RENAL CALCULI 459 



The sulphate ion takes, therefore, two alkali ions at its excretion from the 

 body. The weaker an acid is, the smaller is its dissociation, the more hydro- 

 gen ions it can bind, and the more alkali it can take from the organism. 

 The excretion of hydrogen ions is necessary for the carnivora and omniv- 

 ora in order to maintain the neutral reaction, and this excretion is 

 effected above all by phosphoric acid. From the" disodium phosphate of 

 the blood is produced through the action of the kidney the monosodium- 

 phosphate of the urine, which dissociates in the urine and is the essential 

 cause of its acid reaction. 



The carbonic acid, when given up to the lung, fulfills the task of a 

 quantitative sparing of alkali to the organism. But into alkaline urine 

 varying quantities of H 2 CO 3 enter and fix alkalis. That is advan- 

 tageous for the herbivora since they consume in abundance the alkaline 

 salts of oxidizable acids, which constantly furnish the organism with 

 cations. But when a meat-eating animal produces an alkaline urine con- 

 tinuously without being furnished with sodium bicarbonate or alkalis of 

 organic acids, the entire organism must undergo a change leading first to 

 an alkali loss and second to a compulsion to remove by some other way the 

 hydrogen ions which it does not give off to the urine. 



Calcium Metabolism 



Calcium is brought to the organism in inorganic form in the food ; in 

 the milk in a complex protein phosphoric acid compound. The amount of 

 resorption is dependent on the reaction in the gastrointestinal canal since 

 in acids, calcium carbonate and phosphate are soluble. If the food is rich 

 in phosphates relatively less calcium is resorbed. Only a part of the re- 

 sorbed Ca appears in the urine. The amount of resorption is difficult to 

 determine because the intestine is also an important excretory path for 

 calcium. What portion of the fecal calcium has passed through the body 

 cannot be determined. That an alkaline reaction and a higher content of 

 soaps in the large intestine lead to an increased elimination of calcium 

 through the intestine has been shown especially by the podiatrists. 



The daily calcium need of the human adult is less than 1.29 gm. (-Ren- 

 wall (a) ). According to the investigations of Bertram, calcium equilibrium 

 can be maintained with less than 0.49 CaO gm. (= 0.2869 gm. Ca). Of 

 especial importance is the partition of excretion between kidney and in- 

 testine. According to Renwall 25.4 to 64.3 per cent of the total Ca goes 

 through the kidney in adults; 32 per cent in sucklings (Blauberg). The 

 cause of these great variations in the adult is still not clear ; probably the 

 kind and quantity of food have an influence. 



Healthy adults appear to possess a tendency to calcium equilibrium, 

 yet with a pure milk diet calcium retention takes place. The amount of 

 urine calcium is 0.33 gm. to 0.80 gm. CaO per day. 



