DISEASES OF THE URINARY SYSTEM. 267 



The blood-vessels are distended with blood. In chronic 

 nephritis supervening on the acute variety, the appearances 

 may differ but little from the above, except in the great 

 paleness of the cortex. In all long-standing cases the inter- 

 stitial-tissue becomes more involved in the pathological 

 change. It first becomes increased in amount, and after- 

 wards contracting, leads to contraction and atrophy of the 

 kidney. 



In acute pyelitis there is redness, swelling, and ecchy- 

 mosis of the lining mucous membrane, and a discharge of 

 mucus and pus. 



In chronic pyelitis the mucous lining is thickened, and 

 the pelvis is dilated and may be filled with pus, which is 

 due to the irritation caused by one or more calculi. Abscesses 

 are sometimes found in the cortex of the kidney as the 

 result of pyelitis. They may also be formed as the result of 

 chronic inflammation of the kidney itself, or from an 

 injury. 



Treatment. — In acute nephritis caused by cold, fatigue, 

 or exhaustion, if the pulse be strong, bleeding is very 

 beneficial. Those cases, however, supervening various 

 fevers, or due to injury, do not bear depletion so well. 



The bowels should be freely acted upon by the adminis- 

 tration of some purgative. Aloes is perhaps the best 

 cathartic in the horse. Oil is not so reliable. The 

 looseness of the bowels should be kept up by the adminis- 

 tration of saline purgatives, such as sulphate of sodium, or 

 sulphate of magnesium, which may be given in the water. 

 Some authors recommend the administration of opium, if 

 the pain be great, but this remedy is best withheld in the 

 treatment of nephritis. 



The pain may be relieved by the application of woollen 

 cloths wrung from hot water, or of linseed-meal poultices 

 over the loins. 



