LYMPHATICS, NERVES, CONNECTIVE-TISSUE. 



391 



arterial trunks, or from those efferent vessels (e) which lie next to the medulla. The latter are 

 said to be devoid of muscle. According to Huschke, a few vasa recta are formed by the union 

 of the capillaries of the medullary rays. All the vasa recta enter the boundary la) r er, where 

 they split up into a leash or pencil of small arterioles, which pass between the straight tubules 

 towards the pelvis, and form in their course a capillary network with elongated meshes. From 

 these capillaries there arise venous radicles, which, as they proceed towards the limit between 

 the cortex and medulla, form the venae rectae (c), and open into the concave side of the venous 

 trunks in this region. At the apex of the papillae, the capillaries of the medulla form connec- 

 tions with the rosette-like capillaries surrounding the excretory ducts (at 1). 



[The circulation through the vasa recta is most important. The cortical system of blood- 

 vessels communicates with the medullary, but as most of the vasa recta are derived from the 

 same vessel as the interlobular arteries, it is evident that they may form a side stream through 

 which much of the blood may pass without traversing the vessels of the cortex. Very probably 

 the " short-cut " is useful in congestions of the kidney. The amount of distention of these 

 vessels also will influence the size of the tubules lying between them. There are two other 

 channels by which blood can pass through the renal arteries without traversing the glomeruli 

 (1) The anastomoses between the terminal twigs of the renal artery and the subcapsular venous 

 plexus ; (2) small branches given off, either by the interlobular arteries or by the afferent 

 vessels before entering the glomeruli (Brunton).] 



The blood-vessels of the external capsule are derived partly from the terminal twigs of the 

 interlobular arteries, partly from branches of the supra-renal, phrenic, and lumbar arteries, 

 which anastomose with each other. The capillary network has simple meshes. The venous 

 radicles pass partly into the vena3 stellatse, and partly into the veins of the same name as the 

 arteries. The connection of the area of the renal artery with the other arteries of the capsule 

 explains why, after ligature of the renal artery within the kidney, the blood still cir- 

 culates in the external capsule (C. Ludivig, M. Herrmann) \ in fact, these blood-vessels still 

 supply the kidney with a small amount of blood, which may suffice to permit a slight secretion 

 of urine to take place (Litten, Pautynski). 



HI. The lymphatics form a wide-meshed plexus in the capsule of the kidney, while under it 

 they form large spaces (Heidenhain). In the parenchyma of the kidney, the lymphatics are said 

 to be represented by large slits devoid of a wall in the tissues, and are more numerous around the 

 convoluted than the straight tubules. The slits pass to the surface of the kidney, and expand 

 under the capsule. When the lymphatics are greatly distended, they tend to compress the 

 uriniferous tubules and the blood-vessels (C. Ludivig and Zawarykin). According to Ryndowsky, 

 the uriniferous tubules are surrounded by true lymphatics with an endothelial lining, and they 

 even penetrate into the capsule of Bowman along with the vas afferens. [The large blood- 

 vessels are also surrounded by 

 lymphatics.] Large lymphatics, 

 provided with valves, pass out of 

 the kidneys at the hilum, while 

 others emerge through the cap- 

 sule ; both sets are connected 

 with the lymph-spaces of the cap- 

 sule of the kidney (A. Budge). 



IV. The nerves form small 

 trunks provided with ganglia, 

 and accompany the blood-vessels. 

 [They are derived from the renal 

 plexus and the lesser splanchnic 

 nerve. ] They contain medullated 

 and non-medullated fibres, and 

 the latter have been traced by 

 W. Krause as far as the apices of 

 the papilla?. Their mode of ter- 

 mination is unknown. Physio- 

 logically, we are certain that they 

 contain both vaso-motor and sen- 

 sory fibres ; perhaps there may 

 be also vaso-dilator and secretory 

 fibres. 



V. The connective-tissue, or -p- 247 

 interlobular stroma, forms in the m . ,. ,, ?\ti"--l- j 

 papillaB, especially at their apices, Transverse section of apex of Malpighian pyramid, 

 fibrous, concentric layers of con- collecting tubes ; b, c, d, tubules of Henle ; e, 

 siderable thickness between the ca P manes - 



excretory tubules (fig. 247). Farther outwards, the fibrillar character becomes less distinct, 

 while at the same time branched connective-tissue corpuscles occur in greater numbers. In the 



f, 



a, large 

 blood- 



