564 Mr. Graham Brown. Alleged Specific Instance of [Dec. 9, 



Guinea-pigs and rabbits when under the influence of a general anaesthetic 

 such as chloroform or ether exhibit peculiar scratching movements which 

 alternate from one hind limb to the other (fig. 2). 



The details of this phenomenon — which may be termed the "narcosis 

 scratch " — have been given at length in previous papers and need not here 

 be again repeated. But it may be said that suddenly a movement of 

 scratching appears in one hind limb, and that at the same time the back is 

 bent with its convexity to the opposite side, and the neck with its convexity 

 to the same side. The movements of the scratch last thus for a few seconds, 

 and then cease in that hind limb but appear in the opposite one. At the 

 same time the bendings of the back and neck reverse, so that the animal 

 assumes the mirror posture of that first described. In a similar manner the 

 scratching movements in this limb cease and reappear in the first hind limb. 

 And so the phenomenon proceeds, the alternation of scratching movements 

 from side to side of the body lasting for several minutes in some cases. If 

 the depth of anaesthesia be increased the movements decrease gradually in 

 extent and finally die away. But if the depth of anaesthesia be decreased 

 the movements cease suddenly. 



Becords of the movements obtained by the graphic method demonstrate 

 their likeness to the movements of a true scratch-reflex. A relative 

 difference lies in the rhythm of the component beats of the movement. In 

 the " narcosis scratch " the rhythm is slower than in the scratch-reflex. An 

 essential difference between them lies in the automatism and alternate 

 repetition of the scratching phases of the " narcosis scratch." In them there 

 is no ascertainable peripheral stimulus, and they continue automatically 

 passing from one hind limb to the other. 



(f) Phenomena in Decerebrate and in Decapitate Animals. — In the 

 decapitate cat, as Sherrington has noticed (49), the scratch-reflex may easily 

 be evoked by stimulation of the skin of the neck. 



In the same preparation, however, " spontaneous " scratching may some- 

 times occur. During the making of this preparation a ligature is passed 

 tightly round the neck of the carcase in order to prevent bleeding from 

 the veins. It is probable that the " spontaneous " scratching is due to a 

 mechanical stimulus set up by this ligature. 



It occasionally happens that similar " spontaneous " scratching move- 

 ments may continue for .a considerable time and not upon the one side 

 •of the body only. In these cases the scratch alternates from one hind 

 limb to the other, and the phenomenon — although its causation may 

 probably be traced to a peripheral stimulus — resembles very closely the 

 ■" narcosis scratch " in the guinea-pig. 



