THE URINARY ORGANS. 611 



isolated or aggregated granules, is formed as soon as the urine cools, 

 and becomes redissolved when it is again warmed. If, under these cir- 

 cumstances, the acid fermentation is set up, very considerable sediments 

 of colored crystals of uric acid (brickdust sediment) are often thrown 

 down. In injuries of the bladder, the urine frequently becomes alkales- 

 cent with great rapidity, when the above-mentioned crystals of triple 

 phosphate at once make their appearance ; they are also very frequent 

 in pregnancy ; and when assuming the pellicular form above described, 

 were at one time regarded as a peculiar substance (Kiesteine). 



The occurrence of albumen, fibrin, and fat, within the tubuli urini- 

 feri, is, in my opinion, easily explained, upon the supposition, that in 

 such cases the circulation is obstructed, and an increased secretion of 

 the elements of the blood takes place in the Malpighian bodies and 

 tubuli uriniferi, in consequence of which the epithelium of those parts 

 which, as is well known, is found in these cases in considerable quantity 

 in the urine, is washed away, whence, of course, any further hindrance 

 to the continued passage of the above substances is removed. A per- 

 meation of fibrin through the epithelium is also conceivable, just as 

 much, for instance, as upon the mucous membrane of the respiratory 

 organs, although I do not believe that an increased pressure of such a 

 kind as to induce a transudation of fibrin could fail to affect the deli- 

 cate epithelium. When the epithelium is once removed, it becomes an 

 important question whether it is quickly restored ; and it appears to 

 me, that the frequent occurrence of small quantities of albuminous 

 matter in the urine often depends simply upon local deficiencies of the 

 epithelium caused in one way or another. 



Investigation of the kidney. The tubuli uriniferi are readily isolated 

 when the tissue of the organ is teased out ; the epithelium, membrana 

 propria, and canal being distinctly recognizable if blood-serum, or a 

 solution of albumen be employed to moisten it. Together with entire 

 tubules, there will be found in every preparation numerous epithelial 

 cells, separate, or in groups, or even, as especially in the pyramids, in 

 the form of long continuous tubules. The latter often present a pecu- 

 liar aspect, for the most part collapsing, exhibiting somewhat flattened 

 cells, and resembling vessels. Equally frequent are longer or shorter 

 tubes of the membrana propria, which, when much plicated, cannot 

 always at once be recognized. In the examination of the pyramids, 

 the extremely numerous vessels must not be confounded with the 

 " ducts of Bellini," or the epithelial casts that have escaped from them. 

 The connection of the tubuli uriniferi with the Malpighian bodies is 

 easily discerned in the kidney of the Frog and of Fishes, upon careful 

 teasing out of the structure ; but in Mammalia, also, it will rarely be 



