DISEASES OF THE URINARY APPARATUS. 505 



vaginal walls. For this purpose a speculum ad hoc can advantageously 

 be used. It is clear that if it is thought desirable to examine the 

 bladder through the rectum, which is not absolutely impossible, the 

 vagina w411 be interposed between the arm and the urinary organs, and 

 the sensations experienced will, therefore, be much less clearly defined 

 (Fig. 226). 



In passing a catheter for the purpose of emptying the bladder the 

 end of the sound should be introduced under the valve of the meatus. 

 By slightly lowering the back end of the sound, the front end is lifted 

 above the cul-de-sac, and the operator at the same time pushes gently 

 forwards. It is then only necessary to lift the hand, and the sound 

 passes readily into the urethra and the bladder. 



Examination of the urine and even chemical analysis are of great 

 importance in diagnosing diseases of the urinary tract. 



From the clinical point of view very complete analyses are not neces- 

 sary, but the tests for albumen, sugar, bile pigments and indican are 

 absolutely indispensable; and the same is true of microscopic exami- 

 nation for ascertaining the presence or absence of epithelial cylinders, 

 blood corpuscles, pus corpuscles, etc. It is important also to note the 

 colour and odour and the quantity passed. 



These examinations are by no means difficult. Albumen is detected 

 by adding a few drops of acetic acid to the urine, and heating, or by 

 adding nitric acid and Esbach's liquid. Esbach's albumenimeter is suf- 

 ficiently exact to discover the approximate amount of albumen present. 

 Sugar is detected by the use of Fehling's solution, bile pigments by 

 nitric acid, and indican by adding a few drops of 10 per cent, chloride of 

 calcium solution and hydrochloric acid. Should indican be present a 

 more or less deeply tinted indigo blue circle appears, resulting from its 

 oxidation. 



Hippuric acid is precipitated by pure hydrochloric acid. 



