84 THE KIDNEYS, BY C. LUDWIG. 



formed by the urinary tubes. Such stride emerging from the 

 medulla, and running to almost the extreme circumference of 

 the cortex, are termed medullary rays (processes of the pyra- 

 mids). The remaining portion of the cortex, excluding these, 



Fig. 138. Horizontal section of the kidney of a Dog, in which both 

 the urinary and blood vessels have been injected, p, Papillary re- 

 gion ; g, marginal region of the medulla ; r, cortex. The dark striae 

 of the medulla (h) represent fasciculi of urinary tubules, and they are 

 continued as medullary rays (m) in the cortex. The transparent in- 

 tervening portions of the medulla (6) correspond in position to the 

 fasciculi of bloodvessels of the intermediate layer. The transparent 

 portion of the cortex, beset with dots (glomeruli, c), indicates the 

 labyrinth. 



chiefly presents the tint of the injection thrown into the blood- 

 vessels ; and this part may be termed the renal labyrinth (or 

 cortex, in the more restricted sense of the word). 



The application of the microscope to the differently coloured 

 portions shows that each is composed of a great number of 

 canals, which are partly continuous with the bloodvessels, and 

 partly with the urinary passages. These two kinds of vessels 

 form by far the largest part of the substance of the kidney. 



