GLANDS. 109 



pyramids, shortly after their origin, pursue a course 

 parallel with the straight tubes of which they are 

 composed, and continue onward through the cortical 

 substance, towards the periphery of the gland. 

 Whilst in the pyramids there is nothing peculiar in 

 their distribution, but, as soon as they reach the cor- 

 tical substance, they begin to give off small branches, 

 at regular intervals (afferent vessels), in every direc- 

 tion, which penetrate the walls of the secreting tubuli, 

 and occupy the interior of their expanded extre- 

 mities (PL XX. fig. III. 1 ; fig. IV. 4, 5). Here, each 

 afferent vessel breaks up into a certain number of 

 branches, which, becoming exceedingly tortuous, inter- 

 twine with each other so as to form a little round 

 ball, or tuft, which is known as the Malpighian body 

 (glomerula of Malpighi, corpus MalpJiigianwii). bSS hian 



These little vascular balls completely fill the pouch- 

 like terminal expansions of the tubuli uriniferi, and it 

 can be recognised that their surfaces are entirely 

 covered by a layer of renal epithelium. We have 

 succeeded in demonstrating this relation between the 

 Malpighian tufts and the epithelium of the urinary 

 tubules on several occasions, in the kidneys of the 

 guinea-pig, and our researches into the structure of 

 the human kidney have led to the same result (PI. 

 XXVII. fig. IV. 5). 



A solitary vessel, of capillary size (the efferent Efferent vessel, 

 vessel), leaves the Malpighian tuft, traversing the 

 wall of its containing cavity, either alone, or in com- 

 pany with the efferent vessel, near which it is always 

 found; it immediately divides into a multitude of 

 ramifications, which anastomose with each other, and 



