THE KIDNEY. 



207 



peculiar, and was first correctly described by Heidenhain. 

 According to this writer, the greater part of the cell-protoplasm 

 assumes the form of small, cylindrical bodies, the so-called 

 rods of HeidenJiaiU) giving the epithelium a stri- 

 ated appearance (Fig. 93). 



To exhibit these appearances, the cortical sub- 

 stance of a dog's or rabbit's kidney should be 

 cut into small pieces and immersed for twenty- 

 four hours or more in a 5 per cent, solution of 

 the neutral chromate of ammonia. After this 

 time has elapsed, a small piece of the gland is to 

 be placed on a slide and a drop of glycerine 

 added ; the specimen may then be teased and ex- 

 amined. Portions of the convoluted tubules will 

 be found floating about in the glycerine, and 

 should be closely scrutinized. By this mode of 

 preparation, individual epithelioid corpuscles can- 

 not be recognized ; on the contrary, they seem 

 to merge with one another. The tubule may be 

 regarded as made up of rods transversely dis- 

 posed, with nuclei embedded in a pulpy mass 

 that appears to fill its lumen, the whole envel- 

 oped by the membrana propria. The rods sur- 

 round the nuclei, and are not all of the same length. They 

 appear to be hollow, as shown by their sometimes containing 

 fatty granules. Here and there in the specimen a separate 

 corpuscle will present itself to the eye; in 

 such instances the rods can readily be made 

 out (Fig. 94, A). In the kidney of the rat 

 these bodies may be isolated with little diffi- 

 culty (Fig. 94, B). At one end the rods rest 

 against the membrana propria, to which they 

 are attached by a colloid material ; their other 

 extremity is lost in the protoplasm of the cap- 

 sale, which latter lies internal to them and 

 appears to have the character of a pulpy mass 

 containing nuclei. In the dog, the nucleus of 

 each cell is about midway between the lumen 

 and the membrana propria. It is surrounded by rods (Fig. 

 94, A). In the rat this is not the case (Fig. 94, B). Assuming 

 that the rods begin at the membrana propria, they are directed 



%*?&.*" 



A- 



xlio B ' kidn ' y f rat * 



