14 Influence of Inanition on Metabolism. 



experience in this laboratory. 30 In the later experiments, the determinations 

 of the carbon in the urine were made by the electrical method of Morse. 40 



The accuracy of these methods of analysis was frequently tested by burning 

 known substances, such as cane sugar or urea. 



Ether extract. The ether extract (crude fat) of food was made by the usual 

 method, by extracting 2 grams of the material (previously dried for the 

 determination of water) in a paper filter pocket and weighing the crude extract 

 thus removed. Feces receive special treatment in the analysis as discussed 

 beyond. 



Phosphorus and phosphoric acid. Total phosphorus in food, feces, and urine 

 was determined by fusion with sodium peroxide and subsequent conversion 

 to magnesium pyrophosphate. The modification suggested by Dubois, 41 which 

 includes the addition of a small amount of sodium carbonate to the fusion 

 mixture, was found to be very satisfactory. 



Phosphoric acid in urine was determined, as is usual, by titration with 

 uranium acetate, potassium ferrocyanide being used as an indicator. 



Sulphur and sulphuric acid. The sulphur was determined by fusion with 

 sodium peroxide and sodium carbonate in nickel capsules, precisely as in the 

 case of phosphorus. The sulphuric acid in the fused mass was precipitated as 

 a sulphate by barium chloride and water. The combined inorganic and ethereal 

 sulphates in the urine were determined according to the method of Folin, 43 

 which consists of heating urine with hydrochloric acid and potassium chlorate 

 and precipitating the sulphate as barium sulphate. An attempt was made to 

 obtain data regarding the neutral sulphur (S0 3 ) in urine by the difference 

 between the sum of the inorganic and ethereal sulphates (S0 3 ) and the total 

 sulphur (S0 3 ). The researches subsequently carried out by Folin 43 on the 

 difficulties of obtaining the precipitates of barium sulphate may tend to lessen 

 the value of the results obtained. 



Creatine and creatinine. The significance of the excretion of creatine and 

 creatinine, as pointed out by Folin, 44 led to the determination of these com- 

 pounds in the urine of the fasting subjects. The method of Folin for deter- 

 mining creatine and creatinine has been employed in this laboratory. This 

 depends upon the color reaction, noted by Jaffe, produced by the addition of a 

 solution of creatinine to an alkaline solution of picric acid. The depth of 

 color is compared with a half normal solution of potassium bichromate. From 

 the standard color of the normal solution the amounts of creatinine in unknown 

 solutions can readily be obtained. 



Chlorine was determined in urine by the Volhardt method. 



89 Benedict, Elementary organic analysis, Easton, Pennsylvania, 1900. 



"Amer. Chem. Jour. (1905), 33, p. 591. 



"Jour. Amer. Chem. Soc. (1905), 27, p. 729. 



u Amer. Jour. Physiol. (1905), 13, p. 52. 



"Jour. Biol. Chem. (1906), 1, p. 131. 



"Amer. Jour. Physiol. (1905), 13, p. 83. 



