These and many other peculiarities of anatomy affect the pathological picture in birds. To be sure there are also noteworthy differences among the Mammalia, notably in the intestinal and genital tracts, but the pathologic response is not so varied as in the birds. When due allowance is made for the kind of stomach and absorptive area, apparent differences can be reconciled. For example, there is little confusion experienced in comparing acute erosive gastritis or the follicular enteritis of an omnivorous intestinal tract (man or pig), of a sacculated stomach and absorptive tract (the marsupial), of a carnivorous gut (cat) or a herbivorous compound stomach with its long digestive and water-absorbing surface (cow or camel) and an expansive muscular organ with a very extensive digestive area (seal). The type of lesion seems the same, in that inflammation, pus, necrosis, granulation tissue and cicatrices are comparable throughout the series. The size of the hind-gut has been taken by Metchnikoff as an indicator of the possibility of intoxication by degradation products of digestion. He believes that the capacious colon of herbivora and the short small one in carnivora explain the relatively greater life in the latter, because here less stagnation and absorption can take place. A reference to the expected lengths of life given before hardly substantiates this, and in our later chapters there will be found no strong indication that animals with large colons suffer with degenerative visceral changes more than those with small ones; nay even the reverse may be found true. In regard to epizoötics the behavior of man and lower animals is similar except perhaps that during an outbreak a smaller percentage of the latter give evidence of individual immunity and whole groups are apt to be carried off. Occasionally hygienic measures stay the ravages, at other times nothing seems to avail. Fortunately it is sometimes possible to sacrifice infective specimens and remove contagion. We have had few serious outbreaks, unless one might call our former heavy infection with tuberculosis in monkeys an epizoötic. The principal ones were an unexplained water fowl disease which carried off one hundred and forty- six birds, an imported epizoötic of quail disease which killed about the same number, a few cases of blackhead among wild turkeys, and a small group of cases of amœbic dysentery in monkeys and of thrush in passerine birds, and a small number of tuberculous pneumonias in snakes.