As stated in the last article, that form of inflammation of the udder which attacks the gland ducts and follicles, causing deep-seated, hard, nodular swellings, is often contagious. Franck has demonstrated this by injecting into the milk ducts in different cows (milking and dry) the pus from the bags of cows affected with mammitis, or the liquids of putrid flesh, or putrid blood, and in every case he produced acute inflammation of the gland tissue within twenty-four hours. He thinks that in ordinary conditions the septic germ gains access by propagating itself through the milk, filling the milk canal and oozing from the external orifice. He points to this as a reason why dry cows escape the malady, though mingling freely with the sufferers, and why such dry cows do not suffer from inflammation of the gland tissue when attacked with foot-and-mouth disease. In this last case it is evident that it is not simply the inoculation with the milker's hand that is lacking, for the skin of the bag is attacked, but not its secreting, glandular parts. Now that in any case of abscess we look for the cause in the chain forms of globular bacteria (_Streptococcus pyogenes_), in the cluster form of white, globular bacteria (_Staphylococcus pyogenes albus_), and in the golden and citron-yellow forms of clustered globular bacteria (_Staphylococcus pyogenes aureus_ and _Staphylococcus pyogenes citreus_), the formation of pus gives presumptive evidence of the action of one or more of these germs. So in cases of mortification of the bag; in the very occurrence there is fair circumstantial evidence of the presence of erysipelas micrococcus or other germ which kills the local tissues. Again, in tuberculosis affecting the bag (a not uncommon condition), the active local cause is without doubt the tubercle bacillus. It has been found that false membranes have formed in certain cases of mammitis in the cow, and Klein, after inoculating the diphtheria of man on the cow, found an ulcerous sore in the seat of inoculation and blisters on the teats and udder, in which he found what he believed to be the bacillus of diphtheria. The results are doubtful, even in the absence of false membranes. Lˆffler, too, in the diphtheria of calves, found that the germ was longer and more delicate than that of man, and that its pathogenesis for rodents was less, guinea pigs having only a nonfatal abscess. The presence of false membranes in one form of mammitis in cows does not necessarily imply its communicability to man.