46 MICROSCOPICAL DIAGNOSIS. 



uroerythin. There are also various coloring agents introduced 

 from without with the drink, food, or medicine. Among these 

 are especially, santonin, rhubarb, and senna. 



The odor of urine is affected by various matters and it is 

 of no material value to the physician. 



Normal urine is either clear or only very slightly cloudy. 

 When it is turbid it is evidence that there is some abnormal 

 condition. It may be due to the presence of pifs, mucus, or 

 epithelium, or to the various sediments. 



Normal urine generally turns blue litmus red, that is, it 

 has an acid reaction. It may have an alkaline or neutral reac- 

 tion. If the urine has an alkaline reaction the red litmus 

 paper will become blue ; if the blue paper be allowed to dry 

 and in so doing turns red again, then the cause is due to 

 the presence of a volatile alkali ; or if a volatile alkali be pre- 

 sent then a glass rod moistened in hydrochloric acid and held 

 over the urine will cause a white cloud to arise. If the blue 

 color remains after drying then the cause lies in the presence 

 of a fixed alkali. If the alkaline reaction of the urine be 

 temporary, a few hours each day or for -a whole day now and 

 then, it does not bear with it any great value, and it must 

 be regarded rather as a physiological condition. If the urine 

 be permanently alkaline, however, much aid to a diagnosis can 

 be derived from the fact. Rademacher calls a condition where 

 the urine is constantly alkaline "an iron affection," that is, an 

 affection calling for tonic remedies. 



The specific gravity of the urine varies from 1005 to 

 1030. If it remains persistently below 1010 and at the same 

 time contains no sugar, the case is one of diabetes insipidus. 

 When the specific gravity is below 1015 it should be tested 

 especially for albumen ; but when it is 1030 and above, it 

 should be tested for an excess of urea and for sugar. 



If the urine be turbid and has a sediment after standing it 

 should be tested for albumen. About a drachm of the urine is 

 placed in a narrow test-tube and from ten to fifteen drops of 

 strong nitric acid added ; if albumen be present it will be pre- 

 cipitated. To a similar portion of the urine in a test-tube heat 

 is applied and the albumen, if present, is precipitated. The 

 urine should always have an acid reaction before applying the 



