746 



THE URINARY TRACT. 



power they are never so large as in the drawings, and seldom present the 

 straight, regular, and symmetrical appearance there represented. 



The pale, flat epithelia of the looped tubule proper do not, as a rule, exhibit 

 the rods. The columnar epithelia of the collecting tubules, on the contrary, 

 which are distinctly imbricated, especially in the kidney of the dog, exhibit 

 the rods more or less plainly. The columnar epithelium of the rabbit does, 

 however, show them. 



High powers (1000 to 1200) of the microscope corroborated the views 

 of Klein namely, that the rods are connected into a reticulum by means of 

 delicate filaments inosculating both with the wall of the nucleus around which 



the rods are located, and also with the 

 delicate reticulum in the inner portion of 

 the epithelia, next to the caliber, where 

 the rods are usually absent. It is striking 

 how the thickness of the rods differs in 

 the different epithelia of the same ani- 

 mal's kidney. Sometimes they are very 

 thin, beaded poles, with quite distinctly 

 marked interstices between them. In 

 this case the connecting filaments, run- 

 ning almost at right angles from rod to 

 rod, are easily discernible. At other 

 times the rods are rather bulky forma- 

 tions, having but extremely narrow in- 

 terstices between them. In this instance 

 the connecting filaments, as a matter of 

 course, are very short, and not easily 

 seen. In a third instance the outermost 

 portion of the epithelium is a compact 

 or homogeneous mass, in which no rods 

 can be observed at all. (See Fig. 336.) 



Another striking feature is the great 

 variety of appearances exhibited by the 

 cement -substance. Sometimes this is 

 plainly marked at regular intervals be- 

 tween the epithelia. Then the transverse 

 connecting filaments, the formerly so- 

 called thorns, are plainly visible. At 

 other times hardly any trace of cement- 

 substance is seen, but the reticular struct- 

 ure is present in a nearly uniform distribution throughout the epithelial 

 layer. Where the rods are slender, the nucleus, as a rule, is well defined ; 

 where, on the contrary, they are bulky, the nucleus is, on an average, not 

 very plainly marked. The sharpest definition of the nucleus is furnished by 

 the flat epithelia of the looped tubules in which the rods are absent. 



In inflamed kidneys of man I have repeatedly found the rods. Here the 

 rods of the epithelia throughout the tubules are clumsy and bulky, the whole 

 reticulum being enlarged, rendering the epithelium, with low powers of the 

 microscope, coarsely granular. In many instances the rods are not discernible, 

 as, in their place, a coarsely granular mass is present, pervading the whole 

 epithelial body ; or else the innermost portion of the epithelium looks coarsely 



FIG. 336. CONVOLUTED TUBULE 

 FROM THE KIDNEY OF A BAB- 

 BIT. LONGITUDINAL SECTION. 



N, nucleated columnar epithelium, 

 showing the rods ; E, endothelia ; I, in- 

 terstitial connective tissue, producing 

 the basement-layer. Magnified 1200 di- 

 ameters. 





