398 



EXCRETION. 



Cortical Substance. In the cortical portion of the kidney, are found numerous tubes, 

 differing somewhat from the tubes of the pyramidal portion in their size and in the char- 

 acter of their epithelial lining, but presenting the most marked difference in their direc- 

 tion. These tubes are somewhat larger than the tubes of pyramidal substance and are very 

 much convoluted, interlacing with each other inextricably in every direction. Scattered 

 pretty uniformly throughout this portion of the kidney, are rounded or ovoid bodies, about 

 four times the diameter of the convoluted tubes, known as the Malpighian bodies. At 

 one time there was considerable difference of opinion with regard to the relation of 

 these bodies to the tubes ; but the researches of Bowman, Isaacs, and later anatomists, 



have established, without doubt, the fact that 

 they are simply flask-like, terminal dilatations 

 of the tubes themselves. 



As the result of recent researches, the cor- 

 tical portion of the kidney is now regarded as 

 presenting a delicate fibrous matrix, which 

 forms a sort of skeleton for the support of 

 the secreting portion with its blood-vessels. 

 The tubes of this portion are convoluted and 

 somewhat larger than the straight tubes, but 

 are continuous with them, terminating finally 

 in the Malpighian bodies. The researches of 

 late anatomists, however, particularly in Ger- 

 many, have shown that this simple view of 

 the course and termination of the tubes of the 

 cortical substance must be somewhat modified ; 

 although, as far as the anatomy of the organ 

 has any bearing upon our ideas concerning the 

 mechanism of the secretion of urine, the views 

 of physiologists need undergo no material 

 change. 



The tubes of the cortical substance present 

 considerable variations in size, and, instead of 

 a single system continuous with the straight 

 tubes and terminating in the Malpighian bod- 

 ies, we can distinguish three well-defined varie- 

 ties: 



1. The ordinary convoluted tubes, directly 

 connected with the Malpighian bodies. 2. 

 Small tubes, continuous with the convoluted 

 tubes, dipping down into the pyramids and 

 returning to the cortical portion in the form of 

 loops. 3. Large, communicating tubes, form- 

 ing a plexus connecting the different varieties 



FIG. n5.-Diagrammatic vieio of the Malpighian f tubeS with 6ach ther and fina11 ^ with thc 

 bodies and tubes of the kidney. (Sappey.) straight tubes of the pyramidal portion. 



11 \u 2 befo^!nUtnUt f h? e tube ; i, 3 i ' l\ t^^TS The relation of these tubes can be readily 

 E^^^V 5 ' 5 ' 5 ' $ 5 ' ' convofut ' ed ' tubes;' 6, understood by reference to Fig. 115. In trac- 



6, 66, 6, descending portions of the looped tubes . 



of Henle ; 7, 7, 7, 7, 7, ascending, larger portions of m g out the COUrse of the tubes, which recent 



tab^fd^ii^^wi^^BfflS'S'Sl observations have shown to be somewhat intri- 

 corticai and of the pyramidal substance. k cate, it will be found most convenient to com- 



mence with a description of the Malpighian 



bodies and to follow the course of the tubes from these bodies to their connections with 



the straight tubes of the pyramidal substance. 



