THE URINARY TRACT. 747 



granular, the outermost portion, on the contrary, being homogeneous and 

 shining. I have repeatedly seen, in acute interstitial nephritis, even the looped 

 tubules, which in this situation were considerably in creased in bulk, provided 

 with a coarsely granular reticulum nay, even with an indistinct, rod-like 

 structure. All these features become still more prominent by staining the 

 specimens with the chloride of gold after they have been soaked and washed 

 for several days in distilled water. This reagent, in a half per cent, solution 

 brought in contact with the specimens for forty minutes, renders sections 

 from the normal kidney of a brown- violet hue, slightly increasing the distinct- 

 ness of the reticular structure of the epithelia. In the inflamed kidneys of 

 man, the epithelia of a great many of the ascending, irregular, and convo- 

 luted tubules, upon being stained with the chloride of gold, as above described, 

 became dark violet. With higher powers of the microscope we can ascertain 

 that it is the coarse reticulum, the bulky rods, and the homogeneous masses 

 sprung from coalescence, as it were, of the rods, which exhibit the deepest 

 gold stain. 



As it is the tubuli uriniferi which have the rod-like structure, which in 

 Heidenhain's experiments with indigo sulphate are the only ones which 

 are colored by it, so in the inflamed kidney it is only these tubules that 

 become colored by the gold. It seems reasonable to suppose, from the 

 effect of these reagents, that the epithelia with rods, perhaps by virtue of 

 their having more living matter and a more bulky reticulum, are of most 

 importance in secreting or forming the extractive matter of the urine. 



In the inflamed kidneys, in which the violet coloration was produced, no 

 doubt the reticulum of the epithelia, owing to the inflammatory process, was 

 considerably increased in bulk. The most marked violet stain was exhibited 

 by a number of the convoluted tubes and by irregular and ascending tubules. 

 We know that living matter is considerably increased in amount in the inflam- 

 matory process, and are justified, consequently, in maintaining that the 

 reticulum and the rod-like formations within the epithelium, being part of the 

 reticulum, are formations of living matter. (See Fig. 3'37.) 



As to the significance of the rods, it may be inferred that they are in close 

 relation with the process of secretion. Obviously, the stream of liquid run- 

 ning from the neighboring blood-vessels through the epithelia toward the 

 liquids contained in the caliber, and vice versa, will be facilitated by an elon- 

 gated arrangement of the reticulum i. e., the rods. In a state of compara- 

 tive rest the rods lie close to each other nay, are coalesced into homogeneous 

 masses. In this condition the cement-substance between the epithelia is best 

 marked. In full activity of the epithelium, on the contrary, the rods will be 

 very distinct, will stand farther apart, and the cement-substance between the 

 epithelia will, in consequence, become indistinct. 



The Endothclia of the Urinary Tubules. While investigating the peculiarities 

 in the structure of epithelia of tubuli uriniferi in their normal condition, I 

 often observed the presence of flat, spindle-shaped bodies between the basis 

 of the epithelia and the adjacent so-called structureless membrane of the 

 tubule. These spindle-shaped bodies doubtless correspond to those flat, 

 nucleated formations which cover the inner surface of the structureless layer 

 in nearly all epithelial i. e., glandular formations. By most observers 

 they are regarded as endothelia belonging to the connective tissue subjacent 

 to the epithelial layers. V. Czerny was the first one to bring them to view in 

 other tissues, which he did by staining the specimens with the nitrate of 



