STONY CONCRETIONS IN THE BLADDER. 77 



plained, (hat hereditary tendency should play so decided a part in the 

 formation of stone in the bladder. All the different generations of 

 one family have been observed to suffer from the same sort of stone. 

 Males are attacked by stone more frequently than females. The age 

 of childhood is by no means exempt ; indeed, children are rather liable 

 to the formation of calculi and gravel in their urinary passages. In 

 some countries, as in England, the malady is much more common than 

 in others. Drinking-water which contains lime seems to have some 

 influence in the production of stone, and the use of fermenting bever- 

 ages containing carbonic acid is quite decided, at least as to its effect 

 in producing oxalate-of-lime calculi. Any irritation which occasions 

 catarrh of the urinary passages may give rise to stone in the bladder ; 

 but it is quite enigmatical why many catarrhs last so long without 

 forming concrements, while others give rise to their formation very 

 soon. 



ANATOMICAL APPEARANCES. Urinary calculi vary in size, shape, 

 and .chemical composition. The smaller, which are usually extremely 

 numerous, we call "gravel." Their form and color depend mainly 

 upon their composition. They may be classified as follows : 



1. Stones consisting chiefly of uric acid and its salts. They are 

 round or oval ; usually of a reddish-brown color, very hard and heavy, 

 and with a smooth or nodular surface. 



2. Stones of oxalate of lime. They usually present a nodulated, 

 gland-like surface, whence their name, " mulberry calculus." They are 

 very hard, and of a dark-brown or blackish color (through the admix- 

 ture of transformed haematine). Yet some oxalate-of-lime stones are 

 small and pale, and in form bear a strong resemblance to hemp-seeds. 



6. Stones consisting of ammonio-magnesia phosphates. They are 

 of a whiter or grayer color ; have a round or oval shape ; are light in 

 weight, and are of friable, chalky consistence. 



4. Calculi of cystine. These are rare. They are usually of a yel- 

 lowish-white color. Their surface is smooth, more rarely nodular. 



5. Stones formed of xanthin, which are more rare even than the 

 cystine calculi. They are very hard, of a yellowish-red color, and usu- 

 ally have a smooth surface. 



6.. Stones, consisting of various layers and strata of diverse com- 

 position, are very common. Sometimes, the nucleus is of uric acid and 

 the outer layers of oxalate of lime ; more rarely, the contrary arrange- 

 ment obtains. The most common form of stratified calculus is that in 

 which a nucleus of uric acid or of oxalate of lime is enclosed in a hull 

 of phosphates, or in which there are several alternate layers of these 

 substances. 



Stones often lie free in the bladder, changing their position as the 



