178 STUDENTS HISTOLOGY 



THE KIDNEY 



The kidney is as singular in structure as in function. Al- 

 though as originally developed it is divided into lobules, little 

 trace of this structure remains in the adult organ. 



The kidney consists, essentially, of an intricate system of 

 blood-vessel plexuses, in intimate relation with a system of urine- 

 tubes the whole supported by a small amount of connective 

 tissue. 



The accompanying drawing (Fig. 115) will serve to give an 

 idea of the gross plan or scheme of the structure remembering 

 that the illustration is only a diagram. 



On making a vertico- lateral section, on the median line, the 

 following parts are seen : 



The kidney is invested with a fibrous capsule, which is con- 

 nected with the parenchyma by very delicate prolongations of its 

 connective tissue fibrillae. This capsular investment is in con- 

 nection above with the supra -renal bodies, and, on the inner 

 border, with the vessels, etc., which enter and leave the organ 

 at its hilum. The ureter, penetrating the areolar tissue which 

 (containing much fat) surrounds the hilum, may, for clearness of 

 description, be traced backward into the kidney. This tube ex- 

 pands into the pelvis, and reduplications of its wall imperfectly 

 divide the pelvis into three compartments, or infimdibula. 



Each infundibulum is subdivided a^ain, imperfectly, into sev- 

 eral pockets or calyces; and into each calyx may be seen, peeping 

 from the kidney- substance, a papillary eminence or apex of a cone 

 the pyramids of Malpighi. The pelvis is lined with a variety 

 of transitional or imperfectly stratified epithelium, which will be 

 described hereafter. 



The blood-vessels, lymphatics, etc., pass in at the hilum, out- 

 side the ureter, pelvis, and infundibula. The artery divides into 

 numerous branches, which are seen in the diagram passing out- 

 ward, between the Malpighian pyramids. The renal vein pursues 

 much the same course, the main trunks lying side by side. 



On examining a section of the kidney, made in the direction 

 indicated in Fig. 115, a division of an outer portion will be mani- 

 fest, bounded externally by the capsule of granular texture, con- 

 taining the blood-vessels, etc. This is called the cortex. Within 



