Causes: inactivity, lowered muscular and nervous tone, twin pregnancy, approach of parturition, dry (clover hay) ration, concurrent diseases. Symptoms: moping, anorexia, depression, stupor, blindness, paresis, lethargy. Prevention: open air life, exercise, high muscular condition, avoidance of debilitating and relaxing conditions. Treatment: hygienic, nerve tonics, attend to concurrent diseases. Neurasthenia has been defined as an incompetency of the nervous system, leading to early fatigue, and inability to recuperate from the prostrate condition. Pending a better knowledge of the affection, I have given this name to an asthenic affection seen in pregnant ewes when nearing the completion of the period of gestation. _Causes._ In a large number of cases I have found several conditions so constant, not to say invariable, that they seem to deserve special attention in the list of causes: 1st. =Enforced inactivity.= In every instance that has come under my notice the ewes have been confined for several months to a barn or at most a confined yard so that exercise became impossible. The muscular system was flabby and soft, although as a rule there was abundance of fat, and the number of red globules did not vary much from the normal. In an animal that is naturally so active, and so accustomed to outdoor life the reduction of tone and vigor is to be expected. The same evil shows in other directions, thus after a snowy winter and close confinement the crop of lambs will sometimes perish of goitre without exception, while in subsequent years, with enforced exercise of the ewes, practically all escape. 2d. =Twin lambs= have been found in the womb of almost every case examined. The extra drain upon the system, and the depressing action of the load on an atonic ewe together with the symptomatic irritation are to be noted. 3d. The near approach of the =completion of gestation=, the cumulative effect of a long pregnancy, and perhaps the absorption of metabolic products from the fœtal membranes in course of preparation for detachment, and of leucomaines from the physiologically active or developing mammæ, doubtless have a prostrating influence on the susceptible nervous system. 4th. All had been fed on =clover hay= either as an exclusive diet or as part of their ration. This is sufficiently nutritive, as testified by the fat condition of the patients, but it may be that it was too nitrogenous for such an inactive life. Again the clover hay usually abounds in cryptogams and bacteria and their products, which may have contributed somewhat to the asthenia.