ABSORPTION. 173 



The fatty substances taken up by the portal vein, like those ab- 

 sorbed by the lacteals, do not at once enter the general circulation, 

 but pass first through the capillary system of the liver. Thence 

 they are carried, with the blood of the hepatic vein, to the right 

 side of the heart, and subsequently through the capillary system of 

 the lungs. During this passage they become altered in character, 

 as above described, and lose for the most part the distinguishing 

 characteristics of oily matter, before they have passed beyond the 

 pulmonary circulation. 



But as digestion proceeds, an increasing quantity of fatty matter 

 finds its way, by these two passages, into the blood ; and a time at 

 last arrives when the whole of the fat so introduced is not destroyed 

 during its passage through the lungs. Its absorption taking place 

 at this time more rapidly than its decomposition, it begins to ap- 

 pear, -in moderate quantity, in the blood of the general circulation ; 

 and, lastly, when the intestinal absorption is at its point of greatest 

 activity, it is found in considerable abundance throughout the 

 entire vascular system. At this period, some hours after the inges- 

 tion of food rich in oleaginous matters, the blood of the general 

 circulation everywhere contains a superabundance of fat, derived 

 from the digestive process: If blood be then drawn from the veins 

 or arteries in any part of the body, it will present the peculiar 

 appearance known as that of " chylous" or " milky" blood. After 

 the separation of the clot, the serum presents a turbid appearance ; 

 and the fatty substances, which it contains, rise to the top after a 

 few hours, and cover its surface with a partially opaque and creamy- 

 looking pellicle. This appearance has been occasionally observed 

 in the human subject, particularly in bleeding for apoplectic attacks 

 occurring after a full meal, and has been mistaken, in some instances, 

 for a morbid phenomenon. It is, however, a perfectly natural one, 

 and depends simply on the rapid absorption, at certain periods of 

 digestion, of oleaginous substances from the intestine. It can be 

 produced at will, at any time, in the dog, by feeding him with fat 

 meat, and drawing blood, seven or eight hours afterward, from the 

 carotid artery or the jugular vein. 



This state of things continues for a varying length of time, ac- 

 cording to the amount of oleaginous matters contained in the food. 

 When digestion is terminated, and the fat ceases to be introduced 

 in unusual quantity into the circulation, its transformation and 

 decomposition continuing to take place in the blood, it disappears 

 gradually from the veins, arteries, and capillaries of the general 



