124 STRUCTURE OF THE KIDNEY. 



pyramid of Malpighi, from its base to its papilla, was caused 

 by the union of many of the ducts together, into common tubes, 

 so as to constitute lesser s pyramids, called the pyramids of 

 Ferrein, (Pyramides Fcrreinei.) The ducts of each of these 

 pyramids, subsequently unite together, so that the conver- 

 gence is uniform down to the papilla, where for the whole of 

 the tubes of each conoidal body, there appears to be but from 

 twenty to thirty terminal orifices. In each conoidal body, the 

 pyramids of Ferrein, are said by that anatomist to be seven 

 hundred in number, which, as the number of cones in a kidney 

 are upon an average about fifteen, would make the whole 

 number ef pyramids in the kidney, ten thousand five hundred. 

 Again, each of the pyramids of Ferrein, is said at its base to 

 be composed of many hundred separate tubes, each of which 

 tubes, according to Eysenhardt, is composed of twenty smaller 

 ones : but the observations of this latter writer, even by the 

 German anatomists, are considered rather as a-n exaggeration. 

 The exact mode of origin of the tubuli uriniferi has been 

 long a question of doubt. According 10 Krause and Mullci 

 and most modern observers who have investigated this subject, 

 they originate as closed tubes, like the ducts of other glands. 

 Mr. Bowman as before noticed, considers the closed tubes to be 

 expanded into pouches at their ccecal ends for the purpose of 

 lodging the glomerules each pouch being pierced by two orifices, 

 for the accommodation of the entering artery and efferent vein. 

 These ducts, when examined with the microscope in the 

 cortical portion, appear two or three times less in diameter, 

 than the tubuli seminiferi, and therefore invisible to the naked 

 eye, though they are still much larger than the capillary 

 blood-vessels, which form in the cortical structure of the kid- 

 neys a very minute net-work. The ducts of the cortical 

 portion (ducti Ferreinei,) anastomose frequently with one 

 another ; they are flexuous and closely aggregated together, 

 which gives to the cortical matter the appearance of a solid mass. 

 From the minute currents of blood with which these vessels 

 supply the glomerules and the walls of the ducts, the secretion 

 of urine, takes place ; a part of the contents of the blood-ves- 

 sels permeating their walls, and undergoing in the transit proba- 



