238 



REN. 



monly named the tubes of Bellini, that anato- 

 mist having been the first to show their true 

 tubular character ; they are united by a firm 

 network of fibrous tissue in the substance of 

 which there are some large veins, which take, 

 for the most part, a straight course between 

 the tubes. No Malpighian bodies exist in the 

 medullary cones. 



The capsule of the kidney is a firm, white, 

 fibrous membrane adherent by its external sur- 

 face to the adipose tissue in which the kidney is 

 imbedded, and connected by its internal face 

 to the entire surface of the kidney. It sends 

 numerous fibrous processes into the cortical 

 substance, and small vessels pass from the sub- 

 stance of the kidney into the fibrous capsule. 

 These connecting bands between the kidney 

 and its capsule are easily torn when the cap- 

 sule is stripped from the surface of the kidney. 

 At the hilum of the kidney the capsule be- 

 comes continuous below with the ureter and 

 above with the fibrous layer of the pelvis ; at 

 the same point the blood-vessels receive an 

 investment from this fibrous membrane, which 

 is continued upwards with them until they 

 finally break up into minute branches about 

 the bases of the pyramids. 



Calyces, Infundibula, and Pelvis. The caly- 

 ces are membranous or fibre-mucous cylinders 

 which receive in their upper extremities the 

 apices of the mamillary processes. Where 

 the membrane is reflected over the apices of 

 the cones, it is perforated by numerous orifices 

 of the tubes of Bellini, from which a liquid 

 may be seen to escape when pressure is 

 applied to the cones. The calyces are less 

 numerous than the mamillary processes, two 

 or three mamillary processes being occa- 

 sionally received into one calyx. The caly- 

 ces unite into three small tubes, one cor- 

 responding with each extremity and one with 

 the central portion of the kidney ; these have 

 somewhat of a funnel shape, and are called 

 infundibula. The infundibula soon unite to 

 form the pelvis of the kidney, which is a mem- 

 branous reservoir of a flattened oval figure, 

 terminating below in the ureter. The pelvisand 

 infundibula are usually surrounded by loose 

 reticular and adipose tissue. The blood-ves- 

 sels of the kidney are placed in front of these 

 parts. The fibrous and mucous coats of the 

 ureter are continuous with those of the pelvis, 

 infundibula, and calyces. 



Before passing on to the description of 

 the minute structure of the kidney, it is de- 

 sirable to examine the position of the blood- 

 vessels about the medullary cones, so far as 

 this can be ascertained by the unaided eye. 



The renal artery, as it enters the hilum of 

 the kidney, breaks up into four or five branches, 

 and these again subdivide, a few of the 

 branches passing behind the pelvis, while the 

 greater number remain in front ; they pass up- 

 wards between the calyces enclosed in folds 

 of the fibrous membrane, and so they come 

 in contact with the sides of the medullary 

 cones. Each cone appears to be supplied 

 by two arterial branches, which, passing up 

 one on each side, form an anastomosing arch 



over the base of the cone (fig. 146). From 

 this arterial arch branches proceed in all di- 



Fig. 146. 



Section of the kidney, showing the position of the 

 arterial and venous branches by the sides of the 

 medullary cones, a, a, a, a, arteries ; b, b, b, veins. 



rections, the greater number passing into the 

 cortical substance. The venous branches in 

 this situation likewise form arches over the 

 medullary cones, and have the same general 

 arrangement as the arteries ; they unite into 

 four or five trunks which are placed in front 

 of the pelvis. There is no anastomosis be- 

 tween the arteries of neighbouring cones ; 

 each medullary cone, with its investing cortical 

 substance, corresponds with one of the sepa- 

 rate lobules of the embryo kidney; and al- 

 though in the fully developed human kidney, 

 scarcely any trace of the original lobular 

 division remains, yet the separation of the 

 lobules, so far as their vessels are concerned, 

 remains as complete as it is in the perma- 

 nently lobular kidney of the porpoise. When 

 an injection is thrown into the vessels of one 

 lobule, that lobule only is injected, without the 

 transfer of the injection through anastomosing 

 vessels to neighbouring lobules. Obstruction 

 of the artery passing to one lobule will effec- 

 tually prevent the injection of that lobule, 

 while the surrounding parts are completely 

 injected. It occasionally happens during life 

 that the vessels supplying one or two lobules 

 become obstructed, and as a consequence of 

 this obstruction those lobules become atro- 

 phied while the rest of the gland is perfectly 

 nourished. Additional evidence of the com- 

 plete isolation of the lobules of the human 

 kidney is afforded by certain other patho- 

 logical conditions, which may, with advantage, 

 be briefly alluded to in this place. Fig. 147 

 represents a section of a kidney, the glan- 

 dular structure of which has been destroyed 

 by cysts developed in its substance ; the part 

 which remains is a framework or skeleton, con- 

 sisting of the capsule (a) continuous below 

 with the pelvis (6), which is much dilated, 



