2IO 



NORMAL HISTOLOGY. 



continuous around the narrow stalk, through which the vessels pass and at which the 

 reflection of the capsule is incomplete. The inner (" visceral ") layer is firmly attached 

 to the glomerulus by delicate strands of connective tissue which likewise hold together 

 the capillaries. The capsule consists of a membrana propria lined with a single layer 



Blood-vessel 



FIG. 259. Convoluted tubules, cut 

 transversely and obliquely, showing 

 character of epithelial lining. X 280. 



FIG. 260. Portion of medullary ray, showing "spiral" part 

 of convoluted and collecting tubules. X 280. 



of flat polyhedral epithelial cells, directly continuous with the epithelium of the tubule. 



2. The proximal convoluted tubule begins at the constriction, the neck, of the 



capsule and abruptly widens into the tortuous segment that forms approximately 



one fifth of the entire length of the tubule. Its diameter varies from 40-60 n. 



Blood-vesse 



Loo 



FIG. 261. Longitudinal section of 

 medulla, showing parts of limbs of 

 Henle's loop. X 280. 



Collecting tubule 



FIG. 262. Longitudinal section of medulla 

 passing through Henle's loop. X 280. 



In common with other parts of the renal tubule, its wall consists of a homogeneous 

 basement membrane lined with a single layer of epithelial cells. The latter, in the 

 convoluted tubule, are not defined by sharp outlines, but more or less blended into 

 a continuous protoplasmic sheet, a form of syncytium, in which the spherical nuclei, 

 which lie near the basement membrane, indicate the approximate extent of the 

 individual low columnar cells. Although subject to much and inconstant variation, 

 their cytoplasm exhibits a differentiation into a broad darker outer and a narrow 



