162 THE URINARY ORGANS. 



into the gland it can normally be easily stripped off from the 

 surface. 



The connective tissue permeating the renal parenchyma 

 (the intertubular or interstitial tissue) is a delicate tissue, very 

 small in quantity, penetrating between and supporting the 

 uriniferous tubules and vascular channels ; it consists chiefly 

 of the basement-membranes on which the tubules rest. Some 

 connective tissue also accompanies the vessels entering at the 

 hilurn, and in and beneath the lining of the renal sinus are 

 considerable quantities of fibrous, areolar, and adipose tissue. 



The uriniferous tubules (Fig. 66) are the secreting or gland- 

 ular elements of the kidney. They consist of long tubes, 

 which (except the larger collecting- ducts) are single and un- 

 branched. They are lined with a single layer of epithelium- 

 cells resting on a basement-membrane, and in different parts 

 of their course exhibit different divisions varying in arrange- 

 ment, form, and structure. The parts into which the tubules 

 are divided are, in their order, as follows : Malpighian body ; 

 neck ; proximal or first convoluted tubule ; spiral tubule ; 

 the loop of Henle (consisting of a descending limb and ascend- 

 ing limb) ; irregular tubule ; distal or second convoluted 

 tubule ; curved or arched tubule ; straight collecting tubule, 

 and tube of Bellini. 



The Malpighian body is a hollow spherical structure or ex- 

 panded sac forming the beginning of each uriniferous tubule. 

 Its wall is formed by a membrane called the capsule of Bow- 

 man, and into its cavity, but covered by its epithelium, pro- 

 jects a tuft of capillary bloodvessels called the glomerulus. 



The capsule of Bowman consists of a single layer of squam- 

 ous epithelium resting on a basement-membrane. It forms a 

 hollow spherical sac, the cavity of which at one point opens 

 into the proximal convoluted tubule through a small neck. 

 The layer of squamous epithelium is invaginated into the 

 cavity so as to form a complete covering for the glomerulus 

 (Fig. 67). 



The glomerulus is a tuft of capillaries coiled into a spherical 

 mass nearly filling the interior of the Malpighian body. 



The capillaries arise from a single afferent vessel, and unite 

 to form a single slightly smaller efferent vessel; these two ves- 

 sels enter and leave the glomerulus together, forming a sort 



