_Distribution._ This affection was found in 1885 in the cantons of Berne, Lucerne and Argovi where it attacked 5 per cent. of the cattle and destroyed from 2 to 4 per cent. of those that suffered. It prevailed mainly in the summer (May to October) on the pastures, though not unknown at other seasons. Sucking calves were immune and the ages of a year to two and a half years were the main sufferers. _Causes._ Predisposing causes embrace such as induce weakness or debility, youth, low condition, cold intemperate weather, extreme heats, musty or spoilt fodders. The essential cause, the coccidium, appears to be taken in with food or water as sucking calves are largely exempt. The parasite is found in the gastric and intestinal epithelium of the diseased animals, in numbers proportionate to the severity of the attack, being very abundant when the disease is at its height, diminishing during convalescence, and disappearing entirely on recovery. Two species are found in this disease. =Coccidium Oviforme= is 40 to 50μ long by 22 to 28μ thick, ovoid, with a double outlined limiting membrane enclosing a refrangent protoplasm with a nucleus two or three times as large as that of an epithelial cell, and staining with hæmatoxylon or aniline colors. The young coccidia appear as round granular protoplasmic masses, without a capsule but provided with a nucleus. At first of a diameter of 9 to 10μ they increase to 26μ retaining the spherical form and acquiring the membrane of the mature parasite. As it grows the protoplasm separates from the wall and forms a globular nucleated mass, which after fifteen days divides into two and later into four masses or sporoblasts. Each sporoblast in its turn divides into two falciform corpuscles lying in contact but in an inverse sense to each other. Each of these under favorable conditions becomes a new amœboid individual capable of invading an epithelial cell and passing through the same stages of development as its predecessor. The coccidium oviforme is found in the epidermis in cutaneous psorospermosis of birds, and in the coccidian hepatitis in rabbits. =Coccidium Perforans.= In its mature form this is 25μ to 35μ long, by 14μ to 20μ broad. Its different stages of evolution are essentially the same as for the Coccidium Oviforme. It is a cause of intestinal Coccidiosis in both dog and rabbit as well as in cattle, usually killing the rabbit in from eight to ten days.