162 THE AMERICAN MONTHLY [June, 



to sliow the cell structure, and another one injected to 

 show the position of the vascular system, the student 

 must bring some degree of experience to bear on the 

 study before he can hope to interpret the real structure 

 of the sections which he may have before his eyes. If 

 he has, by study of such glands as those already de- 

 scribed, the salivary glands, the mucous coats of the ali- 

 mentary tube, and such comparatively easy subjects, 

 learned to recognize ducts, secreting parts of glands, 

 capillaries, arterioles, lumina, basement layers and cell 

 boundaries, he has some reason to expect to understand 

 the kidney. If he has not had this preparation, he will 

 find the kidney a poor subject on which to make his first 

 acquaintance of gland histology. 



I shall suppose that the reader of this paper has read 

 the preceeding numbers of this series and that the parts 

 of a gland are intelligible to him. I shall also suppose 

 an acquaintance with the mere anatomical facts about 

 the organ such as are given in any elementary book of 

 anatomy. That is, to say in brief, that there are two 

 kidneys, concavo-convex in form, that each receives a 

 branch " renal-artery " from the aorta and sends a ves- 

 sel, the " renal vein," to the inferior vena-cava. That 

 each also gives off a duct, the " ureter," which runs di- 

 rect to the urinary bladder. I shall also assume tlie 

 coarse structure of the organ (fig. 1), its hollow pelvis, 

 which is an expansion of the ureter; the cortical portion, 

 made up of the vascular structures and of the tubules, 

 these running radially from the pelvis to the surface, 

 and I shall attempt to picture, in detail, the structure of 

 the cells of the tubule and the situation of the vas- 

 cular supply, in such a way as to enable one possessing 

 the necessary sections to find these parts for himself. 



A word in regard to the preparation of sections will 

 not be amiss. Injections of the kidney can be made by 

 inserting: the cmnula in the dorsal aorta and forcin<i' the 



