230 VliTI.RlNARV IWTUOLOGY. 



CALCULI. 



DEFINITION. 



ETIOLOGY. 



STRUCTURE. 



SHAPE. 



SIZE. 



NUMBER. 



COLOR. 



COMPOSITION. 



VARIETIES. 



Urinary. 



.Sat'n'iiry. 



Gastric. 



Intestinal. 



Biliary. 



Lacteal. 



Venous. 



Arterial. 



Calculi are accumulation in the liorlv cavities, of min- 

 eral matter precipitated from the body fluids, or they may 

 be mineral incrustations upon foreign substances in the body 

 cavities. The mineral deposits formed within the tissues of 

 the animal body, as calcified tubercules, etc., are calcareous in- 

 filtration or tissue petrification. Calculi, however, may and 

 frequently do. become attached to the tissue, surrounding them 

 (phleboliths) , and a calcified tissue majr become separated from 

 the surrounding structures (calcified necrotic tissue in fistula). 

 Hence the two conditions, calculus formation and calcification, 

 approximate each other closelv and at times are not separable. 

 Etiology. — The causes of calculus formation are not thor- 

 oughlv understood. The most probable cause is the supersatur- 

 ation of the body fluids with salines. The fluids may become 

 super-saturated either bv an excessive production of the salines 

 or diminished excretion of them. The lack of oxj'gen or an 

 excess of carbon dioxide mav cause the precipitation in body 

 fluids, especially of calcium and magnesium carbonates. Fer- 

 mentation of various juices mav result in precipitation of a vari- 

 ety of compounds. But wliv the precipitate should accumulate as 

 a calculus is unexplained. It is a phenomenon Dot understood. 

 There are manv predisposing causes that aid in the formation of 

 calculi. The retention or delay in the excretion of fluids, especi- 

 allv if they undergo any chemical change, are principal factors in 

 calcular formation. Intoxication from mercurv predisposes to the 

 formation of urinary calculi. The presence of any foreign body, 

 as particles of sand, descpiamated cells, coagulated albumen, 

 parasites, etc., upon which a precipitate may accumulate, is a 

 predisposing cause. According to Ziegler all calculi have an 



