222 



Retrogressive Processes. 



In construction and chemical composition of urinary calculi a 

 large variety of substances take part ; and the concrement is rarely 

 made up of but a single chemical constituent, but usually contains 

 a number of ingredients. In horses these calculi generally contain 

 carbonates and phosphates of lime, carbonate of magnesia, traces 

 of iron and occasionally silicates ; those of the cow, sheep and goat 

 are at times rich in silicates or magnesium phosphate, but also 

 contain calcium carbonate or triple phosphate. In swine they are 

 made up either of triple phosphate or calcium and magnesium 

 carbonate and phosphate ; and oxylate concretions also occur. The 

 uroliths of carnivora are a mixture of calcium carbonate, phosphate 

 and urate, or are composed in other cases of uric acid or sodium 



» 



Fig. 36. 

 Eenal calculi from cow. 



and ammunium urates or of calcium-ammonio-magnesium-phcs- 

 phate. The tabular forms, when fresh of soft consistence and of 

 greasy, slimy appearance, are mainly made up of cystin. The 

 color of urinary concretions is given by the pigment of the urine 

 or biliary pigment ; occasionally hsematin has been found to explain 

 the existence of a black color, or carbonate of iron that of a 

 metallic bronze luster (Fiirstenberg, Pflug, Miiller, Dammann, 

 Klimmer). 



The especial causes of danger in connection with urinary calculi 

 are to be found in the disturbances of urinary flow which they 

 occasion, giving rise perhaps to urinary retention. In addition 

 these foreign bodies act as irritants to the mucous membranes in 



