In enumerating the other causes of this disease we may refer to those noted above as inducing indigestion. As a primary consideration any condition which lowers the vitality or vigor of the calf must be accorded a prominent place among factors which, apart from contagion, contribute to start the disease de novo. Other things being equal, the strong, vigorous races are the least predisposed to the malady, and in this respect the compact form, the healthy coat, the clear eye, and the bold, active carriage are desirable. Even the color of the hair is not unimportant, as in the same herd I have found a far greater number of victims among the light colors (light yellow, light brown) than among those of a darker tint. This constitutional predisposition to indigestion and diarrhea is sometimes fostered by too close breeding, without taking due account of the maintenance of a robust constitution; hence animals that are very much inbred need to be especially observed and cared for unless their inherent vigor has been thoroughly attested. The surroundings of the calf are powerful influences. Calves kept indoors suffer to a greater extent than those running in the open air and having the invigorating influences of sunshine, pure air, and exercise; close, crowded, filthy, bad-smelling buildings are especially causative of the complaint. The presence in the air of carbon dioxid, the product of breathing, and of the fetid, gaseous products of decomposing dung and urine diminish by about one-fourth of their volume the life-giving oxygen and in the same ratio hinder the aeration of the blood and the maintenance of vigorous health. Worse than this, such fetid gases are usually direct poisons to the animal breathing them; for example, sulphureted hydrogen (hydrogen sulphid 2 SH_{2}) and various alkaloids (ptomaines) and toxins (neutral poisonous principles) produced in the filth fermentations. These lower the general health and stamina, impair digestion, and by leading to the accumulation in stomach and bowels of undigested materials they lay the foundation for offensive fermentations within these organs and consequent irritation, poisoning, and diarrhea. They further weaken the system so that it can no longer resist and overcome the trouble. The condition of the nursing cow and her milk is another potent cause of trouble. The feed of the cow is important. The influence of this is shown in the following tables: _Influence of feed on milk._ (_From Becquerel and Vernois._)