1912.] 



" Narcosis Progression " in Mammals. 



141 



which occur in rabbits while subjected to the state of ether or chloroform 

 narcosis.* These movements are of interest in that they exactly resemble 

 the peculiar form of locomotion in that animal — simultaneous movements of 

 the hind limbs (" hopping ") and alternate movements of the fore limbs. 

 An additional point of interest is that scratching movements may occur also 

 in narcosis, and the phenomena of narcosis movements may slide, as it were, 

 from the one type into the other. 



In previous papers read before the Society, mention has been made of the 

 fact that similar movements (that is, of progression) may be induced under 

 narcosis in the guinea-pigf and in the cat * 



The movements in the guinea-pig are of interest because they do not 

 occur under normal conditions of ether or chloroform narcosis — at any rate, 

 they have not been observed in a long series of experiments, although some- 

 times after an operation and when the animal is recovering from the narcotic 

 it may make such movements. Under normal conditions the movements 

 which occur in the guinea-pig under narcosis are those of scratching — the 

 " narcosis scratch."§ 



In the cat scratching has not been seen by me to occur in narcosis 

 amongst about 200-300 individuals which I have observed in this state. 

 On the other hand, movements of progression occur with great frequence, 

 probably in about 50-75 per cent, of cats subjected to general chemical 

 narcosis induced by ether or chloroform or by a mixture of the two. 



In the cat the progression movements are best seen in the hind limbs, 

 where they may appear when the fore limbs exhibit no movement. They 

 exactly resemble the movements of progression in the normal animal. Some- 

 times the two hind limbs move simultaneously (or nearly simultaneously) in 

 the same direction, but more usually the narcosis progression is alternate. 

 It may rarely be confined to one of the hind limbs. 



The rhythmic phenomenon may be transient, when it appears then lasting 

 but a few seconds. In other cases it may last for long periods of time. 

 Eecords in which the movements have continued unchanged for several 

 minutes have been obtained. In such cases the narcosis must be kept at ;i 

 constant level. If the depth be increased the movements decline in extent 

 and finally die out. If the depth of narcosis be decreased the movement- 

 cease somewhat suddenly when in full strength. 



* 'Quart. Journ. Exper. Physiol.,' 1911, vol. 4, p. 151. 

 + 'Koy. Soc. Proc.,' 1912, B, vol. 84, p. 555. 

 { Ibid., 1912, B, voL 85, p. 278. 



§ 'Journ. Physiol.' ('Proc. Phys. Soc.'), 1909, vol. 38, p. 86; 'Quart. Journ. Exper. 

 Physiol.,' 1910, voL 3, p. 21 ; ibid., 1911, vol. 4, p. 19 ; ibid., 1911, vol. 4, p. 151. 



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