68 PHYSIOLOGY FOR NURSES 



Under the influence of lipase, fats are broken up into 

 glycerin and free fatty acid. Alkaline salts of sodium, 

 potassium, magnesium, and calcium are present in the 

 small intestine, and these bases unite with the fatty 

 acids to form soaps. The ordinary toilet soap is a 

 similar union of sodium with fatty acid. The soaps of 

 sodium and potassium, certainly, pass into the small 

 lymph channels of the intestinal villi, being reconverted, 

 in passing through the absorbing cells, back into neu- 

 tral fat; i.e., the union of glycerin and fatty acid. This 

 food fat passes on in the lymph channels until it finally 

 gains entrance to the veins by means of the thoracic 

 duct and the right lymphatic duct, and by this means 

 it is distributed to the various parts of the body. Fat, 

 like carbohydrate, is an important source of energy. In 

 the body, it is finally reduced to the same forms that 

 carbohydrate is, carbon dioxide and water, being ex- 

 creted by the lungs and kidneys. A considerable 

 amount of the fat, if fed in excess, may be deposited in 

 the tissues, to serve as a reserve for possible subsequent 

 need. The amount of fat that is used for constructive 

 purposes may be disregarded. 



Under certain circumstances, there may be a disturb- 

 ance in the process of changing the fats to carbon diox- 

 ide and water. Inj such cases, incompletely oxidized 

 substances accumulate in the blood ; the so-called ' ' ace- 

 tone bodies," acetone, diacetic, and /^-oxybutric acid. 

 This condition is known as "acidosis," and may arise in 

 the course of diabetes mellitus or even in simple starva- 

 tion. The sodium carbonate of the blood plays an im- 

 portant part in carrying carbon dioxide from the tissues 

 to be excreted by the lungs, but these acetone bodies 

 require a considerable amount of alkali to neutralize 

 them, so that the normal sodium carbonate content of 



