110 SUMMARY OF ABSORPTION. 



into the intestine. The other is carried into the blood circulation. I be- 

 lieve that this separation is of a purely physical kind, and is accomplish- 

 ed by mere filtration, the elements of the bile all pre-existing in the blood. 

 However that may be, the separation in a chemical sense is very distinct, 

 for the nitrogenized ingredients are saved to the system, and earned into 

 the general circulation through the hepatic veins ; but the biliary mate- 

 Return of a Ild ^ Brought k ac k i nt tne intestine is a hydrocarbon tinctured 

 part to the with a little coloring matter, which, being on a rapid career of 

 retrograde metamorphosis, is prone to act as a ferment, and 

 therefore unfit to remain in the system ; accordingly, it is removed with 

 the excrement. The other portion, the hydrocarbon, which has been 

 brought into the intestine, is not yet done with ; advantageous use can 

 still be made of it. It can aid in the introduction of fats through the 

 villi into the lacteals, and, from its combustible nature, is of an equal value 

 to the system with the oils it thus helps to introduce. We may advan- 

 tageously trace the course which it follows, for in so doing we shall com- 

 plete our description of the function of absorption in its most general 

 sense. 



The fat matters which have been subdivided into portions of micro- 

 Manner of sc pi ca l minuteness, small globules, each of which is coated 

 action of over with a delicate film of albumen, and all brought therefore 

 *' into the state of an emulsion, can make their way by reason of 

 the peculiar properties of the investiture which thus covers them through 

 the pores of the villi into the lacteal. For my own part, I do not believe 

 that there is any passage through the epithelial cells, but that it is en- 

 tirely interstitial, and that it is not unlikely that the biliary constituent 

 aids in this progress. It signifies nothing that the spaces through which 

 the fat globules have to go are less than their own diameter ; they can 

 elongate into worm-like forms, just as, under the same circumstances, 

 blood-cells can do, and, the moment they reach the cavity of the lacteal, 

 reassume their sphericity by reason of their cohesion. The albumen 

 that now accompanies them in the liquid form, as the other chief ingre- 

 dient of the chyle, comes, for the most part, from the blood-vessels of 

 the villi. The chyle moves onward to the mesenteric glands, and makes 

 its passage through them either in naked tubes or through their pulpy 

 structure, is submitted to cell action and to arterial blood, undergoes the 

 morphological changes which have been described in the preceding chap- 

 ter, and, gaining the thoracic duct, is brought into the general circula- 

 tion. 



In the description here offered of the function of absorption, the agen- 

 cy of physical forces alone has been considered, and these I conceive to 

 be abundantly sufficient to enable us to account for all the phenomena. 



