=Lesions.= The lesions are represented by abnormal and irregular thickening around the interarticular cartilages. The cartilage is thickened, compressible, very spongy and without regular ossification. Diffused periostitis exists principally towards the extremities of the bone. Beneath the periosteum the surface of the bone appears rough and softened. On section the medullary canals are seen to be enlarged and filled with marrow of a gelatinous character. The Haversian canals are dilated, and the entire tissue appears very vascular. Chemical analysis proves that the mineral constituents of the bone, particularly the phosphates, have diminished by one-half; the organic constituents on the other hand are increased in a similar ratio, but the ossein is abnormal. Ossification has, in a word, been incomplete. =Diagnosis.= Diagnosis presents no difficulty except in the early stages before deformity has occurred. Rachitis can scarcely be mistaken for any other condition except perhaps infectious rheumatism, but the rapid course of the disease in the latter case, the persistence of fever and the swelling of the joint cavities sufficiently differentiate the conditions provided care is exercised. =Prognosis.= From an economic point of view the prognosis is very grave for if the lesions are extensive there is nothing to be gained by keeping the animal. =Treatment.= Treatment differs very little, whether the animals are still being suckled or have been weaned. In the former case it is necessary to improve the quality and chemical constitution of the mother’s milk by giving food, richer both in mineral salts and in nitrogenous material. Cooked grains, milk, and forage of good quality should be given freely. When the mothers are exhausted and anæmic it is better to feed the little animals artificially or to change them to a foster-mother. Those already weaned should be given good rich milk, eggs, boiled gruel, and drugs, such as the phospho-chlorate of lime, 1 to 1½ drachms per day (for a calf); lacto-phosphate of lime, 1 to 1½ drachms; bi-phosphate of lime, 1 drachm, or simply ordinary phosphate of lime. Oil containing 1 per cent. of dissolved phosphorus may be given in doses of 1 to 2½ drachms, according to the size of the calves, but its use calls for much care, and it should only be given for alternate periods of a fortnight. The glycerophosphates are not very active. Beef meal in doses of 6 drachms to 1½ ounces and chloride of ammonium in doses of 30 to 60 grains have also been used advantageously. The above drugs, but particularly the bi-phosphate of lime and chloride of ammonium, stimulate nutrition and diminish the quantity of phosphoric acid eliminated. OSSEOUS CACHEXIA.