CHAPTER I. THE SEATS OF LOCAL DISEASES. A PHYSIOLOGICAL OUTLINE. In the preceding four chapters we have studied the subject of human diseases as divided into those which are general and those which are local, and in the last two of these chapters we have taken a brief analytical review of the general diseases as a whole. To take into similar review the local diseases is our next task. For the purpose of this book it will be convenient to depart a little from the plan of the Royal College of Physicians in specifying the local affections, in order to condense the narrative and bring the facts of it into close compass. With this intent I shall place the local diseases under nine heads, corresponding to the systems of organs of the body;-the digestive, circulatory, respiratory, nervous, sensory, glandular and absorbent, muscular, osseous, and membranous. Let me, however, in a brief preliminary manner, first describe these systems. If we could by some sleight of science look physically through a living man and see how all his vital organs work, as we can look into the mechanism of a watch or a timepiece, we should discover in the nine grand systems of working organs, some active in their uses, some passive, but all playing important parts in the duties of maintaining or utilizing life. We should also discover them to be all bound together for a common object, that of bringing the various organs and systems of organs into one organic frame or whole; so that while each system and each organ is to some extent independent of the others, such intimate ties hold them all together, that it is difficult, if not impossible, for one alone to suffer and for the rest to be unaffected. THE DIGESTIVE SYSTEM. In the trunk of the body, we should first observe a tube which the ancients very correctly called the prima viæ, the first ways, and which we moderns call the digestive, or alimentary tube. The tube is truly the first way. It is the canal which receives the aliment out of which itself and the whole of the body is built up. It is the centre from which the body that is to be proceeds, in crude form it is true, but prepared for elaboration. Into this long canal, which, laid out and measured, would, in the adult, be found to be not less than thirty-two feet in length, and which is composed of many divisions, each playing, as we shall see, its own part in digestive work, the food and drink enter. Received here, the drink, if it be soluble, if it be water or a fluid miscible with water, is at once taken up by membranous and vascular absorption into the blood. The food, solid or semi-solid as it enters the mouth, is ground there or masticated, mixed with saliva which helps to fluidify its starchy and fatty parts, and is then swallowed into the stomach. In the stomach this food is digested and churned until its albuminous or flesh-forming structures are brought into solution, and this effected, the prepared fluid is passed into the first part of the intestine below the stomach, the duodenum, where, meeting with the secretions from the liver and pancreas, the bile and pancreatic juice, the starchy and fatty, or heat-producing, portions of it are emulsified, liquefied, and mnade ready also to be absorbed and further utilized. Thence the prepared nutriment, passing into a longer line of intestinal canal, the jejunum, and ileum, is further digested, and at last is, directly or indirectly, conveyed by two classes of vessels into the circulating blood, and through the blood into all other structures, to become for a time the veritable body of the man,-bone, muscle, sinew, nerve, eye, ear, heart, vessel, membrane,-everything there is of body. Finally, from that long absorbing portion of the alimentary tube sundry parts of the food that have been taken and are not wanted are passed into the large intestines, the cæcum, colon, and rectum,—with gases generated in the process of digestion, and débris of food that could not be digested or applied to the purposes of life. These are all passed on into the larger recepta cle of the intestine to be expelled, as the ejected results of the digestive process. In observing the parts of the digestive system we should note various structures and organs, beginning at the lips and extending to the lowest part of the intestinal tube. The canal is lined with the red mucous membrane which we see at the lips, and which, throughout its entire length, is surrounded by two layers of muscalar fibres, one longitudinal or long, the other circular. These are all enclosed, in some parts, in a strong investing sheath, the stomach and intestines being further invested, in great part, with a delicate serous membrane called the peritoneum. The parts of the alimentary system to be observed would be: —(a) the mouth, into which the saliva is poured,—the tongue, the fauces or back of the throat, the palate, the uvula and tonsils. (b) The pharynx, or dilated pouch at the back of the throat, ending in (c) the esophagus or gullet,-the tube extending from the pharynx to the stomach. (d) The stomach, or first true digesting receptacle, in which the albuminous or flesh-forming foods are transformed during primary digestion into chyme, which is passed through the pylorus, or exit gate of the stomach, into the duodenum. (e) The duodenum, or first portion of the small intestine, into which the liver pours its bile and the pancreas its emulsifying juice, and in which the fatty and starchy portions of the food are digested,-secondary digestion,-before being carried into the next small intestines. (f) The small intestines, jejunum and ileum, in which digestion is completed, and from which the prepared food is absorbed into the blood, partly by the veins,-direct absorption, and partly by the villi or absorbents which line the intestinal surface, and which convey the fluid to the glands of the mesentery, from whence, after elaboration, it may pass into the thoracic duct, and by that channel find its way into the veins, and so into the circulating blood. (g) The large intestine, called the colon, for receiving the débris, the undigested or useless part of food substances, and the gases arising from digestion. The colon springing from a pouch, the cæcum, situated at the end of the small intestine on the right side, first ascends, and then extending across the abdominal cavity from right to left, next descends, and at last terminates on the left side in the straight intestine. (h) The straight intestine, the rectum, with the ontlet of which the canal is terminated. () The peritoneum |