Cases of this kind have not been satisfactorily diagnosed, and as a rule domestic animals affected with partial paralysis are rarely allowed to live in a condition in which they are offensive to themselves and owners, a source of constant expense with little or no hope of recovery nor profit. Again, in the case of the large mammals, the prolonged recumbency and the low grade of nutrition in the semi-paralyzed parts, usually entail unhealthy sores and septic poisoning which sooner or later prove fatal. It is only, therefore, in the slighter cases, in which a fair measure of control over the limbs remains, that these cases are likely to survive. Trasbot suggests that many cases which pass for lumbar sprains are really chronic myelitis and on careful examination will show spinal sclerosis. _Causes._ These are largely speculative, yet doubtless the same causes which determine the acute form, will produce the chronic when acting with less force and greater persistency. The lesions that are left after an acute attack are calculated to keep up a measure of vascular and trophic disorder which will be found associated with more or less sclerosis. _Symptoms._ In Weber’s case in the horse (Recueil de Med. Vet., 1884, p. 432) the advance was slow, so that for nearly a year the manifestations were not diagnostic. At first there was weakness of the hind limbs when worked to fatigue. Perfect rest led to improvement, and work, to aggravation which became steadily worse and worse. For a length of time the horse maintained good condition, glossy skin, elevated head, alert expression, keen sight and hearing, and normal breathing and pulse. Standing in the stall there was no abnormal position of the limbs, nor evidence of lack of perfect control. But when moved all this was changed. He showed first lameness in the right fore limb and soon in all four members. The feet were swung and planted uncertainly, the animal swayed and staggered, the limb would knuckle over at the knee or fetlock, or bend at the hock, and be recovered with difficulty. After going slowly for a few steps he moved with greater freedom though still with difficulty, and the trouble was greatly aggravated when the eyes were blindfolded. Then every step threatened to precipitate him to the ground. The symptoms were essentially those of locomotor ataxy. The tactile sensibility was unimpaired, the loins had the normal sensibility, urination and defecation were natural and the appetite remained good. After ten months he showed loss of condition, dullness of the special senses, stupor, and a special sensitiveness about the head, and resented its handling.