244 Veterinary Medicine. 



Again the obstruction of the ureter by a calculus in the 

 pelvis which falls into the infundibuliform entrance, or a stone 

 arrested at any part of the duct (or even of the urethra) or by 

 worms, hydatids, cysts or tumors, throws back on the kidney 

 the secreted urine, which distending the pelvis and urinifer- 

 ous tubes leads to direct compression and absorption of the 

 secretory parenchyma. Direct compression of the kidney by 

 an adjacent tumor will act in a similar manner. Retention cysts 

 by their gradual increase and augmenting pressure cause ab- 

 sorption of the gland tissue. 



The blocking of individual uriniferous tubules by minute 

 calculi, which is so often seen in cattle, kept on dry feeding 

 in winter, is a cause of partial nephritis, and absorption, as 

 noted by Roll. 



A somewhat rare cause of atrophy is the diminution of the 

 blood supply by arteritis and embolism of the renal artery, or 

 by pressure of tumors on that vessel. Arteritis and blocking 

 suggests at once the possible agency of the strongylus (sclero- 

 stoma) armatus in the horse. Trasbot records a striking instance 

 of compression of the renal artery and kidney by an enormous 

 sublumbar melanoma. This occurred in an aged horse and 

 led to atrophy. 



Lesions. In cases due to productive inflammation with sclerosis 

 of the kidney, the firmness, pallor and bloodlessness of the 

 organ is a marked feature. When incised it is found to be 

 composed mainly of fibrous tissue, while the glomeruli and 

 tubuli have to a large extent disappeared. 



If there has been simple lack of circulation the kidney becomes 

 flaccid, pale and small in size. The secretory elements (glomer- 

 uli and uriniferous tubes) are first absorbed, leaving the fibrous 

 network, which tends to shrink and form a hard resistant mass. 

 In extreme cases there may be absolutely no glandular tissue left, 

 and the dense shrunken mass represents only the hyperplasia of 

 the original fibrous network. In the different successive stages 

 of this process the glomeruli and tubules become flattened, the 

 epithelial cells become granular, or contain colloid casts and re- 

 frangent elements like oil globules and finally they are repre- 

 sented by a small mass of fibrous material. 



Of all the atrophies caused by the pressure of tumors perhaps 



