PHYSICAL PROPERTIES OF THE URINE. 675 



and the sum of the acid equivalents is greater than the sum of the basic 

 equivalents. This depends upon the fact that in the physiological 

 combustion of neutral substances (proteins and others) within the 

 organism, acids are produced, chiefly sulphuric acid, but also phosphoric 

 and organic acids, such as hippuric, uric, and oxalic acids, aromatic 

 oxyacids, oxyproteic acids and others. From this it follows that the 

 acid reaction is not due to one acid alone. The various acids take part 

 in the acid reaction in proportion to their dissociation, since, according 

 to the ion theory, the acid reaction of a mixture is dependent upon the 

 number of hydrogen ions present. Hence the theory that the acidity 

 is due entirely to dihydrogen phosphate is incorrect although this salt 

 takes such a great part in the acid reaction that its quantity is often 

 taken as a measure of the degree of acidity of the urine. 1 



The composition of the food is not the only influence which affects the degree 

 of acidity of human urine. For example, after taking food at the beginning of 

 digestion, when a larger amount of gastric juice containing hydrochloric acid 

 is secreted, the urine may be neutral or even alkaline. 2 As to the time of the 

 appearance of the maximum and minimum of acidity, the various investigators 

 do not agree, which may in part be explained by the varying individuality and 

 conditions of life of the persons investigated. It has not infrequently been 

 observed that perfectly healthy persons in the morning void a neutral or alkaline 

 urine which is cloudy from earthy phosphates. The effect of muscular activity 

 on the acidity of urine has not been positively determined. According to HOFF- 

 MANN, RINGSTEDT, ODDI, and TARULLI and VOZARIK muscular work raises the 

 degree of acidity, but ADUCCO 3 claims that it decreases it. Abundant perspira- 

 tion reduces the acidity (HOFFMANN). 



In man and especially in carnivora it seems that the degree of acidity 

 of the urine cannot be increased above a certain point, even though 

 mineral acids or organic acids which are burned up with difficulty are 

 ingested in large quantities. Under such conditions a different behavior 

 has been repeatedly observed between carnivora and herbivora. In the 

 first (and also in man) it has been found that the acids are in part neu- 

 tralized by the alkalies and alkaline earths of the body, but that the 

 excess of acid is combined with ammonia, split off from the proteins or 

 their cleavage products, and eliminated in the urine as ammonium salt. 

 In herbivora such a combination of the excess of acid with ammonia 



1 In regard to the acidity of the urine see the recent works of Ringer, Zeitschr. f . 

 physiol. Chem. 60; Henderson, Bioch. Zeitschr. 24, with Spiro, ibid., 15; De Jager, 

 Maly's Jahresb. 39 and Bioch. Zeitschr. 38; v. Skramlik, Zeitschr. f. physiol. Chem. 

 71; Klein and Moritz, Deutsch. Arch. f. klin. Med. 99; Quagliariello, Chem. Cen- 

 tralbl. 1912, 1, 506. 



2 Contradictory statements are found in Linossier, Maly's Jahresber., 27. 



3 Hoffmann, see Maly's Jahresber., 14; Ringstedt, ibid., 20; Oddi and Tarulli, 

 ibid., 24; Aducco, ibid., 17; Vozdrik, Pfliiger's Arch., 111. 



