URINARY CALCULI. 439 



calculi of uric acid and the urates vary from a yellow to a 

 reddish-yellow or brown ; calculi of oxalate of lime are yellow, 

 yellowish-brown, brownish-green, or blackish- green. Calculi 

 of uric oxide are of a cinnamon-yellow colour, and those of 

 cystin of a yellow tint. In size and weight they present, as 

 might be supposed, the greatest variety; their specific gravity 

 varies from 1-213 to 1'975. Calculi of oxalate of lime exhibit 

 the greatest density, those which consist of the earthy phos- 

 phates, and especially of ammoniaco-magnesian phosphate, are 

 the lightest. 



With respect to absolute weight, urinary concretions may 

 vary from one or two grains (when they merely form gravel) to 

 several ounces. Some cases of enormous and almost incredible 

 size are related : Morand describes a stone in his possession 

 weighing 6 pounds and 3 ounces, Lister describes a stone of 

 51, and Earle one of 44 ounces; the latter was 16 inches in cir- 

 cumference. With regard to the number of calculi that may 

 occur in the same person, we may mention that Murat found 

 678 in the bladder of an old man, and nearly 10,000 in his 

 kidneys. Buffon's bladder contained 59 calculi. When several 

 calculi exist in the bladder their form becomes modified, and 

 they are usually more or less flattened by mutual apposition 

 and friction. I am in possession of a calculus consisting of two 

 portions ; the upper is small, weighing about two ounces, tri- 

 angular, and provided with three equal convex facettes, exactly 

 fitting into the depression of the larger inferior part, which is 

 of an oval form and weighs about five ounces. There can be 

 no doubt that this peculiarity of form arose from the frequent 

 rotation of the calculi. 



The internal structure of urinary calculi is of importance ; 

 a section may exhibit either an uniform texture throughout, or 

 concentric strata arranged around a nucleus. If the calculus 

 is formed of a single ingredient, its fractured or cut surface ap- 

 pears coarse and finely granular, and sometimes presents a 

 radiating appearance, especially in uric-acid calculi : it is earthy 

 and fragile, and does not present any regular arrangement in 

 calculi of urate of ammonia : it is dense and conchoidal in 

 oxalate of lime, and crystalline in cystin. Calculi of phosphate 

 of lime, on the other hand, exhibit an almost fibrous struc- 

 ture, distinguished by parallel striae. Calculi in which ammo- 



