Nearly one hundred species of microörganisms from the mouth have been studied and identified by W. D. Miller, who has clearly established that dental caries is due to the specific action of some of these parasites, which, gaining entrance into the dental tubules, determine fermentation and acid production, with erosion of the dental structure of the teeth and an increase in softening and destruction. In this way the teeth, as already indicated in Chapter IV, become paths of infection for germs which may travel but a short distance, causing only local disturbance, or which may be carried to other points about the head, producing disturbance in the antrum, in the neighboring bones, in the middle ear, and not infrequently in the brain. Abscess in the brain has been distinctly traced to caries of the teeth. Tuberculous infection is also common through this channel, and its most common expression is probably the invasion of the cervical lymphatics, superficial and deep, constituting those lymphatic tumors of the neck, formerly known as scrofulous, with their disastrous train of adhesions, suppuration, erosion, etc. SYPHILIS AND GONORRHEA. These are surgical affections whose secondary complications in the way of abscesses, infarcts, tumors, etc., have been dealt with in other parts of this work. It will be well to group all of these infections with anthrax, glanders, etc., into a class of infections which may be followed by tardy or late surgical sequels that may call for more or less radical operation. In the case of gonorrhea this is best seen, perhaps, in the so-called pus tubes of the female pelvis, which often require removal years after the date of the primary invasion. Endocarditis and pyemia are occasionally of solely gonorrheal origin, as well as peritonitis by extension from infected pelvic viscera. THE PUERPERAL STATE. This is seldom followed by surgical sequels, save in the instance of mechanical lacerations demanding plastic repair, or of septic infections, which, when life is saved, sometimes lead to disastrous consequences. Puerperal septicemia is in no respect different, pathologically speaking, from septicemia due to any other presumably streptococcus invasion; and the predilection which streptococci manifest for serous membranes, and especially joints, is well known. Consequently after puerperal fever one may meet with articular or peri-articular abscesses, affections of tendon sheaths, lymphatics, etc., or the complication may assume a different type, the veins and their contents being mainly involved, with thrombosis, infarct, etc., for its immediate results.