less the liability to infection. 5. =Pre-existing Disease.=--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.