Friedberger and Fröhner found apoplexy quite frequent in sheep, ox. and dog, and rare in the horse, although more subject to the violent exertion which they put in the front of all causes. It is probable that the sluggish, pampered life of the first three animals, and the tendency to fatty degenerations and heart disease introduces a special predisposition as it does in man, while the horse, inured to an open air life and a vigorous muscular condition, is comparatively immune. Bright’s disease is a common cause in the human subject, with its resulting cardiac hypertrophy. The degenerations attendant on these conditions and especially fatty change (atheroma) in the walls of the cerebral arteries, pave the way for their rupture and for blood effusion. Emboli also carried from the diseased heart not only cut off the blood from the parts supplied by the plugged arteries, but increase the blood tension on the cardiac side of the obstruction and endanger rupture at any weak part. Thus they may cause apoplexy from anæmia without rupture or apoplexy from the pressure of effused blood. =Age= which is such a notorious factor in man is not without its influence in the lower animals. It is in the old that we mostly see disease of kidneys and heart and the degenerations of the tissues, including the brain and its vessels; in these, therefore, rupture and extravasation are the most frequent. The other causes are mostly connected with increased blood tension with or without a debility of the vascular walls. Violent exertions as in racing, coursing, dragging heavy loads up hill or on heavy ground, severe excitement, cerebral concussion, insolation, and intense congestion of the brain substance have all been recognized as causative factors. The compression of the jugulars by a small collar, the violent straining attendant on parturition, or constipation, and even the retrocession of blood from the surface when exposed to extreme cold, may contribute to the final rupture. In infectious diseases in which the toxic products tend to produce profound modifications in the blood and tissues, extravasations are met with in the brain as in other organs. Thus they are seen in anthrax, Texas fever, petechial fever, etc. Then the formation of =neoplasms= in the brain may be the occasion of the rupture of the vascular walls and apoplexy. =Hæmatoma= of the dura in the dog (Friedberger and Fröhner), =cholesteatomata= in the horse, and =carcinoma= may be apparent causes. The effect of =mechanical injury= must be admitted, as blows on the head, injuries from an ox yoke, and concussions during the battles of rams and bulls.