CHOREA. Ill 



cease during sleep ; in kind they resemble gesticu- 

 lations, and in their combinations and successions 

 are probably such as may occur during conditions 

 of health. Each movement probably depends upon 

 a discharge of motor force from some nerve-centre 

 corresponding. Chorea is dependent upon a brain 

 condition which we know only through the effect 

 produced upon the muscles by the brain. 



In children I have often observed that "the 

 weak and nervous " have much spontaneous finger- 

 twitching ; and I described this as one of the 

 physical signs seen in children who suffer from 

 recurrent headaches and associated pathological 

 conditions.* Such muscular unsteadiness seems 

 very analogous to the movement of young, grow- 

 ing, sensitive vegetables. 



The two tracings (Figs. 12, 13) indicate the con- 

 tinuous condition of spontaneous muscular un- 

 steadiness of the finger of a nervous child ; and 

 the continuous involuntary movement appears 

 analogous to that indicated by the tracing of the 

 movements of some plants. Now, if this analogy 

 between unstable mobile vegetable cells, and un- 

 stable nerve-cells, be legitimate, it should guide us 

 to further useful observations. 



To be brief, Darwin's observations show that 

 movement produced by the growth of vegetable 

 cells is constant in the leaves, stems, and roots of 

 many young plants.")" If the movement of nervous 



* British Medical Journal, December 6, 1879 ; see also " Brain," 

 1881, parts xi., xii., xiv. 

 t See the account given of circumnutation in plants, chap, ii. 



