recorded in 

 the individual muscles, and in an experiment in which they were also 

 recorded in the intact hind limbs. 



In the intact hind limbs the movements were of good extent, regular, and 

 of a rate of about 1*6 cycles per second. They were recorded for a period 

 of about 90 seconds. 



After preparation of the individual muscles at the ankle the movements 

 persisted and were very well marked. The extensor — gastrocnemius — 

 throughout exhibited no trace of movement ; but the flexor — tibialis anticus — 

 presented a record composed of well marked beats, regular in extent and 

 rate of rhythm. These were composed of contraction phases immediately 

 succeeded at the summit of contraction by relaxation. The termination of 

 the phase of relaxation was succeeded by a pause in which the muscle 

 remained in relaxation, and then contraction again appeared (fig. 7). 



The rate of rhythm of these beats was about 1*5 cycles per second, so that 

 here the motor paralysis of one hind limb and the motor paralysis of all the 



* Note {added January 23, 1913). — I have lately repeated this result, with graphic 

 registration. The narcosis progression was occurring at a depth of anaesthesia so great 

 that rapid division of the lower thoracic spinal cord evoked scarce a movement. Again, 

 I have found narcosis progression to occur at a depth of anaesthesia at which reflex 

 movement at the ankle could hardly be elicited. To these recent observations I would 

 like to add a third : narcosis progression may persist through the procedure of decapita- 

 tion, and thereafter may suddenly merge, in one hind limb, into the scratch-reflex. 



