146 EXCRETION. 



between the pyramids. The surface of the kidney is marked 

 by little polygonal divisions, giving it a tabulated appear- 

 ance. This, however, is simply due to the arrangement 

 of the superficial blood-vessels. The medullary substance 

 is arranged in the form of pyramids, sometimes called the 

 pyramids of Malpighi, from twelve to fifteen or eighteen in 

 number, their bases presenting toward the cortical substance, 

 and their apices being received into the calices at the pelvis. 

 Ferrein subdivided the pyramids of Malpighi into smaller 

 pyramids (the pyramids of Ferrein), each formed by about 

 one hundred tubes radiating from the openings at the sum- 

 mit of the pyramids toward their bases. 1 The tubes com- 

 posing these pyramids were supposed to pass into the corti- 

 cal substance, forming corresponding pyramids of convoluted 

 tubes, thus dividing this portion of the kidney into lobules, 

 more or less distinct. The medullary substance is firm, of a 

 darker red color than the cortical substance, and is marked 

 by tolerably distinct striae, which take a nearly straight 

 course from the bases to the apices of the pyramids. As 

 these striae indicate the direction of the little tubes that 

 constitute the greatest part of the medullary substance, this 

 is sometimes called the tubular portion of the kidney. 



There are few subjects connected with the physiological 

 anatomy of the organism that present greater interest than 

 the minute anatomy of the kidney ; and this is one of the 

 organs which has been most closely and persistently studied 

 by anatomists. Without referring in detail to the investi- 

 gations of Malpighi, 8 whose name is attached to the corpus- 

 cles of the cortical substance, Bellini, 3 who first studied the 

 straight tubes, Ferrein, 4 who described the tubes of the corti- 



1 FERREIN, Sur la structure des visceres nommes glanduleux, et particulierement 

 sur celle des reins et du foie. Memoires de I ] Academic Royale des Sciences, annee, 

 1749, Paris, 1753, p. 499, et seq. 



2 MALPIGHIUS, Opera Omnia, Lond., 1686, tomus secundus, DeRenibus. 



3 BELLINI, Exercitationcs Anatomicce dace de Structura et Usu Renum ut et de 

 Gustus Oryano, Lugd. Batav., 1711. 



4 Op. cit. 



