3 8o 



PHYSIOLOGICAL CHEMISTRY 



this change within the organism and is voided in the decomposed state. 

 Ammoniacal fermentation is ordinarily due to cystitis or occurs as the 

 result of infection in the process of catheterization. A microscopical 

 examination of such urine (Fig. 119) shows the presence of ammonium 

 magnesium phosphate crystals, amorphous phosphates, and not infre- 

 quently ammonium urate. 



Ingestion of acid fruits (oranges, lemons, peaches, etc.) causes 

 the formation of alkaline urine. This is due to the fact that the ash of 

 such fruits is alkaline and when the fruits are combusted in the body 

 carbonates are formed. On the other hand, bread, cereals, meats, etc., 

 yield an acid ash and an acid urine. 



Occasionally a urine which possesses a normal acidity when voided, 

 upon standing instead of undergoing ammoniacal fermentation as above 

 described, will become more strongly acid in reaction. Such a phe- 

 nomenon is termed acid fermentation. Accompanying this increased 

 acidity there is ordinarily a deepening of the tint of the urinary color. 



FIG. 120. DEPOSIT IN ACID FERMENTATION. 

 a, Fungus; b, amorphous sodium urate; c, uric acid; d, calcium oxalate. 



Such urines may contain acid urates, uric acidjungi, and calcium oxalate 

 (Fig. 120, above). On standing for a sufficiently long time any urine 

 which exhibits acid fermentation will ultimately change in reaction, 

 due to the inception of alkaline fermentation, and will show the micro- 

 scopical deposits characteristic of such a urine. 



Specific Gravity. The specific gravity of the urine of normal indi- 

 viduals varies ordinarily between 1.015 an d 1.025. This value is sub- 

 ject to wide fluctuations under various conditions. For instance, 

 following copious water- or beer-drinking the specific gravity may fall 

 to 1.003 or lower, whereas in cases of excessive perspiration it may rise 

 as high as 1.040 or even higher. Where a very accurate determina- 

 tion of the specific gravity is desired, use is commonly made of the 

 pyknometer or of the Westphal hydrostatic balance. These instruments, 



