432 URINE. 



the stethoscope and the pleximeter, he will acquire but little infor- 

 mation from a chemical investigation of the urine, which con- 

 ducted on such principles will necessarily rank amongst the most 

 slovenly experiments. 



With respect to the purely diagnostic investigation of the 

 urine, it may be observed that the application of the microscope, 

 and some few chemical reagents will, in general, afford all the 

 necessary means for answering the questions commonly demanded 

 in chemical inquiry. If the urine be acid, the microscope may 

 reveal, as we have already seen, mucus or pus-corpuscles (in the 

 erroneously-termed chylous urine, such, for instance, as is almost 

 constantly found to accompany pyelitis), epithelium, spermatozoa, 

 casts from the tubes of Bellini, blood-corpuscles, &c., and in 

 addition to these urate of soda, oxalate of lime and cystine ; if the 

 urine be alkaline, a microscopical investigation will easily enable 

 us to ascertain that the fluid contains only phosphate of magnesia 

 -and ammonia, urate of ammonia, and other morphological elements. 



In order to distinguish urate of soda from uric acid in a sedi- 

 ment, by the aid of the microscope, the urine should not be 

 heated, for this would dissolve the urate of soda, as has been 

 mentioned in vol. i., p. 214. 



If an apprehension be entertained of mistaking the molecular 

 masses of urate of soda for other molecules under the microscope, 

 a few drops of hydrochloric acid should be added to the object, 

 when rhombic crystals of uric acid will be formed. (Acetic acid 

 often acts imperfectly or very slowly.) 



In order to avoid confounding certain crystalline forms of the 

 triple phosphate with oxalate of lime, a little acetic acid should be 

 added to the microscopical object, as directed in vol. i., p. 42. 



The hexagonal tablets of cystine may readily be, and probably 

 often are, confounded with the analogous forms of uric acid. They 

 may, however, easily be distinguished under the microscope, on 

 the addition of acids ; since the crystals of uric acid, which are 

 generally yellow in colour, are insoluble in them, whilst the crystals 

 of cystine (which are generally colourless) very rapidly dissolve in 

 them. We have already spoken in vol. i., p. 178 of the chemical 

 means of recognising cystine. 



Other substances, such as urea, hippuric acid, uric acid (when 

 it is not contained in the sediment), albumen, sugar, the biliary 

 acidsj and bile pigment, can only ba chemically recognised in the 

 urine by the methods which we have already considered in the 

 first volume. 



