This disease is not only peculiar to the cow, but it may be said to be virtually confined to the improved and plethoric cow. It further occurs only at or near the time of calving. Indeed, these two factors, calving and plethora, may be set apart as preeminently the causes of this disease. It is the disease of cows that have been improved in the direction of early maturity, power of rapid fattening, or a heavy yield of milk, and hence it is characteristic of those having great appetites and extraordinary power of digestion. The heavy milking breeds are especially its victims, as in them the demand for the daily yield of 50 to 100 pounds of milk means even more than a daily increase of 2 to 3 pounds of body weight, mainly fat. The victims are not always fat when attacked, but they are cows having enormous powers of digestion, and which have been fed heavily at the time. Hence the stall-fed, city-dairy cow, and the farm cow on a rich clover pasture in June or July are especially subject. The condition of the blood globules in the suffering cow attests the extreme richness and density of the blood, yet this peculiarity appears to have entirely escaped the notice of veterinary writers. I have never examined the blood of a victim of this disease without finding the red-blood globules reduced to little more than one-half their usual size. Now, these globules expand or contract according to the density of the liquid in which they float. If we dilute the blood with water they will expand until they burst, whereas if solids, such as salt or albumin, are added they shrink to a large extent. Their small size, therefore, in parturition fever indicates the extreme richness of the blood, or, in other words, plethora. Confinement in the stall is an accessory cause, partly because stabled cattle are highly fed, partly because the air is hotter and fouler, and partly because there is no expenditure by exercise of the rich products of digestion. High temperature is conducive to the malady, though the extreme colds of winter are no protection against it. Heat, however, conduces to fever, and fever means lessened secretion, which means a plethoric state of the circulation. The heats of summer are, however, often only a coincidence of the real cause, the mature rich pastures, and especially the clover ones, being the greater. Electrical disturbances have an influence of a similar kind, disturbing the functions of the body and favoring sudden variations in the circulation. A succession of cases of the malady often accompany or precede a change of weather from dry to wet, from a low to a high barometric pressure. Costiveness, which is the usual concomitant of fever, may in a case of this kind become an accessory cause, the retention in the blood of what should have passed off by the bowels tending to increase the fullness of the blood vessels and the density of the blood.