240 ELEMENTS OF HISTOLOGY. [Chap. xxx. 



propria of the tubule between the lining epithelium; 

 and, in some cases, even a delicate nucleated membrane 

 can be seen lining the surface of the epithelium next 

 the lumen. In the frog, the epithelium lining, the 

 Malpighian corpuscles, and the exceedingly long neck 

 of the urinary tubule, are possessed of long filamentous 

 cilia, rapidly moving during life. In the neck of 

 some of the urinary tubules in mammals there is 

 also an indication of cilia to be noticed. 



Heidenhain has shown that indigo- sulphate of 

 sodium, injected into the circulating blood of the dog 

 and rabbit, is excreted through certain parts of the 

 urinary tubules only viz., those which are lined 

 with " fibrillated" epithelium. He maintains that 

 this excretion is effected through the cell sub- 

 stance ; but, in the case of carmine being used as 

 pigment, I have not found the excretion to take place 

 through the substance of the epithelial cells, but 

 through the homogeneous interstitial or cement sub- 

 stance between the epithelial cells. 



315. II. The blood-vessels (Fig. 136). 



The large branches of the renal artery and vein 

 are situated in the submucous tissue of the pelvis, 

 and they enter, or pass out respectively from, the part 

 of the parenchyma corresponding to the junction of 

 the cortex and boundary layer, where they follow a 

 more or less horizontal course, and give oft', or take up 

 respectively, smaller branches to or from the cortex 

 and medulla. 



(1) In the cortex the arterial trunks give off to 

 the cortex small branches, which singly enter the 

 labyrinth in a direction vertical to the surface of the 

 kidney. These are the interlobular arteries. Each of 

 these, on its way towards the external capsule of the 

 kidney, gives off, on all sides of its circumference, 

 shorter or longer lateral branches; these are the 

 afferent arterioles for the Malpighian corpuscles, each 



