RETRocRi'.ssivK TISSUE ciT.\xc;i-;s. 231 



organic nucleus. But it seems possible and quite prubable that 

 particles of inorganic matter are deposited upon an inorganic 

 nucleus in the formation of calculi. 



Structure. — The structure ()f calculi varies. Homogeneous 

 calculi are composed of layer upon la3-er of the same material 

 and have the same appearance throughout. Jfeterogeneous cal- 

 culi are laminated, i. e., they are composed of layers of dilTerent 

 material and appear different in the succeeding layers. Calculi 

 vary from finely granular masses (ai)pearing as though many 

 grains of sand had been fused into a mass) to lobulated masses 

 (mulberr}^ calculi) ; or they appear smooth as though they were 

 molten mineral run into forms. 



Shape. — Calculi assume all conceivable shapes. Cystic calculi 

 vary in form from spheres to jack straws, and even cf)ral like 

 bodies or stalactite calculi ha\-e been obser\'ed. Their form may 

 be determined bv their location. Thus renal calculi may assume 

 the shape of renal tubules, renal pelvic calculi the shape of the 

 renal peh'is. Intestinal calculi are usuallv more or less spherical 

 in shape. Salivary calculi are o\'oid. Calculi ma^ he faceted 

 when occurring in large numbers. 



Size. — The size of calculi varies from the finest sand-like 

 grains to enormous accimiulations. A 2'^.S-gram ( T oz.) cystic 

 calculus was removed from a Jack, h\ Dr. AlcCasey, Concordia, 

 Kansas. A "2(>()-gram (S oz.) cvstic calculus was removed from a 

 fi^'e-vear-old Jack at the Missouri Valley A'eterinary Association 

 clinic in Februar}-, 19()7. D'r. Z. C. Boyd, in 190(J, removed from 

 Steno's duct, in a horse, a salivarv calculus weighing I'^j grams 

 (4oz.). 



Number. — The number of calculi occurring in one animal is 

 quite variable. There has been a case reported in which there 

 were over .T<ki c\-stic calculi in one dog. although that is an un- 

 usual number. 



Color. — The color of calculi is determined by their composi- 

 tion. Thus biliary calculi are highly colored because of the bile 

 pigment, bilirubin and biliverdin, that they contain. Enteroliths 

 are usually colored from the intestinal contents. Arterioliths 

 and phleboliths are colored with hemoglobin or some of its 

 derivatives. Urinary calculi may be gray, brown, vellow, or 

 even red. depending upon their composition. Salivary calculi 

 may be chalk white or tinged Avith various colors. 



Composition.— A variety of chemical compounds are found 

 in the various calculi. Urinary calculi may contain cystin, xan- 

 thin, urates, oxalates, carbonates, phosphates, calcium, magnes- 

 ium,' etc. Cystin and xanthin urinary calculi are quite rare. 



