6. =Personal Habits and Environment.=--_Diet_ has much to do with tissue resistance. Rats fed on bread are more susceptible to anthrax than those fed on meat. Hunger makes pigeons highly susceptible to the same disease, and artificial immunity induced in various animals is quickly destroyed by starvation. Prolonged thirst seems to have the same result. Excessive fatigue generally reduces immunity, as already mentioned. The various drugs which destroy red corpuscles impair immunity, and even by injection of water into the circulation the bactericidal power of the blood is reduced. White mice fed with phloridzin, which produces artificial diabetes, become highly susceptible to glanders, from which they are ordinarily exempt. In this connection may also be mentioned the various toxemias alluded to under the previous heading, which may proceed from the intestine, from the genito-urinary tract, and probably also from other sources. Climate has more or less to do, as also extremes of weather, with power to resist infection or to survive serious operations. Dark habitations, poorly ventilated, constitute surroundings which manifestly predispose to infection of all kinds. Rabbits inoculated with tuberculosis and confined within a dark cell, badly ventilated, become rapidly diseased, while others similarly inoculated, but allowed to roam at large, present but slight evidences of the affection. Certain occupations predispose to certain diseases. This is pre-eminently the case, for example, with workers in mother-of-pearl, who are exceedingly liable to a particular form of osteomyelitis; and with those who make phosphorus matches, who are prone to suffer from a peculiar necrosis of the lower jaw. Prolonged suppuration may produce such changes in the blood and tissues that vital processes of repair, cell resistance, and chemotaxis may be so far interfered with as to facilitate subsequent infection. Finally, the _influence of local injury to tissues_, particularly of contusions which cause tissues to lose their vitality, is strenuously insisted upon by all, and is spoken of repeatedly in other places in this work. Many tissues will succumb to inoculation after bruising, ligature _en masse_, etc., which before such injury are not in the least disturbed.