290 PHYSIOLOGICAL CHEMISTRY. 



3. Sublimation. Place a little benzoic acid in a test-tube and 

 heat over a flame. Note the odor which is evolved and observe 

 that the acid sublimes in the form of needles. 



4. Dissolve a little sodium benzoate in water and add a solution 

 of neutral ferric chloride. Note the production of a brownish-yel- 

 low precipitate (salicylic acid gives a reddish-violet color under the 

 same conditions). Add ammonium hydroxide to some of the pre- 

 cipitate. It dissolves and ferric hydroxide is formed. Add a little 

 hydrochloric acid to another portion of the original precipitate and 

 stand the vessel away over night. What do you observe? 



NUCLEOPROTEIN. 



The nubecula of normal urine has been shown by one investigator, 

 to consist of a mucoid containing 12.7 per cent of nitrogen and 

 2.3 per cent of sulphur. This body evidently originates in the uri- 

 nary passages. It is probably slightly soluble in the urine. Some 

 investigators believe that the body forming the nubecula of normal 

 urine is nucleoprotein and not a mucin or mucoid as stated above. 

 A discussion of nucleoprotein and related bodies occurring in the 

 urine under pathological conditions will be found on page 320. 



NH-CO 



OXALURIC ACID, CO 



NH 2 COOH. 



Oxaluric acid is not a constant constituent of normal human 

 urine, and when found occurs only in traces as the ammonium 

 salt. Upon boiling oxaluric acid it splits into oxalic acid and urea. 



ENZYMES. 



Various types of enzymes produced within the organism are ex- 

 creted in both the feces and the urine. In this connection it is 

 interesting to note that pepsin, gastric rennin and an amylase have 

 been positively identified in the urine. The occurrence of trypsin 

 in the urine, at least under normal conditions, is questioned. 



VOLATILE FATTY ACIDS. 



Acetic, butyric and formic acids have been found under normal 

 conditions in the urine of man and of certain carnivora as well as 

 in the urine of herbivora. Normally they arise principally from 



