THE KIDNEYS. 



171 



a common cavity in the hilus, from which the ureter takes 

 origin. 



129. The straight tubes of which each pyramid is composed, 

 open by a group of orifices at the summit, and divide several 

 times as they pass backwards. They are the continuations 

 of the convoluted tubes which form the cortex. And if the 

 texture be carefully examined in the deep part of the cortex, 

 it will be seen, even with the naked eye, particularly in a 

 minutely injected kidney, that the striated appearance pro- 

 duced by the straight tubes of the pyramid is prolonged 

 outwards in a series of streaks, each of which is imbedded in 

 the granular-looking convoluted portions of the tubes. Such 

 a streak, with the convoluted tubes belonging to it, is distin- 

 guished as a pyramid of Ferrein. Thus, a group of tubules 

 forms a pyramid of Ferrein; a number of these have their 

 straight parts prolonged, and unite to form a simple kidney, 



Fig. 92. TEXTURE OF KIDNEY, semi- diagrammatic view. A, Tubules 

 and Malpighian corpuscles of two pyramids of Ferrein ; B, afferent 

 and efferent blood-vessels of Malpighian corpuscles, and capillary 

 networks. 



