GLANDS. 107 



apices (papilla) converge towards the liilus, whilst 

 their bases are directed outwards, towards the surface 

 of the organ. The granular portion (cortical substance) 

 forms not only the peripheral substance or cortex of 

 the organ, surrounding the bases of the pyramids, 

 but it dips inwards between them, reaching nearly as 

 far as their summits. The free surfaces of the papillw 

 are pierced by numerous small orifices, rVth of a line 

 in diameter. Each of these orifices leads into a 

 straight canal, which, in its course, is constantly 

 dividing and subdividing, always into two branches, 

 and these are given off invariably at a very acute 

 angle. Having reached the base of the medullary 

 cone, all of these subdivisions of the primitive tube, 

 which thus far have pursued a perfectly straight 

 course, immediately become exceedingly tortuous, 

 and by their involutions and twistings, form the cor- 

 tical substance of the gland, each tubule terminating 

 at last by a bulbous extremity, which is in intimate 

 contact with a small tuft of blood-vessels called a 

 Malpighian body (PL XX. fig. I. 2, 3). 



It is noticeable that the line which limits the 

 base of each pyramid forms a series of indenta- 

 tions, and that the straight tubes* emerging from 

 the summit of the intervening projections, are sur- 

 rounded on all sides by tortuous tubules (fig. 



i.i). 



In accordance with this description it is obvious 

 that each primitive straight canal gives origin to a 

 fasciculus of tubes (pyramid of Ferrein, lobule of the 

 kidney) which pursue a straight course through the 

 substance of the medullary cones (tubes of Bellini), 



