THE URINE. 219 



The best test of the existence of the blood in the urine is 

 the detection of the blood corpuscles by the microscope; 

 blood, however, may exist in the urine, and yet no cor- 

 puscles be detected, these having been dissolved by the acids 

 of the urine. Failing, however, to detect the blood discs, 

 if blood really be present, then the albumen, fibrin, and 

 hematin will still remain, and may be distinguished by suit- 

 able reagents. 



From the colour of urine no conclusion can be formed as 

 to the existence of blood in it, as urine of a deep blood colour 

 is sometimes met with, which on examination is found not to 

 contain any trace of blood. 



Pus in the Urine. 



It bas already been stated in these pages that no absolute 

 distinction exists between mucus and pus ; and, therefore, it 

 follows that it is in most cases impossible to determine, with 

 any degree of certainty, whether pus exists in the urine or 

 not. 



If, however, the sediment rendered with the urine want 

 the tenacity of vesical mucus, and contain the granular cor- 

 puscles common to mucus and pus, there is reason to suspect 

 that the fluid in question is really purulent. 



The diagnosis will however be greatly assisted by refer- 

 ence to the history and symptoms of the case ; thus if there 

 be rigors and hectic fever, the probability of the existence of 

 pus will be much strengthened. 



There is one circumstance which requires to be mentioned, 

 and which greatly increases the difficulty of discrimination 

 between mucus and pus. In some cases of purulent urinary 

 deposits the urine is alkaline ; now the effect of the action of 

 alkalies on pus is to convert it into a transparent and tena- 

 cious substance in every respect resembling mucus, and 

 which therefore cannot be distinguished from it. 



There are but few details interesting to the microscopist 

 connected with the Gastric, the Pancreatic and the Lacrymal 



