610 SPECIAL HISTOLOGY. 



also yielding up certain of its own constituents (water and salts), and 

 thus, at last, becomes true urine. 



As regards the chemical composition of the kidney, we know very 

 little. Frerichs (1. c. p. 42) found, in a healthy kidney, 16-30-18& solid 

 matter, 72-73-70 water. Of the former, the fat amounted to 0-63-0-lS, 

 although, according to Owen Rees, it may amount to 1-86 ; the greater 

 portion, however, is probably albumen, with regard to which, Ludwig 

 especially has shown, that it exists in large quantity in the kidney, a 

 fact that, from the micro-chemical characters of the epithelial cells of 

 the tubuli uriniferi, cannot be wondered at. 



In the higher animals, the secretion of the urine takes place without 

 any formation or dissolution of cells, and consequently the normal urine 

 just evacuated contains no morphological elements. It is only occa- 

 sionally that ejrithelial cells from the urinary passages, especially from 

 the bladder and urethra, occur in it ; but we almost always find mucus 

 from the same localities, forming clouds or a light sediment, occasionally 

 with mucous corpuscles; hnd lastly, spermatic filaments after emissions. 

 In inflammations, hemorrhages, exudations, fatty kidney, we find pus 

 corpuscles, oil drops, blood globules, blood, and fibrinous coagula, moulded 

 in the tubuli uriniferi, in the form of cylindrical casts, and epithelium 

 from the tubuli, isolated or in continuous strings or tubes. Sedimentary 

 deposits of the salts of the urine are readily formed as the products of 

 decomposition. All normal urine without sediment, at a mean tempera- 

 ture, undergoes an acid fermentation, under the influence of the mucus 

 contained in it; and whilst fermentation and filamentary/^?^' are de- 

 veloped, forms, from the decomposition of the urinary coloring matter, 

 lactic or acetic acid, in consequence of which uric acid is set free from 

 its compounds and deposited, in the form of rhombic or prismatic crys- 

 tals, colored yellow or reddish by the coloring matter of the urine. 

 Sooner or later the acid disappears, and from the decomposition of the 

 urea, perhaps also of the coloring matter, the urine becomes ammoniacal 

 and alkaline, with large colorless pyramidal prisms, or needles grouped 

 in a stellate fashion and soluble in acetic acid, of the triple phosphate of 

 magnesia and ammonia, which, intermixed with numerous infusoria 

 (vibriones and monades) form a superficial pellicle, and with granules of 

 urate of ammonia, and also, it may be, of carbonate of lime, a white 

 sediment. Under conditions not as yet known, and rarely, hexahedral 

 prisms of cystin appear in the urine ; more frequently, after the use of 

 drinks containing carbonic acid, and also in pregnant women, we find 

 the octohedrons of oxalate of lime insoluble in acetic acid. If the quan- 

 tity of uric acid be augmented, as after the inordinate use of nitrogenous 

 food with deficient exercise, in impaired digestion, fevers, &c. a more or 

 less abundant yellowish precipitate of urate of soda, in the form of 



