272 ABSORPTION-LYMPH AND CHYLE. 



CHAPTER X. 



ABSORPTION LYMPH AND CHYLE. 



Absorption by blood-vessels Absorption by lacteal and lymphatic vessels Physiological anatomy of the 

 lacteal and lymphatic vessels Lymphatic glands Absorption by the lacteals Absorption by the 

 skin Absorption by the respiratory surface Absorption from closed cavities, reservoirs of glands, 

 etc. Absorption of fats and insoluble substances Variations and modifications of absorption- 

 Mechanism of the passage of liquids through membranes Lymph and chyle Properties and composi- 

 tion of lymph Origin and uses of the lymph Composition of the chyle Microscopical characters of 

 the chyle Movements of the lymph and chyle. 



DIGESTION has two great objects : one is to liquefy the different aliment- 

 ary substances; and the other, to b3gin the series of transformations by 

 which these are rendered capable of nourishing the organism. The matters 

 thus acted upon are taken into the blood as fast as the requisite changes in 

 their constitution are effected ; and once received into the circulation, they 

 become part of the nutritive fluid, supplying the loss which the constant 

 regeneration of the tissues from matters furnished by the blood necessarily 

 involves. The only constituents of food which possibly do not obey this 

 general law, as regards their absorption, are the fats. Although a small por- 

 tion of the fat taken as food may pass directly into the blood-vessels of the 

 intestinal canal, by far the greatest part finds its way into the circulation by 

 means of special absorbent vessels which empty into large veins. In what- 

 ever way fat enters the blood, it is not dissolved but is reduced to the condi- 

 tion of a fine emulsion. 



ABSORPTION BY BLOOD-VESSELS. 



That substances in solution can pass through the walls of the capillaries 

 and of the small veins, and that absorption actually takes place in great part 

 by blood-vessels, are facts which hardly demand discussion at the present 

 day. Soluble substances which have disappeared from the alimentary canal 

 have been repeatedly found in the blood coming from this part, even when 

 the lymphatics have been divided and communication existed only through 

 the blood-vessels ; and it has been shown that during absorption, the blood 

 of the portal vein is rich in albuminoids, sugar and other matters resulting 

 from digestion. 



In the mouth and oesophagus, the sojourn of alimentary matters is so 

 brief and the changes which they undergo are so slight, that no considerable 

 absorption can take place. It is evident, however, that the mucous mem- 

 brane of the mouth is capable of absorbing certain soluble matters, from the 

 effects which are constantly observed when the smoke or the juice of tobac- 

 co is retained in the mouth, even for a short time. In the stomach, how- 

 ever, absorption takes place with great activity. A large proportion of the 

 ingested liquids and of those constituents of food which are dissolved by the 

 gastric juice and converted into peptones is taken up directly by the blood- 

 vessels of the stomach. It may, indeed, be assumed, as a general law, that 

 alimentary matters are in great part absorbed as soon as their digestive 

 transformations in the alimentary canal have been completed. 



