i6 4 THE MICROSCOPE. 



tain diseases is such that in some of those of the kidney it is impos- 

 sible to make a positive diagnosis without its aid, and in all it will 

 diffuse some light on their nature by a careful examination of the 

 urine under a one-fourth inch objective. However, to obtain reliable 

 data in diagnosis, no hasty or occasional examination is of much 

 value, but only repeated, careful and continued observation will reveal 

 the disease and indicate its course. 



The general practitioner must have a definite knowledge of the 

 histological structure and of the pathology of the kidney, in order 

 that the instrument may be of any aid to his diagnosis. 



Physiology teaches that the function of the kidneys is to take 

 from the system nitrogen and water, and at the same time from the 

 blood many of its salts. Hence, the excretion is the most accurate 

 index of the condition of the organs. Here, then, we have ground 

 for the maxim, "Whenever in doubt of a positive diagnosis, examine 

 the urine carefully and thoroughly." Da Costa says: "But to glean 

 the full benefit from an analysis of the urine, we must be acquainted 

 with its complex composition, and be able to explore it qualitatively 

 and quantitatively, and be accustomed to examine its deposits with 

 the microscope." 



The normal salts of the urine, the urates, uric acid, the phos- 

 phates, creatine and creatinine, are all most readily distinguished by 

 the microscope, but the chlorides and sulphates are more easily 

 found by chemical tests. The significance of these normal salts, 

 when present in excess, cannot be spoken of in this paper. 



Of the abnormal substances found occasionally in the urine, we 

 find sugar, bile and leucine better detected by chemical means until 

 microscopy is more advanced; but these substances, when found, do 

 not indicate disease of the kidney, nor does tyrosine, which is readily 

 detected by its long, shining, crystal needles, under a moderately 

 high power. 



The oxalates are most readily detected with the microscope, 

 but their significance does not pertain to our topic, though their 

 presence denotes some nervous or gastric derangement. 



In considering blood as a foreign element found in the urine, a 

 careful study is necessary to localize the origin of the hemorrhage, 

 and this can only be accomplished with the microscope. When the 

 hemorrhage denotes a lesion of the kidney, the instrument shows 

 the renal epithelium, which is characterized by being globular, and 



