CHAP. XXXIV.] STRAIGHT PORTION OF THE TUBES. 



491 



Fig. 235. 



pyramid, the large tubes near the apex may be said to divide 



dichotomously, so that the number of the individual tubes, which 



would be seen in a transverse 



section, increases as we proceed 



from the apices of the pyramids 



towards their bases, while their 



diameter gradually diminishes. 



In the latter situation there may 



be many thousand tubes, while 



the number of openings upon 



the extremity of the mamilla 



are comparatively very few in 



number. The tubes at their 



orifices vary in diameter, from 



fVio 1 */ fVio 1 r\f on in oli " Scction of Ingest tubes, b. Section of smaller 

 kllc IToO Ly iilc ~2QQ Ul dll IIICII, tubes, at a point previous to their opening into a larger 



while towards the base of the SS^SS^ttafBT" 



pyramid they do not exceed jLnify bSeSTtX! tSbefin 



^ of an inch. The aggregate matrix ' d ' Magnifled about 12 diameters ' 



capacity of the tubes at the base of a cone is enormously greater 



than that of the much smaller number of somewhat larger tubes 



at their orifices. 



The epithelium in this situation differs in character from that 

 in the convoluted portion of the 

 tubes ; the cells are smaller, more 

 transparent, and approach more 

 nearly to the scaly or tesselated 

 variety. They seem rather to 

 serve as a protective layer than 

 to share in the secreting func- 

 tion. The cells here are usually 

 very thin, approaching to squa- 

 mous epithelium in character; 

 and although the total diameter 

 of the tube is less than that 



Of the Convoluted portion, the Malpighian tuft from the horse. Theinjeclion 

 rliflTYipfpr nf flip ppntral pnnal i<4 has P ene *ted only to the capillaries. . 'I he 



diameter 01 trie central canal is artery 0>/ _ One of its tei . mmttl twigs (or the 



o-rpiifpr afferent vessel), d. The dilatation and mode of 



^JCcttci. breaking up of the terminal twig after entering 



T7"/?cp7? nf tli? Kidnon TllP the capsule. The division of the tuft into lobes, 



Vessels OJ me J^ianey. J.UC ^ ^ is well seen i, {. intervals between the 



renal arteries divide into four or lobes - Magnified about so diameters. 

 five branches, which enter the kidney at the hilum between the 

 vein and the ureter. These vessels are surrounded with a quantity 

 of fat. They pass between the papillse to the bases of the cones, 



K K 2 



Fig. 236. 



