544 



THE TISSUES. 



The 



Fig. 375. 



n/t 



tubuli uriniferi are everywhere composed of a simple co- 



noidal epithelium resting upon 

 a strong basement-membrane, 

 5 (riiny to Tg^w of an inch thick, 

 external to which is no distinct 

 corium but merely the stroma, 

 consisting of a firm transparent 

 substance containing small gra- 

 nular cells (Todd and Bowman) ; 

 which, everywhere in the lobule, 

 connects its various structural 

 elements together. (Fig. 376.) 

 Being at the commencement in 

 the papillae ^ to T ^ of an inch 

 in diameter, their branches are 

 soon but T2 Vu- to gJ 8 of an inch; 

 but in the pyramids of Ferrein 

 they again expand to ^ to ^ 

 and in the cortical substance to 

 sl-g of an inch or less; though 

 again somewhat constricted just 

 before they end in the dilatation 

 receiving the Malpighian bodies, 

 3&TF to T2 Vtf of an inch wide. 

 The nucleated epithelial cells are 

 also larger in the tubuli contorti 

 (TIO o to ToVu of an inch wide, 

 an d soW to ^Vcr of an inch 

 thick); while in the straight 

 portion of the tubules they are 

 only one-half as wide, and 30*00 



Vertical section through a portion of a pyramid and the cortical substance belonging to it, of an 

 injected rabbit's kidney. The figure is half diagrammatic. The vessels are represented on the left 

 side, and on the right the course of the tubuli uriniferi. a. Arterise interlobulares with the Mal- 

 pighian bodies (6), and their vasa afferentia. c. Vasa efferentia. d. Cortical capillaries, e. Vasa 

 efferentia of the outermost bodies, proceeding to the superficial capillaries. /. Vasa efferentia of the 

 innermost tufts continuous with the arteriolse rectse (g, g, g). h. Capillaries of the pyramids which 

 are formed out of the latter, i. A venula recta, commencing at the papilla, k. Commencement of a 

 straight canal at the papilla. 1. Divisions of the same. ra. Convoluted tubes in the cortex, their 

 whole course not shown, n. The same at the surface of the gland, o. Their continuation in the 

 straight tubules of the cortex, p. Their connection with the Malpighian capsules. Magnified 30 

 diameters. (KSUUcer.) 



