ioo HUMAN PHYSIOLOGY CHAP. 



a small duct called a lacteal. The fats and oils pass 

 through the walls of the villi and get into these little 

 lacteals ; but they have not yet reached the blood. 

 The lacteals from several villi unite and form larger 

 tubes, known as lymphatic vessels, which finally empty 

 into a single trunk about the size of a goose quill, called 

 the thoracic duct. The fats together with a small amount 

 of the other foods are carried up through the thoracic duct 

 and emptied into the left subclavian vein at the base of 

 the neck. Here they mingle with the blood and are 

 washed along to the right side of the heart. 



A very important change occurs in the fats in absorp- 

 tion, and during their passage through the lymphatics. 

 There are little swellings, lyi)iph nodes or glands, on the 

 small lymphatic vessels, in which the fats are changed. 

 The butter, lard, suet, goose oil, etc., that we eat are 

 here changed to human fat. Every animal has a kind 

 of fat peculiar to itself. In the thoracic duct and in 

 the blood of man we find neither lard nor tallow ; they 

 have been changed to human fat during absorption. 



We have traced the fats and oils into the blood and to 

 the right side of the heart. Let us now see how the 

 other foods get from the digestive canal to the right side 

 of the heart. 



79. The Other Foods. Peptones, sugars, salt, and 

 water are the other foods that we left in the intestines. 

 These pass into the cells of the mucous membrane and 

 then directly into the blood capillaries. The capillaries of 

 the stomach and intestines unite to form many veins, all 

 of which empty into the portal vein. The portal vein is 



