BILIARY CALCULI 377 



here, as in all other gall-stones, consists always of the calcium 

 salts of the pigments not of pure bilirubin and biliverdin 

 themselves. Considerable calcium carbonate is also usually- 

 present, particularly in the green layers of biliverdin cal- 

 cium. 



3. Common Gall-bladder Stones. The composition of this 

 form is but little different from the above, the chief difference 

 being in the structure. They present externally a firmer crust, 

 usually distinctly laminated ; in the center is a softer pigmented 

 nucleus which frequently shows a central cavity containing 

 fluid. Such calculi are not distinctly crystalline in structure, 

 and are small, seldom larger than a cherry. 



4. Mixed Bilirubin-calcium Calculi. These generally occur 

 singly, but sometimes in groups of three or four, and are of 

 large size. Although the chief constituent is bilirubin-calcium, 

 there is always much cholesterin, often over 25 per cent. 

 Copper and traces of iron may also be present. Their structure 

 is laminated, with sometimes a crystalline cholesterin nucleus. 



5. " Pure " Bilirubin-calcium Calculi. In addition to the 

 chief constituent, biliverdm-ealcium, bilifuscin, and bilihumin l 

 are practically always present. Bilihumin is at times the chief 

 ingredient, and may form over half of the substance ; bilicyanin 

 is rarely present. There is always some cholesterin, but some- 

 times only traces. These calculi are small, from the size of a 

 grain of sand to that of a pea, and they occur in two distinct 

 forms. One form is of wax -like consistence ; the other is harder, 

 steel-gray or black in color, with a metallic luster. Pure bili- 

 rubin and biliverdin, not combined with calcium, are practically 

 never present in concretions. 



6. Rarer Forms. (a) Amorphous and incompletely crystal- 

 line cholesterin gravel. Cholesterin externally giving them a 

 pearly luster ; pigment in the center. 



(6) Calcareous Stones. Consist chiefly of a mixture of cal- 

 cium carbonate and bilirubin-calcium. Calcium carbonate may 

 occur either as a superficial crust, or as small masses within an 

 ordinary calculus ; calcium sulphate and phosphate occur rarely 

 in traces. Stones consisting mainly of calcium carbonate are 

 extremely rare in man, but more frequent in cattle and other 



1 Biliverdin differs from bilirubin in containing one more atom of oxygen in 

 the molecule, and it is easily formed from bilirubin even exposure to air will 

 slowly bring about the oxidation. Bilifuscin is a still more oxidized deriva- 

 tive so much so that it does not give Gmelin's reaction (with HNO 3 + HNO 2 ) 

 for bile-pigments. Bilihumin represents the most oxidized of these products, 

 is brown in color, and is the chief constituent of the residue left after treating 

 gall-stones with ether, alcohol, and chloroform to dissolve out the cholesterin. 



