CHRONIC NEPHRITIS 393 



of the disease the kidney usually is small small white 

 kidney. 



(6) Chronic interstitial nephritis, characterized by cardio- 

 vascular changes which are pronounced, but only in a few 

 instances will dropsical conditions appear. 



Etiology. It has been observed that chronic nephritis in 

 some instances follows the acute form of the disease. This is 

 true no doubt only in the subacute or milder acute cases. 



It may develop gradually as an insidious disease without 

 any apparent cause. 



Injurious substances in the form of irritants, which may 

 be either parasitic or chemical in nature, in being eliminated 

 via the kidneys, may produce sufficient irritation to induce a 

 chronic inflammation. Certain drugs when administered 

 for some time (turpentine) or absorbed from the skin, as in 

 the treatment of mange (coal-tar compounds), will produce 

 irritation resulting in chronic nephritis. 



It may follow some of the infectious diseases, such as dis- 

 temper in the dog and cat. The excess of w r aste products 

 together with the various toxins formed are eliminated in 

 such quantity that they irritate the renal tissue. 



Subjection to extremes in temperature (cold or heat) dis- 

 turbs metabolism, which increases the action of the kidneys, 

 and the amount of albuminous decomposition may be a 

 cause. In other cases no apparent cause can be found. 



Pathology. (a) In chronic parenchymatous nephritis sev- 

 eral varieties have been recognized. 



The large white kidney is characterized by enlargement, 

 the capsule very thin. When cut longitudinally the cortex 

 is swollen and yellowish-white in color, mottled on surface 

 with a number of opaque spots. The pyramids of the kidney 

 are deeply congested. 



The small white kidney in which the connective tissue is 

 found thickened, and a gradual reduction in the enlargement 

 of the parenchymatous tissue. On cut surface the resistance 

 is much greater than the other type, the cortex is much 

 smaller and contains a number of white or whitish-yellow 

 spots. These whitish-yellow spots represent areas of fatty 

 degeneration. The interstitial tissue is changed, enlarged, 



