A TOXIC NEPHROSIS IN CALVES TREATED WITH A DRUG CONTAINING TETRACYCLINE DEGRADATION PRODUCTS: Tetracyclines may prove to be toxic, especially when they are administered in excessive quantity. Toxicity and high mortality were experienced in calves that had been given the recommended dose of a drug which accidentally contained tetracycline degradation products, namely: 4-epianhydrotetracycline, epitetracycline and anhydrotetracycline. Lesions of acute and subacute nephrosis were observed. In calves dying rapidly, an abnormal coloration of skeletal muscles, myocardium and brain was also noted on postmortem examination, and a degeneration of the liver was evident. As the calves were already sick when they received the drug, dehydration and other pathogenic factors might have worsened their condition.