234 



THE CAT. 



[CHAP. vui. 



the expanded terminations of the contorted uriniferous tubes. Each 

 such corpuscle contains a bunch of minute looped capillary vessels, 

 forming what is called a cjlomcrulm (Fig. 110, h), and has itself a 

 most delicate epithelial lining contrasting with the thick spheroidal 

 lining of the uriniferous tubes. A small artery enters each glomc- 

 rulus, and there breaks up into a number of minute branches ending 

 in a capillary network, whence a small vein (Fig. Ill, <?') arises, 



Fig. 110. SEMI-DIAGRAMMATIC REPRESENTATION 

 OF A MALPIGHIAN BODY IN ITS RELATION 

 TO THE URINIFEROUS TUBE. MAGNIFIED 

 300 DIAMETERS. 



a. Capsule of the Malpigliian body continuous 

 with (&), the inembrana propria of the coiled 

 uriniferous tube. 



c. Epithelium of the Malpighian body. 



d. Epithelium of the uriniferous tube. 



e. Detached epithelium. 



f. Afferent vessel. 



g. Efferent vessel. 



li. Convoluted vessels of the glomerulus. 



Pig. 111. DIAGRAM SHOWING THE RELATION 

 OF THE MALPIGHIAN BODY TO THE URINI- 

 FEROUS DUCTS AND BLOOD-VESSELS. 



n. One of the arteries. 



a'. A branch passing to the glomerulus. 



e. Capsule of the Malpighian body. 



t. Uriniferous tubes. 



e', e'. Efferent vessels, which subdivide in the 

 plexus (p), surrounding the tube, and finally 

 terminate in the branch of the renal vein (c). 



which leaves the glomerulus, and breaks up into another network 

 or plexus (Fig. Ill, p) of capillaries surrounding the tubules, 

 whence arise other veins, which convey the blood ultimately to the 

 renal vein. Thus we have in the kidney a multitude of minute 

 special circulations, each of which is analogous to the portal system 

 or that of the coronary vessels of the heart. 



The FUNCTION of the kidney is, as has been said, to remove 

 nitrogenous waste products and salts from the blood by the secretion 

 and excretion of urine, and it thus supplements the action of the 

 lungs by the removal of matters which escape the action of the 

 pulmonary organs. The blood comes, as wo have seen, to the 

 kidneys direct from the abdominal aorta, and is therefore as pure 

 as when it leaves the left ventricle. In circulating through the 

 kidney it is still further purified, namely, from its nitrogenous waste 

 matters, and it also loses more carbonic acid by the formation of 

 urine, than it acquires by any wear and tear of the tissues of the 

 gland. Thus the blood which leaves the kidney is at its maximum 



