INTRINSIC ABSORPTION. 627 



these vessels after death. There are also muscular fibres in the inter- 

 alveolar septa of the lymphatic glands. Fifthly, the semilunar valves 

 found in pairs in the interior of the larger lacteals, both in the walls 

 of the intestine and in the mesentery, must determine the movement 

 of the contained chyle, always in the same direction, by whatever force 

 such movement may be induced. In this way, even the pressure of 

 the abdominal walls and viscera must assist the onward flow of the 

 chyle. Its direction necessarily coincides with that of the free margins 

 of the valves, viz., towards the thoracic duct, all retrogression of the 

 chyle in the direction of the intestine, being effectually prevented. 

 Lastly, the quick motion of the blood in the great veins at the root of 

 the neck, into which the thoracic duct opens, and the effects of inspi- 

 ration, are also causes of a certain vis a front e, or force from before, 

 which draws the lymph or chyle from that duct into the veins. The 

 descent of the diaphragm in inspiration, acts not only by removing 

 pressure from the great veins in the thorax, but also by increasing the 

 pressure on the abdominal lymphatics and the lower end of the thoracic 

 duct. 



The quantity of mixed lymph and chyle poured into the blood in 

 twenty-four hours, has been estimated, from experiments in animals, 

 to be, in an adult man, nearly 29 Ibs., of which the smaller proportion 

 is chyle, the rest being lymph. (Bidder and Schmidt.) It has been 

 ingeniously suggested by Vierordt, that, if the absorption of fat be 

 supposed to take place exclusively by the lacteals, and the composi- 

 tion of the chyle be assumed to be uniform, the -daily quantity of chyle 

 may be calculated from the daily quantity of fat taken in the food. 

 Thus, the quantity of fat consumed in the day being taken to be 

 3 oz., and the chyle, to contain 3 per cent, of fatty matters, the 

 quantity of this fluid formed daily would be about 100 oz., or 6J Ibs. 

 The chyle is a highly nutrient fluid. It adds not only fatty matter, 

 but, like the lymph, a certain amount of fibrin or fibrinogen, albumen, 

 extractives, and salts, and also a number of granules and proper cor- 

 puscles, to the blood. The gradual entrance of these into the blood, 

 is of some importance in the maintenance of the proper composition 

 of that fluid, and, accordingly, nutrient substances are absorbed rather 

 more slowly than those which are not nutrient. The more concen- 

 trated the products of digestion, however, the more rapid is their 

 absorption ; at least this is true of sugar and albuminose. (Becker, 

 Funke.) 



Intrinsic Absorption. 



The special process, by which the fluid or solid parts of the living 

 body, are interstitially removed, the so-called intrinsic absorption, is 

 usually described with the simpler phenomenon of general absorption. 

 But it is a different and more complex process, implying a previous 

 liquefaction, or fine disintegration, of the solid particles of the absorbed 

 tissues, before these can enter the lymphatics or bloodvessels concerned 

 in their removal. It is in part, therefore, a nutritive or denutritive 

 process. 



