—Here are reckoned, first, previous and long existent toxemias, e. g., syphilis, diabetes, scurvy, etc. Other conditions, like lithemia, cholemia, acetonemia, and the various conditions represented by oxaluria, or in which acetone, peptone, and excess of uric acid are found in the urine, also come under this head. One need never be surprised to find suppuration occurring in those cases in spite of due observance of all ordinary precautions, since by their existence immunity is destroyed and vulnerability increased. (See chapter on [Auto-infections].)
Recent toxemias also have important bearing in this same respect. For instance, after typhoid fever and other acute wasting diseases, including the exanthemas, surgical operations are sometimes followed by failure, and should always be postponed until complete recovery, except in cases of emergency. The condition to be hereafter described as enterosepsis, and which has previously been known under many different names, as fecal anemia, stercoremia, etc., is one which makes the performance of all operations dangerous, and which certainly predisposes to septic disturbances of all kinds. The postpuerperal state is also one in which operations are to be avoided if possible.
Certain anatomical changes peculiar to the various ages also belong in this category. Old age, with its accompanying arterial sclerosis, its cardiac debility, and other well-known tissue alterations, favors sluggishness of wound repair and leads not infrequently to sloughing or to bed-sores. Amyloid changes betoken impaired vitality. Children are much more liable to acute osteomyelitis than adults. Nursing infants are apparently exempt from many of the infectious diseases, but possess relatively small power of vital resistance to surgical operations. General anemia and impaired nutrition of the body predispose to most infections and to acute starvation.
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.
7. Fetal Infection.
—It is only in a very limited class of cases that infection can be transmitted from mother to fetus, but there are instances of this kind in which the surgeon is deeply concerned. As Welch has stated, syphilis is the only infection capable of direct transmission through the ovum or spermatozoön; but intra-uterine infection may occur in many ways, and many diseases may be thus transmitted. The placenta is usually regarded as a perfect filter; nevertheless, it is occasionally passable to microörganisms. These may be caused by preëxisting lesions in the placenta or by the virulence and activity of bacteria. It is known that in animals the bacilli of chicken cholera (inoculated into the mammalia), of symptomatic anthrax, and the pyogenic cocci, frequently traverse this barrier. In mankind infection in utero has been observed in smallpox, measles, scarlatina, relapsing fever, syphilis, tuberculosis, croupous pneumonia, typhoid fever, anthrax, and surgical sepsis.
SOURCES OF INFECTION.
That the effects of bacterial invasion may be anticipated and guarded against most effectually it is necessary that the practitioner should be thoroughly familiar with the sources from which they come, and the localities in and about the body which they most commonly inhabit or where they are met with in largest numbers.