186 SWINE PRACTICE 



supporting framework, is caused primarily by relatively mild ir- 

 ritants acting over a long period of time. These cases have not 

 been recognized clinically, but by tracing the swine that show the 

 lesions when slaughtered it is usually found that the feed of the 

 animals has been at fault. In some cases parasites and calculi are 

 responsible for the condition. 



Lesions. — Chronic parenchymatous nephritic kidneys are enlarged. 

 The capsule is not easily removed, and when pealed off small frag- 

 ments of kidney tissue remain attached to it. The kidney is mottled, 

 due to hemorrhages and infarction, and there is no definite line of 

 demarcation between the medulla and cortex. Microscopically the 

 parenchymatous cells are found enlarged and cloudy, but tube casts 

 are rarely observed. 



Chronic interstitial nephritis is characterized by fibrous pro- 

 liferation. The newly formed fibrous tissue may or may not cicatrize. 

 The gross appearance of the kidney varies according to the amount 

 and disposition of fibrous tissue. If the condition is localized accord- 

 ing to the distribution of small arteries the fibrous tissue will occur 

 in foci, and spotted kidney is the result, the white spot being masses 

 of fibrous tissue. If this fibrous tissue is uniformly deposited 

 throughout the kidney and does not cicatrize, the kidney is enlarged, 

 dense, and hard — one of the types of the large white kidney. Granu- 

 lar kidneys are the result of the proliferation, and later cicatrization, 

 of fibrous tissue in and around the glomeruli or tubules. Granular 

 kidneys have rough, small projections thickly studded over the sur- 

 face; such kidneys are usually of a red color. The extensive pro- 

 liferation and cicatrization of fibrous tissue in all the cortical sub- 

 stance, when associated with a thickening of the capsule, produce 

 the small, hard, or sclerotic kidney. Microscopically excessive quanti- 

 ties of fibrous tissue are found, and the parenchymatous tissue is 

 diminished, due to pressure atrophy. Sometimes there may be large 

 areas of fibrous tissue in which no parenchymatous tissue appears 

 or only remnants of tubules or glomeruli. 



Symptoms. — Records of the clinical evidence of chronic interstitial 

 nephritis in swine are wanting. Swine with extensive kidney lesions 

 are usually in fair condition when they are observed at the time of 

 slaughter. 



Treatment. — The application of therapeutic agents for the relief of 

 chronic interstitial nephritis in swine has not been practiced. Should 



