684 ABSORPTION. 



IV. INTERNAL ABSORPTION. 



On this point but few remarks will be necessary, after the exposition 

 of the different vascular actions concerned in absorption. The term 

 comprehends interstitial absorption, and the absorption of recrementitial 

 fluids. The first comprises the agency by which the different textures 

 of the body are decomposed and conveyed into the mass of blood. It 

 will be considered more at length under the head of NUTRITION; the 

 second, that of the various fluids effused into cavities; and the third, 

 that which is effected on the excretions in their reservoirs or excretory 

 ducts. All these must be accomplished by one of the two sets of vessels 

 previously described; lymphatics, or veins, or both. Now, we have 

 attempted to show, that an action of selection and elaboration is exerted 

 by lymphatics; whilst we have no evidence of such action in the case 

 of the veins. It would follow, then, that all the varieties of internal 

 absorption, in which the substance, when received into the vessel, pos- 

 sesses different characters from those it had when without, must be 

 executed by lymphatics; whilst those, in which no conversion occurs, 

 take place by the veins. In the constant absorption, and corresponding 

 deposition, incessantly going on in the body, the solid parts must be 

 reduced to their elements, and a new compound be formed; inasmuch 

 as we never find bone, muscle, cartilage, membrane, &c., existing in 

 these states in any of the absorbed fluids; and it is probable, therefore, 

 that, at the radicles of the lymphatic vessels, they are converted into 

 the same fluid the lymph in like manner as the heterogeneous sub- 

 stances in the intestinal canal afford to the lacteals the elements of a 

 fluid the character of which is always identical. On the other hand, 

 when the recrementitial fluid consists simply of the serum of the Blood, 

 more or less diluted, there can be no obstacle to the passage of its 

 aqueous portion immediately through the coats of the veins by imbi- 

 bition, whilst the more solid part is taken up by the lymphatic vessels. 

 In the case of excrementitious fluids, there is reason to believe, that 

 absorption simply removes some of their aqueous portions ; and this, it 

 is obvious, can be effected directly by the veins, through imbibition. 

 The facts, connected with the absorption of substances from the interior 

 of the intestine, have clearly shown, that the chyliferous vessels alone 

 absorb chyle, and that the drinks and adventitious substances pass into 

 the mesenteric veins. These apply, however, to external absorption 

 only; but similar experiments and arguments have been brought forward 

 by the supporters of the two opinions, in regard to substances placed 

 on the peritoneal surface of the intestine, and other parts of the body. 

 Whilst some affirm, that they have entered the lymphatics ; others have 

 only been able to discover them in the veins. Mr. Hunter, having in- 

 jected water coloured with indigo into the peritoneal cavity of animals, 

 saw the lymphatics, a short time afterwards, filled with a liquid of a 

 blue colour. In animals, that had died of pulmonary or abdominal 

 hemorrhage, Mascagni found the lymphatics of the lungs and peritoneum 

 filled with blood; and he asserts, that, having kept his feet for some 

 hours in water, swelling of the inguinal glands supervened, with trans- 

 udation of a fluid through the gland; coryza, &c. M. Desgenettes 



