64 Veteriyiary Medicine. 



to constitute chorea. English and American writers, however, 

 have attributed less importance to this point and consider that 

 the constanc}'' and persistency of the contractions in the dog, 

 differentiate an affection from both eclampsia and epilepsy and 

 relate it rather to chorea. Tic as illustrated in crib-biting is cer- 

 tainly not constant nor rhythmical nor is it a habit beyond the 

 control of the will. 



Among other alleged causes of chorea is embolism of the ar- 

 teries of the brain or spinal cord. Angel Money went so far as 

 to inject a fluid containing arrowroot, starch granules and car- 

 mine into the carotids of animals, and produced movements 

 closel}' resembling those of chorea. Another theory connects 

 chorea with the rheumatic poison. Some English writers find 

 more than 80 per cent, of all cases in man associated in some wa}^ 

 with rheumatism, but in Philadelphia, Sinkler found that not more 

 than 15 per cent, showed such a relation. D. C. Wood as the 

 result of necropsies of a number of choreic dogs reached this 

 conclusion : ' ' Owing to emotional disturbance, sometimes stopping 

 of various vessels of the brain, or sometimes the presence of 

 organic disease, there is an altered condition of the ganglionic 

 cells throughout the nerve centres. If the cause is removed and 

 the altered condition of the nerve cells goes only so far, it re- 

 mains what we call a functional disease. If it goes so far that 

 the cells show alteration, we have an organic di.sea.se of the 

 nervous system." 



In man the element of sudden fright is awarded a high position 

 in the li.st of causes. 



Lesions. Constant morbid changes of structure have not been 

 established in chorea. On the contrary in the man}' careful ne- 

 cropsies of choreic subjects some lesion of brain or .spinal cord 

 has been almost always found. Dickinson always found con- 

 gestion of some part of the brain or spinal cord, but mo.st con- 

 stantly of the substantia perforata, the corpora striata and the 

 beginning of the Sylvian fissure. In the cord the cervical and 

 dorsal regions were the most commonly affected, and preeminently 

 the gray matter at the root of the posterior horn. The bilateral 

 symmetry of the contractions in cases of unilateral lesions, has 

 been held to discredit the theory of embolic origin, yet this may 



