EXAMINATION OF URINARY DEPOSITS. 173 



may be examined with the microscope, when the tufts will 

 probably be seen, colored pink by the admixture of purpu- 

 rine. If it be present only in small quantity, a few detached 

 needle-like or branched crystals may be seen. It is readily 

 soluble in alcohol and hot water, but not in cold water. 



Vesical Mucus and Epithelial Scales, which may be present, 

 are derived from the internal surface of the bladder and uri- 

 nary passages. The quantity is so small in healthy urine as to 

 be scarcely visible, until, after standing, it has subsided to the 

 bottom of the liquid in the form of a thin cloud. 



Extractive Matter, includes all the uncrystallizable organic 

 matter found in the residue of evaporated urine, which is 

 soluble in water or alcohol. When in excess, the urine ap- 

 pears more highly colored than usual, a large proportion of 

 what is termed extractive, consisting of coloring matter, as 

 purpurine, &c. 



Ammoniacal Salts appear to consist chiefly of the muriate 

 and the urate, the latter salt being the form in which the uric 

 acid present in the urine appears to be held in solution. 



The proportion of ammonia in healthy urine is quite small, 

 but in some diseases, especially in certain kinds of fever, it 

 increases considerably. 



Fixed Alkaline Salts may be obtained by incinerating the 

 evaporated residue of urine, when a white ash will be left, 

 consisting of a mixture of alkaline and earthy salts; the for- 

 mer may be separated from the latter by dissolving in water, 

 in which the earthy salts are insoluble. 



The alkaline salts, which in the healthy secretion usually 

 amount to thirteen or fourteen parts in one thousand, consist 

 of the sulphates of potash and soda, chloride of sodium, chlo- 

 ride of potassium, and phosphate of soda. The crystallized 

 residue, after slowly evaporating a few drops on a piece of glass, 

 usually has the appearance represented in Fig. 53. The cross- 



15* 



