A text-book of anatomy / edited by Frederic Henry Gerrish.

Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of anatomy / edited by Frederic Henry Gerrish. Source: Wellcome Collection.

    35/926 (page 31)
    or skin) which is capable of withdrawing decomposition-products from it, the particular poison which this organ can abstract is removed, and the blood is by just so much rendered less impure. Coming to another one of them, it gets rid of the foul material which can be unloaded at this door of exit; and so on at the others. The lungs are sewers for certain excrementitious substances, the kidneys for others, the skin for a third group, and the intestines for the remainder. In this way are eliminated all of the materials which result from the constant wearing out of the body. Org-ans Supplying Nourishment. If there were no compensation for the destructive changes which are going on incessantly, in a very short time every life would cease. But just in pro])or- tion to the extent of the waste, and ]:)ractically simultaneously with it, repair takes place. As an old particle lapses from a tissue a new one supplies its place without delay, even as the ranks of an army, though constantly suffering from the ravages of disease, death, and desertion, are kept full by the enrolment of fresh recruits. The portals of the body by which the new materials are intro- duced are the respiratory and the alimentary organs. First of all in importance is the respiratory system, which embraces the nasal passages, the pharynx, the larynx, the windpipe, the bronchi, the bronchial tubes, and the lungs, the last being the essential parts. But some critic observes immediately that the lungs have been mentioned already as channels of elimina- tion. Very true, but they are also channels of appropriation. Not only do they expel vile and injurious waste matters with eveiy outgoing breath, but they admit to the blood pure and sustaining nutrient material with every incoming breath. Here is one of the economies of nature—the wagon is never empty : it carries out the offal and it returns with a load of food. Second, we have the alimentary tube, with its attendant organs, the salivary glands, the pancreas, and the liver. This tube is very long, including the mouth, part of the pharynx, the gullet, the stomach, the small and the large intestines, the last mentioned having, like the lungs, the double and contrary functions of appropriation and excretion. It is furnished with apparatus by which solid food can be chopped, crushed, moistened, and reduced to a pulp, and other contrivances which dissolve and change the food in various ways until it is in such condition that it can pass through the walls of the tube and enter the capillary blood-vessels and lymph- vessels, which form fine networks in the substance of its walls. Passing into these two sets of vessels by tlie process of absorption, some of it reaches the blood immediately, and the remainder somewhat indirectly by way of the lymphatics. The blood, therefore, is seen to be enriched by gaseous material in the lungs and by liquids and liquefied solids in the alimentary tube. All of these additions are brought by the veins to the heart, and thence are pumped into the arteries. The latter pour their contents into the capillaries, which are embedded in the tissues. These minute vessels are so thin that the nutrient sub- stances in the blood can pass through their delicate wall, come into direct contact with the tissues, and flood them with food. To each tissue is offered a repast substantially identical with that furnished to every other, but no two of them choose the same articles from this sumptuous table, each having a selec- tive capacity for those things which are best adapted to the preservation of its own peculiar characteristics. So, each tissue having appropriated whatever it needs, the residue of the nutrient material is carried away by the lymphatics along with the waste products already mentioned. It will be observed that it is the vascular system which takes supplies to the tissues, and the same system which carries from them the products of waste. In connection with the alimentary tube were mentioned, as accessory parts, the salivary glands, the pancreas, and the liver. These are true glands—that is, organs which abstract certain materials from the blood, manufacture them into