xi FOODS IN THE TISSUES 143 



108. The Wastes. The oxidation of foods in the 

 cells gives rise to certain waste products that must be 

 removed. The albumins form ivater and carbon dioxid, 

 and ammonia compounds, as kreatin. From the sugars 

 and fats, carbon dioxid and water are the important 

 wastes. Salt and water leave the cells in the form in 

 which they reached them. 



These wastes are produced in the cell and then given 

 off to the lymph. What becomes of them ? Most of 

 the carbon dioxid enters the capillaries of the blood 

 and is carried back to the heart by means of the veins. 

 Then it goes to the lungs, where it is given off to the 

 air sacs and exhaled. The other wastes reach the blood 

 through the lymphatics. In the lymph spaces all over 

 the body there begin small lymphatic capillaries. Much 

 of the water, salts, kreatin, etc., enters the open mouths 

 of these tiny vessels and is drained away by them. 

 These wastes reach the blood through the great lymph 

 trunks that empty into the subclavian veins. Now the 

 wastes are in the blood. 



109. Changes in the Blood. Some of these products 

 may be of value to other cells and so are kept in the 

 blood. There are many organs of the body whose 

 chief business it is to change the blood as it circulates 

 through them. The liver is an organ of this kind. We 

 have learned some things about the liver in former 

 chapters. Besides doing the things mentioned before, 

 this large and important organ serves as a crematory for 

 certain waste products that come from the cells. Here 

 urea is manufactured from ammonia compounds. The 



