120 PRACTICAL MICROSCOPY. 



THE KIDNEY. 



The kidney is as singular in structure as in function. Although 

 developed in lobular form, little trace of this 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. 85) 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 fol- 

 lowing appears: 



The kidney is invested with a fibrous capsule, which is connected 

 with the parenchyma by very delicate prolongations of its connective 

 tissue fibrillae. This capsular investment is in connection, above, 

 with the supra- renal bodies; and, on the inner border, with the ves- 

 sels, etc., which enter and leave the organ at its hilum. The ureter, 

 penetrating the areolar tissue which (containing much fat) presents 

 at the hilum, may, for clearness of description, be traced backward 

 into the kidney. This tube expands into the pelvis, and reduplica- 

 tions of its wall imperfectly divide the pelvic area into three com- 

 partments, or infundibula. 



Each infundibulum is subdivided again, imperfectly, into several 

 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 Malpighii. The pelvis is lined with a variety of transi- 

 tional or imperfectly stratified epithelium, which will be described 

 hereafter. 



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

 the ureter, pelvis, and infundibula. The artery divides into numer- 

 ous branches which are seen in the diagram passing outward, 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 indi- 

 cated in Fig. 85, a division will be manifest of an outer portion, 

 bounded by the capsule externally, of granular texture, containing 

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

 cal portion there appear a number of pyramidal masses whose apices 



