URINE. 327 



Some investigators claim that it is impossible to differentiate 

 between bile acids and bile pigments by this test. 



CH 3 



ACETONE, C = 0. 



GEL 



It was formerly very generally believed that acetone appeared in 

 the urine under pathological conditions because of increased protein 

 decomposition. It is now generally thought that, in man, the out- 

 put of acetone arises principally from the breaking down of fatty 

 tissues or fatty foods within the organism. The quantity of acetone 

 eliminated has been shown to increase when the subject is fed an 

 abundance of fat-containing food as well as during fasting, where- 

 as a replacement of the fat with carbohydrates is followed by a 

 marked decrease in the acetone excretion. Conditions are different 

 with certain of the lower animals. With the dog, for instance, 

 the output of acetone is not diminished when the animal is fed 

 upon a carbohydrate diet, is decreased during fasting and increased 

 when the animal is fed upon a diet of meat. 



Acetone and the closely related bodies, /?-oxybutyric acid and dia- 

 cetic acid, are generally classified as the acetone bodies. They are 

 all associated with a deranged metabolic function and may appear 

 in the urine together or separately, depending upon the conditions. 

 Acetone and diacetic acid may occur alone in the urine but /?-oxy- 

 butyric acid is never found except in conjunction with one or the 

 other of these bodies. Acetone and diacetic acid arise chiefly from 

 the oxidation of /3-oxybutyric acid. The relation existing between 

 these three bodies is shown in the following reactions : 



(a) CH 3 -CH(OH)-CH 2 -COOH + = 



jS-oxybutyric acid. 



CH 3 CO-CH 2 -COOH + H 2 0. 



Diacetic acid. 



(I)) CH 3 CO-CH 2 -COOH= (CH 3 ) 2 CO + C0 2 . 



Diacetic acid. Acetone. 



Acetone, chemically considered, is a ketone, di-methyl ketone. 

 When pure it is a liquid which possesses a characteristic aromatic 

 fruit-like odor, boils at 56-57 C. and is miscible with water, alcohol 

 or ether in all proportions. Acetone is a physiological as well as 



