1 68 SIXTEENTH LECTURE. 



I cannot presume that the highly complicated structure of 

 the mammalial and human kidney is hereby rendered appre- 

 ciable to every one ; let us, therefore, make a brief repeti- 

 tion. From the glomerulus (Fig. 154, g) and convoluted 

 cortical canals (/) the secretion reaches the descending (nar- 

 rower) side (<?), and from this into the ascending (d). From 

 the latter, the secretion passes through the intercalary piece 

 (c) into the efferent canal system (b and a). Our urine, there- 

 fore, passes through this long course. 



The frame-work substance consists, in the cortex, of a 

 scanty scaffolding of a connected, undeveloped connective 

 tissue. The latter is somewhat thicker in the medullary sub- 

 stance, especially below (Fig. 152, e). Cells are not wanting. 



We have the blood-vessels and lymphatics still remaining. 



The arrangement of the former vessels (Fig. 155) is the 

 most complicated, and, therefore, certain differences of opinion 

 still prevail in regard to it. 



In man the arterial and venous branches enter at the hilus 

 and pass into the interior, becoming more and more ramified. 

 After giving off branches to the capsule, the)' perforate the 

 latter external to the calyx of the kidney, an arterial branch 

 being accompanied, as a rule, by a venous branch. They 

 thus pass between the medullary pyramids to the bases of 

 the latter (a, h). They here assume an arched arrangement, 

 which is less complete in the arteries than in the veins. 



From the arteries now arise the coil-bearing branches (b), 

 which, keeping in the axis of the cortical pyramids, continue 

 as far as the surface, and give off laterally the vasa afferentia 

 of the glomeruli (c). In the lower animals, such as the frog 

 and the adder, the latter forms a single coil-shaped convolu- 

 tion. In man and the mammalia (Fig. 196), on the contrary, 

 we meet within the latter with the already mentioned (p. 98) 

 acute-angled divisions, which subsequently unite into the sin- 

 gle vas efferens. 



This (Fig. 153, d '; Fig. 155) is now resolved in a peculiar 

 manner into a capillary net-work (Key), forming at first an 

 elongated reticulum in the medullary rays (Fig. 153, e; Fig. 



