The Basis of Symptoms; The Principles of Clinical Pathology (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III INFECTION AND IMMUNITY ( With the Collaboration of Dr. E. Levy, Strassburg) In this chapter we purpose considering the various means by which the animal body resists the invasion of pathogenic microorganisms.1 The Portals of Entry.?How bacteria, under ordinary conditions, gain entrance to the body is still not definitely known. The body-surfaces are constantly beset by innumerable microorganisms, among them the ordinary agents of inflammation and suppuration: they are present on the skin, in the nose and mouth, in the trachea and gastro-intestinal tract, and in the vagina and urethra. Despite their intimate relation to the major part of those surfaces which lie between the organs and the outer world, they seldom gain access to the former; at least, according to our present conception, morbid processes are initiated with relative infrequency by bacteria which are normally present on these surfaces. It is evident, therefore, that some protective mechanism holds the organisms in check?this protective function, without doubt, residing in the cells which constitute these surfaces (see below); for the normal epithelium of the skin and of the respiratory and digestive tracts is able, as a rule, to prevent the invasion of micro-organisms. Solid particles other than bacteria encounter an equal difficulty. In the case of mercurial ointment, which seems to be an exception to this rule, soluble fatty-acid salts2 are no doubt formed on the skin in a manner analogous to the emulsification of fat before its absorption by the intestines. In view of the fact that leucocytes can pass between the epithelial cells, it is possible that they may carry back with them bacteria which they have taken up on the body-surfaces. Were this true, it would indeed be a marvellous proce...