614 THE LIVEE. 



tinged with various shades of yellow or brown by bile pigment. The 

 fractured surface shows a radiating crystalline structure. 



2. Of cholesterin, bile pigment, and salts of calcium and magnesium. 



FIG. 375. BILIARY CALCULI. 

 The smaller calculi show the faceted character ; the larger, cut across, show the lamellation. 



These are usually dark-colored, brown, reddish-black, or green, and may 

 be spheroidal or faceted, smooth or rough on the surface ; the fractured 

 surface is usually radiating crystalline. This is the most common form. 



3. Principally of bile pigment. Such calculi are rare, usually small, 

 very 'dark-colored, and not numerous. 



4. Of calcium carbonate. These are rare, have a nodular surface, and 

 a clear crystalline, not radiating fracture. 



Most calculi are formed around a central mass, sometimes called the 

 nucleus, which may consist of cholesterin, bile pigment, mucus, or epi- 

 thelium, or more rarely of some foreign body. Thus a dead parasite, a 

 needle, and fruit seeds may serve as nuclei. The body of the calculus 

 may be homogeneous, or lamellated, or crystalline. 



Biliary calculi in the gall bladder may produce no symptoms and be 

 discovered only after death. In the hepatic and common ducts they may 

 obstruct the flow of bile and lead to fatal jaundice; or they may pass 

 from time to time into the intestine, producing biliary colic. If they 

 are impacted in the cystic duct they may lead to dilatation of the gall 

 bladder. They may get into the duodenum by ulceration through the 

 walls of the ducts or gall bladder, or in the same way into the peritoneal 

 cavity. Gall stones which get into the intestinal cavity usually pass off 

 without doing any further injury, but very large calculi may cause oc- 

 clusion of the gut with fatal results. The role of micro-organisms in the 

 formation of gall stones has been the subject of significant studies. 1 



1 Consult Mignot, Arch. gen. 'de Medecine, 1898, t. ii., pp. 129 and 263: also CmMng, 

 Johns Hopkins Hosp. Bull., vol. x., p. 166, 1899; also Mieczkowski, Mitth. a d. Greuz- 

 geb. d. Med. u. Chir., Bd. vi., p. 307, 1900. 



