STRUCTURE AND FUNCTION OF THE KIDNEYS. 



357 



clear as well as of the intra-cellular network of fibres, of which the ver- 

 tical rods are most conspicuous parts. 



Heidenhain observed that indigo-sulphate of sodium, and other pig- 

 ments injected into the jugular vein of an animal, were apparently ex- 

 creted by the cells which possessed these rods, and therefore concluded 

 that the pigment passes through the cells, rods, and nucleus themselves. 

 Klein, however, believes that the pigment passes through the intercellu- 

 lar substances, and not through the cells. 



In some places, it is stated that a distinct membrane of flattened 

 cells can be made out lining the lumen of the tubes (centrotubular mem- 

 brane). 



Blood-supply. In connection with the general distribution of blood- 

 vessels to the kidney, the Malpighian Corpuscles may be further consid- 



Fio. 246. 



FIG. 247. 



FIG. 246. Transverse section of a renal papilla; a, larger tubes or papillary ducts; 6, smaller 

 tubes of Henle; c, blood-vessels, distinguished by their flatter epithelium; d, nuclei of the stroma 

 (Kulliker). X300. 



FIG. 247. Diagram showing the relation of the Malpighian body to the uriniferous ducts and 

 blood-vessels, a, one of the interlobular arteries; a', afferent artery passing into the glomerulus; 

 c, capsule of the Malpighian body, forming the termination of and continuous with t, the uriniferous 

 tube; 2, 2, efferent vessels which subdivide in the plexus, p, surrounding the tube and finally ter- 

 minate in the branch of the renal vein v (after Bowman). 



ered. They (Fig. 247) are found only in the cortical part of the kid- 

 ney, and are confined to the central part, which, however, makes up 

 about seven-eighths of the whole cortex. On a section of the organ, 

 some of them are just visible to the naked eye as minute red points; 

 others are too small to be thus seen. Their average diameter is about 

 T fg- of an inch. Each of them is composed, as we have seen above, of 

 the dilated extremity of an uriniferous tube, or Malpighian capsule, 

 which incloses a tuft of blood-vessels. 



The renal artery divides into several branches, which, passing in at 

 the hilus of the kidney, and covered by a fine sheath of areolar tissue 

 derived from the capule, enter the substance of the organ chiefly in the 



