198 



ABSOKPTION. 



Fiff. 64. 



and may be followed thence through the thoracic duct, to the point 

 where it terminates in the left subclaviaii vein. 



It was owing to the opacity and visibility of the lacteals during diges- 

 tion that these vessels were discovered in 1622 by Asellius, who first 

 saw them on opening the abdomen of a dog, a few hours after the inges- 

 tion of food. The discovery of the general system of lymphatic vessels 



was made subsequently by Hud- 

 beck and Bartholin, in 1651 and 

 1653, and was consequent upon 

 the previous observations on 

 the lacteals of the abdomen. 



That the white color of the 

 chyle during digestion is really 

 due to the presence of fatty sub- 

 stances absorbed from the intes- 

 tine, is shown by the fact that 

 the intensity of this color is in 

 proportion to the quantity of 

 fat contained in the food. It 

 is generally less marked in her- 

 bivorous than in carnivorous 

 animals. According to the- ob- 

 servations of Tiedemann and 

 Gmelin, in a dog fed with fatty 

 matters the lacteals are abund- 

 antly filled with an opaque white 

 fluid, while in the same animal 

 fed with starchy matters alone, 

 the chyle is pale and but slightly 

 opaline ; and finally Bernard has 

 shown that if, in a dog after 

 several days fasting, a little 

 ether, containing fat in solution, 

 be injected into the stomach, 

 without the introduction of any 

 other food, at the end of a few 

 hours the lacteals are found 

 fully distended with milky chyle, 

 precisely similar in appearance 

 to that obtained during ordinary 

 digestion. 



Passage of Absorbed Materials into the Circulation. The products 

 of digestion, which are taken up by the bloodvessels and lymphatics of 

 the intestine, pass by two different routes into the general circulation. 

 The blood of the portal system, containing albuminose, sugar, and 

 molecular fat, is carried at once to the liver, where it traverses the 

 capillary vessels of this organ before reaching the vena cava and the 



LACTEALS AND LYMPHATICS, during 

 digestion. 



