ABSORPTION, STORAGE, AND ASSIMILATION 179 



connective tissue around the heart. The stored-up fat is 

 redissolved as needed, and enters the blood, where it again 

 becomes available to the active cells. 



3. The proteids form a part of all the tissues, and for 

 this reason are stored in larger quantities than any of the 

 other food substances. The large amount of proteid found 

 in the blood may also be looked upon as storage material. 

 The proteids in the various tissues are spoken of as tissue 

 proteids, and those in the blood as circulating proteids. 

 The proteids of the tissues serve the double purpose of 

 forming a working part of the cell protoplasm, and of sup- 

 plying reserve food material. That they are available for 

 supplying energy, and are properly regarded as storage 

 material, is shown by the rapid loss of proteid in starving 

 animals. When the proteids are eaten in excess of the 

 body's need for rebuilding the tissues, they are supposed 

 to be broken up in such a manner as to form glycogen and 

 fat, which may then be stored in ways already described. 



General Facts Relating to Storage. The form into which the food 

 is converted for storage in the body is that of solids the form that 

 takes up the least amount of space. These solids are of such a nature 

 that they can be changed back into their former condition and, by dis- 

 solving, reenter the blood. 



Only energy-yielding foods are stored. Water and salts, though they 

 may be absorbed in excess of the needs of the body, are not converted 

 into other substances and stored away. Oxygen, as already stated (page 

 1 08), is not stored. The interval of storage may be long or short, 

 depending upon the needs of the body. In the consumption of stored 

 material the glycogen is used first, then as a rule the fat, and last of 

 all the proteids. 



Storage in the Food Canal. Not until three or four 

 hours have elapsed are all the nutrients, eaten at a single 

 meal, digested and passed into the body proper. The un- 

 digested food is held in reserve, awaiting digestion, and 



