Definition. Susceptible animals. Causes: nervous lesions inconstant, youth, debility, anæmia, microbian toxins, cerebral embolism, rheumatism, trophic alterations in nerve cells, fright. Lesions: variable in seat and character, congestion of perforated space, corpus striatum, Sylvian convolutions, gray matter at root of posterior horn of spinal cord, etc., experiments of Chauveau and Wood. Symptoms: =dog=, local twitching, fore limb, one or both, neck, head, maxilla, eyelids, eyeballs, hind limbs, trunk, rhythmic, less when recumbent, usually absent in sheep, roused by excitement: =horse=, head neck, fore limb, trunk: =cattle=, head, neck, limbs: =swine=, hind limbs, neck, head: severe cases lead to exhaustion, emaciation, marasmus, paralysis. Duration: weeks, months, years. Treatment: laxative, tonic, hygienic, arsenic zinc sulphate, strychnia, sedative, belladonna, conium, cannabis Indica, chloral, acetanilid, trional, etc., icebags or ether spray to spine, cold douches, outdoor life. _Definition._ A neurosis characterized by constant twitching of muscles or of groups of muscles, and which usually ceases during sleep. _Animals Susceptible._ This disease is especially common in the dog, but has been recognized also in the horse, ox, cat and pig. _Causes._ Much difference of opinion exists as to the true cause of chorea. In many cases no nervous lesion has been found and therefore the disease has been pronounced purely functional. The victims are as a rule the young, weak and debilitated so that anæmia has been held to be the main causative factor. Then in dogs the affection is a common sequel of distemper and hence it has been attributed to toxic matters (microbian, etc.) in the blood. It should be added that European writers attribute the rhythmic spasms which follow distemper to eclampsia, epilepsy or tic, and claim that the contractions must be irregular or arhythmic in order to constitute chorea. English and American writers, however, have attributed less importance to this point and consider that the constancy 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 cribbiting is certainly not constant nor rhythmical nor is it a habit beyond the control of the will.