40i 



THE KIDNEYS. 



Fisr. 286. 



The external or cortical substance (a) is situated immediately within 

 the fibrous capsule, and forms the superficial part of the organ throu<?h- 



out its whole extent to the depth of 

 about two-iin^s, and moreover sends \^ ^(v^w. 

 prolongations inwards (5/7j/«/rt re;z?w/, ^ 

 or columnce Bertini) between the py- 

 ramids as far as the sinus and bases 

 of the papillfe. It is of a nearly uni- 

 form light crimson brown appearance, 

 and is soft and easily lacerated in di- 

 rections vertical to the surface. The 

 medullary portion of the kidney is 

 more dense than the cortical, and is 

 distinctly striated, owing to its con- 

 sisting of small diverging uriniferous 

 tubes, and to its blood-vessels being 

 arranged in a similar manner. There 

 are generally more than twelve p3'- 

 ramids, but their number is incon- 

 stant, varying from eight to eighteen. 

 Towards the papilla3 the pyramids 

 are of a lighter colour than the cor- 

 tical substance, but at their base 

 they are usually purplish and darker. 

 Excretory Apparatus. — On 

 squeezing a fresh kidney which has 

 been split open, a little urine will be 

 seen to drain from the papillge by 

 fine orifices on their surface. The 

 secretion is carried away and con- 

 veyed into the bladder by the ureter. 

 This long tube on being traced up 

 to the kidney is seen to be somewhat 

 enlarged, and then to expand, as it 

 enters the fissure, into a large funnel- 

 shaped dilatation named the 2)eh'is. 

 This, within the sinus, divides usually into three, but sometimes only 

 two primary tubular divisions, and these at length end in a larger 

 number of short, truncated but comparatively wide branches named 

 calices or infancVibula, which receive the papillae into their wide mouths 

 and are attached around the bases of those prominences, from which, 

 of course, they catch the issuing urine. 



A single calix often surrounds two, sometimes even three papillge, 

 which are in that case united together ; hence, the calices are in general 

 not so numerous as the papillae. The spaces between the calices are 

 occupied by a considerable amount of fat, imbedded in which are seen 

 the main branches of the renal vessels. 



Like the rest of the ureter, the pelvis and greater part of the calices 

 consist of three coats, viz., a strong external fibro-areolar and elastic 

 tunic, which becomes continuous around the bases of the papilljfi with 

 that part of the proper coat of the kidney which is continued into the 

 sinus ; secondly, a thin internal mucous coat, which, or at least its 

 epithelium, is reflected over the summit of each papilla ; and thirdly^ 



Fig. 286. — Plan of a Longitcdinal 

 Skction theough the Pelvis and 

 Substance of the Right Kidney. 

 One-half the natural size. 



a, tlie cortical substance ; 5, 5, broad 

 part of two of the pyi-amids of Mal- 

 pigbi ; c, c, the divisions of the peh-is 

 named calices, or infundibiila, laid open ; 

 c', one of these unopened ; cl, d, summit 

 of the pyramids or papillte projecting 

 into calices ; e, e, section of the narrow 

 part of two pyramids near the calices ; 

 p, pelvis or enlarged portion of the ureter 

 within the kidney ; u, the ureter ; s, 

 the sinus ; h, the hilus. 



