Copy 1, Volume 1

The study of medicine. Improved from the author's manuscripts, and by reference to the latest advances in physiology, pathology, and practice / [John Mason Good].

  • Good, John Mason, 1764-1827
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: The study of medicine. Improved from the author's manuscripts, and by reference to the latest advances in physiology, pathology, and practice / [John Mason Good]. Source: Wellcome Collection.

    65/784 (page 11)
    ance, and denominated chyle; in which state they are absorbed or drunk up by thousands and tens of thousands of little mouths of very minute vessels, which are sparingly if at all found in the stomach, but which abound upon the interior surface of the small intestines into which the stomach empties itself. These vessels constitute a distinct part of the lymphatic system. From the frequently milky appearance of their contents, they are known by the name of lacteals ; [but, as the chyle is not always white, perhaps a better name for them is chyliferous vessels.] They anastomose, or unite together gradually, and at length terminate in one or two common trunks, the chief of which is termed the thoracic duct, whose office is to convey the different streams thus collected from tke alimentary canal, as well as from other parts of the body, to the sanguiferous system, to be still farther operated upon by the action of the heart and lungs. | The saliva, or spittle, the fluid, with which the food is first blended in the mouth, is secreted by the salivary glands. Accord- ing to Berzelius, its solid contents do not exceed seven in 1000 parts, the rest being water. The principal saline ingredient in it appears, from Tiedemann and Gmelin’s analysis, to be muriate of potash ; but the sulphate, phosphate, acetate, carbonate, and sulpho- cyanate of potash are likewise present in small quantity. The human saliva contains but little soda. All physiologists, in their account of the uses of the saliva, represent it as lubricating the aliment preparatory to deglutition; as bringing sapid bodies under the influence of the organ of taste; and as softening the food for digestion. ; In the above sketch of digestion, the function of the lacteals or chyliferous vessels has been cursorily noticed. It must now be mentioned, that modern physiologists disagree about the extent of the office and pewer of these vessels. Thus, M. Magendie’s experiments lead him to doubt, in opposition to the statements of Hunter, whether they ever absorb any thing but chyle; and it is one of his doctrines, that all other substances, and particularly drinks, are conveyed from the alimentary canal into the circulation by the veins. It is the villi of the intestines, he observes, formed in part by the origins of the veins, which absorb all the liquids in the small intestines, except the chyle. From the commencement of absorption until its conclusion, the properties of those liquids are discoverable in the blood of the branches of the vena porte, but not in the lymph, or chyle, till long after absorption has begun. Magendie’s experiments also tend to prove, that they then reach the thoracic duct, not through the chyliferous vessels, but by the communication of the arteries with the lymphatics. The vena porte, which is the trunk of all the veins of the digestive organs, divides and subdivides in the tissue of the liver. Now, certain other experiments, of which M. Magendie gives the particulars, induce him to conclude, that this arrangement in the human economy has the effect of mixing the matter, absorbed in the intestinal canal by the veins, intimately with the blood; and that, if large quantities of drink and other substances, not chyle, were to be at once transmitted to the source of the circulation by the thoracic duct, without having undergone a preliminary change in Chyle. Lacteals. Saliva. Whether lacteals ab- sorb any thing but chyle.