THE URINE, 



793 



except when precipitated in very thin plates. It is often col- 

 lected in star-shaped groups of varying sizes, and produces the 

 so-called brick-dust sediment. In super-acid urine, which is 



FIG. 358. URIC ACID. 



U, common crystals ; U"i, crystals from over-acid urine ; C/2, clusters (gravel) of uric acid 

 from the pelvis of the kidney. Magnified 300 diameters. 



often combined with gouty and arthritic processes, or with the 



formation of uric acid concretions in the bladder, it appears in 



peculiar spear-, comb-, and brush-shapes. The 



concretions originating in the pelves of the kid- 



neys (so-called uric acid gravel) are comparatively 



large masses, composed of minute crystals of uric 



acid. (See Fig. 358.) 



(2) Oxalate of lime is frequently mixed with 

 uric acid, and, if present in small quantities, has 

 no pronounced significance. Oxalic acid, being 

 a product of uric acid, has a special affinity for 

 calcium, and appears in the sediment often very 

 late and only in the shape of oxalate of lime. In 

 derangements of digestion (dyspepsia) and dis- 

 turbances of the nervous system (" nervousness," 

 " neurasthenia," etc.) its amount is greatly aug- FlG 359. Ox- 

 mented. It appears in the form of quadrilateral 

 octahedrons, with the characteristic letter-envel- 

 ope-like line in front view, while in edge view 

 the octahedral form is most marked. The refract- 

 ing power of these crystals is very high, and they 

 are without color. Their size varies from the smallest dot-like 

 squares up to crystals of quite considerable size, which, however, 



ALATE OF LIME. 

 o, ordinary crys- 



ifled soo 



