STRUCTURE OF THE KIDNEY. 



193 



The uriniferous tubules begin in the cortical part of the organ in 

 dilatations, each inclosing a tuft or glomerulus of convoluted capillary 

 blood-vessels (corpuscles of Malpighi), the dilated commencement of 



FlG. 226. DlAGEAM OF THE CURVE OF THE TUBULES IN A UNIPYBAMIDAL KIDNEY, 

 SUCH AS THAT OF THE RABBIT. (Toldt.) 



a, Malpighian bodies ; 6, first convoluted tubule ; c, d, looped tube of Henle ; e, second 

 convoluted ; /, collecting tube ; g, ducts of Bellini. 



the tubule being known as the capsule (fig. 227, 1). The tubule leaves 

 the capsule by a neck (2), which is sometimes narrowed, and in some 

 animals (e.g. frog) is long, and has ciliated epithelium ; the tubule is at 

 first convoluted (first convoluted tubule, 3), but soon becomes nearly 

 straight or slightly spiral only (spiral tubule, 4), and then, rapidly 

 narrowing, passes down into the medulla towards the dilated com- 

 mencement of the ureter as the descending tubule of Henle (5). It does 

 not at once, however, open into the pelvis of the kidney, but before 

 reaching the end of the papilla it turns round in the form of a loop 

 (loop of Henle, 6) and passes upwards again towards the cortex, parallel 

 to its former course and at first somewhat larger than before, but 

 afterwards diminishing in size (ascending tubule of Henle, 7, 8, 9). Arrived 

 at the cortex, it approaches close to the capsule from which the tubule 

 took origin, but at a point opposite to the origin, viz. near the afferent and 

 efferent vessels of the glomerulus (Golgi). It then becomes larger and 

 irregularly zigzag (zigzag tubule, 10), and may again be somewhat con- 

 voluted (second convoluted tubule, 11), eventually, however, narrowing into 



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