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196 ABSORPTION. 



the animal was immediately poisoned. The bloodvessels, therefore, are 

 not only capable of absorbing fluids from the intestine, but take them 

 up even more rapidly than the lacteals. 



The entrance of digested materials into the bloodvessels of the intes- 

 tine is readily demonstrated in a similar way. After the digestion of 

 food containing a mixture of albuminous and starchy ingredients, both 

 sugar and albuminose are to be met with in the blood of the mesenteric 

 and portal veins. Digested and emulsioned fatty matters may also be 

 distinctly followed, in their passage through the same channels, by the 

 turbid and chylous aspect which they communicate to the portal blood. 

 It is easy to see that the blood of the portal system, in the carnivorous 

 animals during digestion, contains fatty matter in a state of minute 

 subdivision, similar in appearance to that found in the chyle and in the 

 substance of the villi, often so abundant as to communicate a turbid 

 appearance to the serum after coagulation; and various observers 

 (Lehmann, Schultz, Simon), in examining the blood from different parts 

 of the body, have also found the blood of the portal system consider- 

 ably richer in fat than that of the arteries or of other veins, particularly 

 while intestinal digestion is going on with activity. 



Absorption by the Lacteals. The absorption of digested materials, 

 but more particularly of the fatty matters, is also accomplished by the 

 lymphatics or lacteals of the small intestine. These, however, do not 

 form a distinct class of vessels by themselves, but are simply a part of 

 the great system of lymphatic or absorbent vessels, which are to be 

 found everywhere in the integuments of the head, the parietes of the 

 trunk, the upper and lower extremities, and in the glandular and mus- 

 cular organs and mucous membranes throughout the body. Originat- 

 ing in the tissues of the above mentioned parts, they pass from the 

 periphery toward the centre, their branches converging and uniting with 

 each other like those of the veins, and passing, at various points in 

 their course, through certain glandular-looking bodies, known as the 

 lymphatic glands. 



The fluid generally contained in these vessels is called the " lymph." 

 It is a colorless or slightly yellowish transparent liquid, which is ab- 

 sorbed by the lymphatic vessels from the tissues in which they originate. 

 So far as regards its composition, it is known to contain, beside water 

 and saline matters, a small quantity of fibrine and albumen. Its ingre- 

 dients are evidently derived from, the metamorphosis of the tissues, and 

 are returned to the centre of the circulation to be eliminated by excretion, 

 or to undergo some new transforming process, the details of which are 

 not as yet fully understood. 



The lymphatic vessels of the intestine originate, as we have seen, in 

 the substance of the villi, where they commence by longitudinal spaces 

 lined with flattened epithelium cells, becoming provided, at a short dis- 

 tance from their origin, with thin, transparent, elastic coats, like those 

 of the capillary bloodvessels. After leaving the base of the villi they 

 become part of the lymphatic plexus, from which the main branches pass 



