36 Feeds and Feeding. 



53. Absorption of proteins. — The amino acids and other products 

 of protein digestion are likewise absorbed from the small intestine 

 thru the villi. While still within the intestinal walls these rela- 

 tively simple products are joined together, thereby forming the 

 extremely complex molecules of the two proteins, serum albumin 

 and serum globulin. These newly formed proteins, which are the 

 common nitrogenous structural material of the body tissues, pass 

 on into the capillaries and enter the blood circulation along with 

 the glucoses. 



Mineral matter is taken up from the small intestines, and water 

 is absorbed all along the alimentary tract, from the stomach to the 

 large intestines. 



54. Distribution of absorbed nutrients. — We have seen that the 

 digested fats which are to nourish the body are poured into the 

 blood current by way of the lymphatics, while the glucoses, as such, 

 and the amino acids and other nitrogenous products of digestion, 

 changed to serum globulin and serum albumin, enter the blood di- 

 rectly thru the capillaries and veins. The veins from the small 

 intestine unite and become the portal vein, which passes the blood 

 thru the liver and on into the heart. The various nutrient mate- 

 rials, having been mingled with the blood, are carried thru the cir- 

 culation to the capillaries. 



These are so constructed that, when the blood finally reaches 

 them, the nutritive substances it carries pass thru their walls and 

 are mingled with lymph that bathes the myriad body cells. In this 

 manner all the nutrients, having been especially prepared and 

 transported, are available for the nourishment of every portion of 

 the body. Oxygen is taken into the blood thru the lungs, and 

 water and mineral matters are absorbed from the digestive tract. 

 All are carried by the arteries and pass thru the capillaries into 

 the lymph bathing the body cells. 



55. Use of the absorbed nutrients. — The absorbed nutrients, thus 

 transferred to all the tissues of the body, may be oxidized or 

 burned to warm the body, or to produce energy to carry on the 

 vital processes and to perform work, as shown in the following 

 chapters. In case more nutrients are supplied than are required 

 for these purposes, the excess may be transformed into body tissue 

 proper, as shown in Chapter V. The glucoses may be converted 

 into fats and stored as body fat, as may also the fats derived di- 

 rectly from the food fats. It is probable that the proteins of the 

 food, changed to serum globulin and serum albumin, may be broken 



