This chapter examines that a relatively small proportion of human tuberculosis is caused by tubercle bacilli of the bovine type. It considers the extent of the disease in cattle and the frequency with which tubercle bacilli are found in milk and other dairy products. Tuberculous cattle might be a source of human tuberculosis by dust or spray infection from cattle suffering from lung disease; by the eating or handling of the flesh of tuberculous cattle; or by consuming milk or some milk-product derived from tuberculous cows. S. Martin in his experiments for the English Royal Commission frequently produced tuberculosis by inoculating or feeding animals with flesh from tuberculous cattle, in which no tubercle could be detected by his ocular tests. The flesh from tuberculous cattle is undoubtedly sometimes infective. The main tuberculous lesions in cattle are found in the organs, membranes, and glands; but seldom in the flesh or meat substance.