408 



THE KIDNEYS. 



^'«- 2^1- According to the descrip- 



tion of Heidenhain, the 

 epithelium of these tubules 

 mainly consists of minute 

 thickly-set rod-shaped par- 

 ticles, which rest by one end 

 against the basement mem- 

 brane, whilst the other pro- 

 jects towards the centre of 

 the tube, surrounding the 

 nuclei, which are imbedded 

 in a certain amount of un- 

 altered protoplasm. He 

 states that it is the optical 

 sections of these " rods " 

 which produce the well- 

 known gi-anular appearance 

 of the epithelium of the 

 convoluted tubules. 



The descending limb of 

 the loop of Henle is very 

 small in diameter, but has a 

 distinct lumen, being lined 

 by flattened cells, each ^^-ith 

 an oval nucleus which pro- 

 duces a slight bulging into 

 the interior of the tube (fig. 

 2S9, c. a ; fig. 290, 1). The 

 ascending limb is much wider 

 than the descending, but its 

 lumen is comijaratively 

 small, for the epithelium 

 approaches more in charac- 

 ter to that of the convoluted 

 tubules having- a granular 

 appearance, and almost fill- 

 ing the tube (fig. 289. Z' ; fig. 

 290, 3). The bend of the 

 loop is formed sometimes 

 by the larger, sometimes by 

 the smaller kind of tubule, 

 Schweigger-Seidel. 



Imbedded among the 

 convoluted tubules in 

 irregular rows between 

 the pyramids of Ferrein 

 are the Malpighian cor- 

 puscles. These are small 

 rounded bodies about 

 y-jo th of an inch in dia- 



Fig. 291. DI.4.GRAM.1IATIC REPRESENTATION OF A PART OP THE STRAIGHT AND CONVO- 

 LUTED Uriniferous Tubes with the Glomeruli (from Frey, after a drawing by 

 MiiUer). 



0, 0, t-wo large straight tiibes in the medullary substance of the pjTamid ; c, con- 

 voluted tubes with several of their terminations in the Malpighian capsules as in d ; 

 a, three arteries passing up the pyi-amid and dividing into branches to the glomendi ; 

 the efferent vessels are also seen, and the network of capillaries between them and the 

 veins. The looped tubules of Henle are not represented. 



