GLANDS. 463 



arrangement, and were readily discoverable by a simple lens on the sur- 

 face of the section. The parts of the kidney not involved in the deposit, 

 generally present no abnormal appearance." 



Lesions affecting chiefly the vascular system. 



Variations in the vascular condition of the kidney may, and frequently 

 do exist, totally unconnected with organic change : thus this organ, like 

 all other vascular structures, may be either in a hyperemic or anaemic 

 state ; and these conditions may effect either the entire vascular system, 

 or they may be local only, or they may involve respectively the venous or 

 arterial vessels. The veins of the kidney are disposed chiefly in two 

 situations, viz., on its surface, and in the substance of the pyramids, the 

 cortical substance containing but few veins. On the surface the larger 

 vessels follow a somewhat stelliform arrangement, while the capillaries 

 themselves form a meshwork, the meshes describing small pentagonal or 

 hexagonal spaces, in each of which a single convolution of a tube is 

 situated. The state of these vessels is subject to much variation ; they 

 may be in an anaemic condition, and scarcely visible, or they may be 

 gorged with blood ; in some instances this engorgement is general, and 

 in others it is confined to the stelliform vessels just referred to. These 

 conditions, as already observed, may be totally unconnected with dis- 

 ease ; when, however, there is great irregularity of injection, amounting 

 to marbling of the surface, and great increase in the size of the stellar 

 vessels, these are generally pathological, and result either from partial 

 obliteration of the venous network, or of the extrusion of the blood from 

 it, through over-distention of the loops of tubuli which form the inter- 

 vening pale spaces. 



" The engorgement of the capillaries and Malpighian tufts gives rise 

 to two conditions : first, a generally diffused heightened colour of the 

 cortical substance ; and second, increase and greater distinctness of the 

 vascular striae, running from the base of the pyramids to the external 

 surface. This latter species of injection often exists to a great extent, 

 without any corresponding injection of the rest of the kidney, and in 

 some instances the red points composing the striae are so much increased 

 in size as to form considerable petechiae (one line in diameter, or up- 

 wards), in which case the petechiae usually extend to the surface, oc- 

 cupying the intervening spaces of the venous polygons above mentioned. 

 This appearance was supposed by Rayer to occur from simple hyper- 

 trophy and vascular injection of the Malpighian bodies ; but Bowman *, 

 who has shown that the Malpighian bodies do not exist on the surface 

 of the kidney, has also given a better explanation of such petechiae, 

 which he holds to arise from rupture of the Malpighian tuft, with extra- 

 vasation of blood into the surrounding tubes. He argues that the 



* Philosophical Transactions, 1842. 

 p r 3 



