108 GLANDS. 



and become tortuous in the cortical substance of the 

 organ (tubes of Ferrein). 



The straight tubes measure, on an average, rVth of a 

 line, their subdivisions, jVth of a line, the tortuous tu- 

 bules of the cortical substance aVth of a line, and their 

 bulbous extremities iVth of a line. A perfectly struc- 

 tureless basement membrane, scarcely Wo oth of a line 

 in thickness, forms the outer walls of these secreting 

 tubules, which is hardly distinguishable except when 

 denuded of its epithelium (PL XX. fig. II. 4). Its 

 internal epithelial lining, at least ten times the thick- 

 ness of the outer wall, is composed of a single layer 

 of many-sided cells, usually pale in their outlines, and 

 each containing a large and well-marked nucleus, 

 which is very clearly recognisable in the midst of its 

 transparent granular contents (fig. II. 5, 7). Fatty 

 degeneration of these epithelial cells is the principal 

 lesion of the urinary tubules in Bright's disease. 

 These two membranes, alone, constitute the walls of 

 the urinary tubules, as far as their bulbous or 

 expanded terminations, where another element makes 

 its appearance, which we shall proceed to examine. 

 Arteries. In the hilus of the kidney the renal artery divides 

 into about a dozen branches, which, arranging them- 

 selves between the medullary cones, penetrate the 

 cortical substance, and ultimately reach the surface of 

 the organ. In their course, which is almost recti- 

 linear, they give off a great many branches to the 

 lobes, as they traverse the spaces between them, and 

 some smaller arterioles, also, to the fibrous envelope 

 of the gland. The ultimate branches of the renal 

 artery, having gained the interior of the medullary 



