URINARY CALCULI. 785 



amorphous and crystalline sediment in the urine on one side and urinary 

 sand or large calculi on the other to be the occurrence of an organic 

 frame in the latter. As the sediments which appear in normal acid urine 

 and in a urine alkaline through fermentation are diverse, so also are the 

 urinary calculi which appear under corresponding conditions. 



If the formation of a calculus and its further development take place 

 in an undecomposed urine, it is called a PRIMARY formation. If, on the 

 contrary, the urine has undergone alkaline fermentation and the ammonia 

 formed thereby has given rise to a calculus formation by precipitating 

 ammonium urate, triple phosphate, and earthy phosphates, then it is 

 called a SECONDARY formation. Such a formation takes place, for 

 instance, when a foreign body in the bladder produces catarrh accom- 

 panied by alkaline fermentation. 



We discriminate between the nucleus or nuclei if such can be seen 

 and the different layers of the calculus. The nucleus may be essentially 

 different in different cases, for quite frequently it consists of a foreign 

 body introduced in the bladder. The calculus may have more than 

 one nucleus. In a tabulation made by ULTZMANN of 545 cases of vesic- 

 ular calculi, the nucleus in 80.9 per cent of the cases consisted of uric 

 acid (and urates); in 5.6 per cent, of calcium oxalate; in 8.6 per cent, 

 of earthy phosphates; in 1.4 per cent, of cystine; and in 3.5 per cent, 

 of some foreign body. 



During the growth of a calculus it often happens that, for some reason 

 or other, the original calculus-forming substance is covered with another 

 layer of a different substance. A new layer of the original substance may 

 deposit on the outside of this, and this process may be repeated. In 

 this way a calculus consisting originally of a simple stone may be con- 

 verted into a so-called compound stone with several layers of different 

 substances. Such calculi are always formed when a primary is changed 

 into a secondary formation. By the continued action of an alkaline 

 urine containing pus, the primary constituents of a primary calculus 

 may be partly dissolved and be replaced by phosphates. Metamor- 

 phosed urinary calculi are formed in this way. 



Uric-acid calculi are very abundant. They are variable in size and 

 form. The size of the bladder-stone varies from that of a pea or bean to 

 that of a goose-egg. Uric acid stones are always colored; generally 

 they are grayish-yellow, yellowish-brown, or pale red-brown. The upper 

 surface is sometimes entirely even or smooth, sometimes rough or uneven. 

 Next to the oxalate calculus the uric-acid calculus is the hardest. The 

 fractured surface shows regular concentric, unequally colored layers 

 which may often be removed as shells. These calculi are formed pri- 

 marily. Layers of uric acid sometimes alternate with other layers of 

 primary formation, most frequently with layers of calcium oxalate. 



