465 



Immobility by the French authors, and which is described 

 in the following pages. 



CHOREA ST YITUS'S DANCE. 



A spasmodic twitching of certain muscles, occurring in- 

 cessantly except when an animal is sleeping, constitutes 

 chorea. Dr Todd has said that it is easier to say what 

 chorea is not, than to describe what its essential nature is. 

 " We may regard it as a disease dependent on a debilitated 

 state of the system, which does not in any way arise from 

 an inflammatory or hypersemic state of any part of the great 

 nervous centres or of other organs. Indeed, it is impossible 

 to fix upon any particular organ of the body in which any- 

 thing like structural lesion exists as a constant feature in 

 cases of chorea. The disease is one of functional disturb- 

 ance rather than of organic change, and this is borne out 

 by the results of post-mortem examinations ; for almost 

 without exception we fail to detect in those cases of chorea 

 which terminate fatally any morbid alteration which, phy- 

 siologically, could give rise to the phenomena ; and in the 

 great majority of cases, we find all the viscera in a per- 

 fectly healthy condition at least so far as we are enabled 

 to make out with the means at present at our command. 

 The structures which are obviously affected in chorea, are 

 the nerves and muscles. Doubtless a morbid state of both 

 exists ; but it seems most probable that the disturbed state 

 of the muscles is excited and maintained by a deranged 

 state of the nerves and nervous centres." 



Puppies are more liable to chorea than other animals. 

 It occurs in weakly dogs, and especially such as have been 

 prostrated by a severe attack of distemper. In many cases 

 it is restricted to a constant jerking of the lower jaw ; in 

 others there is very marked twitching of the frontal and 

 VOL. n. 4 A 



