THE KIDNEYS. 



1879 



- 



Capsule 



Injected glomefulus, showing afferent and efferent vessels and 

 continuation into intertubular capillaries. X 250. 



Although as a matter of convenience the entire canal, from its commencement 

 in the Malpighian body to its termination on the papilla, has been described as the 

 uriniferous tubule, both geneti- 

 cally and functionally two dis- 

 tinct parts must be recognized. 

 These are the unbranched uri- 

 niferous tubule proper, which 

 includes all divisions from the 

 Malpighian body to the termi- 

 nation of the intermediate tu- 

 bule, and the duct-tube, which, 

 when traced from the papilla 

 towards the cortex, undergoes 

 repeated division until from a 

 single stem the number of con- 

 necting tubules is sufficient to 

 provide each uriniferous tubule 

 proper with its own excretory 

 canal. 



i. The Malpighian Body. This 

 structure, spherical in form and from 

 .01 2-. 020 mm. in diameter, consists 

 of two parts, the glomerulus and the 

 capsule. The former is an aggrega- 

 ion of tortuous capillary blood-ves- 

 sels into which break up the lateral 

 terminal twigs given off from the 



arteries as these pass between the cortical lobules towards the free surface of the kidney. The 

 lateral branches very short, often arched, and only .002-. 004 mm. in diameter spring at vary- 

 ing angles from all sides of the interlobular arteriole and enter the Malpighian body as the vas 

 afferens. On entering the glomerulus, the afferent vessel divides into from four to six twigs, 

 each of which breaks up into capillaries. These may anastomose and form a vascular complex 

 that may be filled from any branch ; not infrequently, however, such communication does not 



exist, each terminal twig 

 then giving rise to an iso- 

 lated capillary territory, 

 the entire glomerulus con- 

 sisting of vascular lobules, 

 each drained by its own 

 radicle. Sooner or later 

 all the channels of exit 

 unite to form the single vas 

 efferens, through which 

 the blood from the en- 

 tire glomerulus escapes. 

 The efferent vessel as it 

 emerges from the Mal- 

 pighian body is close to 

 the vas afferens, both usu- 

 ally lying on the side op- 

 posite to that occupied by 

 the neck of the capsule 

 from which the uriniferous 

 tubule is continued. In 

 consequence of the short 

 course and manner of ori- 

 gin of the twigs from the 

 interlobular arteries, the 



FIG. 1602. 



Capsule 



Neck 



Section of renal cortex, showing details of Malpighian hody ; glomerulus is 

 hich passes into obliquely cut neck. X 200. 



surrounded by capsule whi< 



glomeruli are disposed in 

 rows, somewhat like berries attached to a straight common stalk. 



The capsule of Bowman, the dilated beginning of the uriniferous tubule, almost com- 

 pletely invests the glomerulus with a double layer derived from the wall of the tubule, which 

 seemingly has suffered invagination by the vascular tuft. Such pushing in, however, is only 



