PRACTICAL EXERCISES 



531 



this method is sufficiently satisfactory, but it is not usually easy to get 

 freezing of the distilled water till the undercooling is considerable, and 

 it has been shown that this introduces some error. 



Suppose the freezing-point of the distilled water on the scale of the 

 thermometer was 5-245 and that of the urine 3-625, the value of A 

 for the urine is 1-620. Since for most purposes it is sufficient to fix 

 the second decimal point, much smaller and less expensive thermometers 

 than the ordinary Beckmann may be employed. 



In the same way the freezing-point of blood-serum (or blood), bile, 

 and other physiological liquids can be determined. 



Systematic Examination of Urine. In examining urine, it is con- 

 venient to adopt a regular plan, so as to avoid the risk of overlooking 

 anything of importance. The following simple scheme may serve as 

 an example; but no routine should be slavishly followed, the object 

 being to get at the important facts with the minimum of labour. More 

 extensive information must be sought in the treatises on examination 

 of the urine for clinical purposes. 



1. Anything peculiar in colour or smell ? If the colour suggests 



blood, examine with spectroscope, haemin test, guaiacum test (pp. 76, 



272) ; if it suggests bile, test for bile-pigments by Gmelin's test (p. 462), 



and for bile-salts by Pettenkofer's test (p. 462) and by Hay's test 



(pp. 462, 528). 



2. Reaction. 



3. Sediment or not ? Sediment may be procured by letting the 

 urine stand in a conical glass, or in a few minutes by the centrifuge. 

 .If the appearance of the sediment suggests anything more than a little 

 mucus, examine with the microscope. The sediment may contain 

 organized or unorganized deposits. 



Organized Sediments. (a) Red blood-corpuscles (considerably altered 

 if they have come from the upper part of the urinary tract). 



(6) Leucocytes. A few are present in health. A large number 

 indicates pus. When pus is present the sediment may be white to the 

 naked eye. 



(c) Epithelium from the bladder, ureters, pelvis of the kidney or the 

 renal tubules. A few squamous epithelial cells from the urethra are 

 always present in normal urine. 



(d) Tube casts. 



(e) Spermatozoa (occasional). 

 (/) Bacteria. 



(g) Parasites (rare). 



(h) Portions of tumours (rare). 



Unorganized Sediments. 



IN ACID URINE. 



Uric Acid. Crystals coloured 

 brownish - yellow with urinary 

 pigment. Various shapes, espe- 

 cially oval ' whetstones,' rhom- 

 bic tables, and elongated crystals, 

 often in bundles (Fig. 177). 



Urates. Usually amorphous, in 

 the form of fine granules, often 

 tinged with urinary pigment, 

 sometimes brick-red. Soluble on 

 heating. On addition of acids 

 (including acetic acid) they dis- 



IN ALKALINE URINE. 



Triple Phosphate. Clear, col- 

 ourless, coffin - lid or knife - rest 

 crystals. Also deposited in the 

 form of feathery stars (Fig. 179). 



Calcium Hydrogen Phosphate 

 (' stellar ' phosphate), CaHPO 4 . 

 Crystals often wedge-shaped and 

 arranged in rosettes. May also 

 occur in a dumb-bell form. (A 

 phosphate of calcium is also occa- 

 sionally seen in weakly acid urine.) 

 (Fig. 1 8 1, p. 479.) 



