BERMS IN TOE BODY. The question as to how germs enter the body and the means of defense against them which the body possesses is one of extreme importance. When we think of the om nipresence of germs. in the air we breathe, in the water we drink. in much of the food we eat, in the soil upon which we walk, in fact in or upon almost everything we touch or with which we come in contact• the question why bacteria do not oftener enter the body tissues would seem to be more rational than why they sometimes do so enter. Fortunately most germs are harm less; but many are capable of producing the most severe forms of disease. There are con stantly present in the month, nose, and upper air passages, as well as throughout the entire gastro intestinal canal, micro-organisms which, under ordinary conditions. are perfectly harmless. Then, too, the body is so built as to offer very powerful resistance to the entrance into it of most germ.. First in importance of the body defenses against germ invasion is the skin. The unbroken skin offers an almost impassable bar rier to the passage of most forms of germs. Being the most exposed, it is also the strongest of the body defenses against the entrance into it of micro-organisms. Few, if any, germs have the power to penetrate it, if healthy and intact. ..\ny person accustomed to dissecting, operating, or performing autopsies with ungloved hands, not ing with what impunity highly infectious ma terial may he handled provided there is no broken surface, and how serious are often the results of an overlooked wound or a chance scratch, realizes the importance of the skin as a protec tion against germs. There are, however, certain normal openings in the skin. These are: (a) those of the digestive tract—the mouth and anus, communicating with the (esophagus. stom ach, intestines. and rectum; (h) those of the respiratory tract, the mouth and nose—leading into the larynx, trachea, bronchi, and lungs; (el those of the genito-urinar• tract. the urethra and vagina—leading to the bladder, ureter, kidney, uterus. and Fallopian tubes: (d) the eye. These
openings and tracts are lined by mucous mem branes which may be considered as forming a second line of defense against germ invasion. Being less exposed than the skin, the mucous membranes are also less resistant than the skin to the entrance of germs. Indeed, to certain species of germs the mucous membranes are especially suseelitible; as the mucous membrane of the intestine to the bacillus 01 typhoid fever, that of the respiratory tract to the diphtheria bacillus and to the bacillus of pneumonia, and that of the genito-urinary tract to the gonococcus. To a great many of the most dangerous species of germs, however, the healthy mucous membrane, like the unbroken skin, presents an impassable line of defense. :Nor is the body helpless against the activities of germs even after they have entered its tissues. \\ hile the lymphatic system often furnishes the channels by of germs are carried from one part of the body to another, the lymphatic glands themselves un doubtedly act as filters arresting the progress of the germs, while the lymph-eells probably pos sess certain germ-destroying powers. Then, too, the white corpuscles of the blood are endowed with properties which enable them to take up germs and destroy them. It is largely for this purpose. in all probability, that the white blood-corpuscles leave the vessels and pass out into the surrounding tissues in inflammatory. conditions. Certain other cells probably possess this same power of destroying germs. such cells are known as phagocytes, and the process of germ destruction by them is called phugueytosis. There are also developed in the body during the prog ress of germ infections certain substances which appear to be in solution in the fluids of the blood. These substances are known as antitoxins (q.v.), and have a distinctly inhibitory effect on the further development Of the germs.