44 



examined are in their proper relations. Half fill the vial or 

 test-tube with defibrinated blood. Nothing can be seen until 

 the blood is properly diluted. Continue diluting until two 

 bands of oxy-hemoglobin appear in the spectrum. Note 

 their position, and which one disappears first when the solu- 

 tion is diluted far enough. 



221. Add a drop or two of ammonium sulphide solution 

 to reduce the oxy-hemoglobin. Note the result. 



222. Pass some illuminating gas through some blood for a 

 considerable time. Examine with a spectroscope. Add a 

 drop or two of ammonium sulphide. Compare this with 221. 



XVII. 



EXAMINATION OF URINE 



223. Urine in man is a transparent, light straw or amber- 

 colored water3' excretion derived from the kidneys, contain- 

 ing nitrogenous matter, salts and gases. The most abun- 

 dant constituents are water, urea, and sodium chloride. It 

 has a peculiar odor, bitter .saltish taste, and acid reaction. 

 The normal quantity in an adult is about 1500 cc. (2}^ 

 pints), in twenty-four hours, although there may be consid- 

 erable variation, dependent upon the pulmonary and cutane- 

 ous excretions. 



The specific gravity of normal human urine ranges from 

 1015 to 1025, and is taken by means of the urinometer. 

 Care mu.st be taken that the instrument is perfectly dry ; the 

 urine must be clear and free from air bubbles on the surface ; 

 the urinometer must not touch the sides of the vessel. 

 Urine constantly below 1015 is of low specific gravity and if 

 constant may indicate diabetes insipidus or chronic Bright's 

 disea-se. If above 1025 it is of high specific gravity, and if 

 pale, diabetes mellitus or sugar in the urine may be sus- 

 pected. 



