Inasmuch as the lungs are the most common seat of tuberculosis, and infection occurs through the dissemination of the discharges of the morbid lesions, the sputum constitutes the most frequent medium of communication. It has been shown that the milk of tuberculous animals may assume this rôle, even when the mammary gland and the nipples are not the seat of the disease; and occasionally infected flesh used as food, and imperfectly cooked, may act in a similar way. Human beings, however, are considered the worst of fenders in this connection, by reason of the pernicious practice of promiscuous spitting, although it has been shown that tubercle bacilli may be contained in the fine particles ejected in the act of coughing. While the lower animals can not be charged with the offense of spitting, they do, however, cough; and it has, perhaps, not been sufficiently appreciated that in this way they