482 PHYSIOLOGICAL CHEMISTRY 



Melanin. Melanin is an extremely rare constituent of urinary 

 sediments. Ordinarily in melanuria the melanin remains in solution; 

 if it separates it is generally held in suspension as fine amorphous 

 granules. 



(b) Organized Sediments 

 Epithelial cells. 

 Pus cells. 



Hyaline. 



Granular. 



Epithelial. 



Casts. 



Blood. 



Fatty. 

 Waxy. 

 .Pus. 



Cylindroids.' 



Erythrocytes. 



Spermatozoa. 



Urethral filaments. 



Tissue debris. 



Animal parasites. 



Micro-organisms. 



Fibrin. 



Foreign substances due to contamination. 



Epithelial Cells. The detection of a certain number of these cells 

 in urinary sediment is not, of itself, a pathological sign, since they 

 occur in normal urine. However, in certain pathological conditions 

 they are greatly increased in number, and since different areas of the 

 urinary tract are lined with different forms of epithelial cells, it becomes 

 necessary, when examining urinary sediments, to note not only the 

 relative number of such cells, but at the same time to carefully observe 

 the shape of the various individuals in order to determine, as far as 

 possible, from what portion of the tract they have been derived. Since 

 the different layers of the epithelial lining are composed of cells dif- 

 ferent in form from those of the associated layers, it is evident that a 

 careful microscopical examination of these cells may tell us the par- 

 ticular layer which is being desquamated. It is frequently a most diffi- 

 cult undertaking, however, to make a clear differentiation between the 

 various forms of epithelial cells present in the sediment. If skillfully 

 done, such a microscopical differentiation may prove to be of very 

 great diagnostic aid. 



The principal forms of epithelial cells met with in urinary sediments 

 are shown in Fig. 146, page 483. 



