DISEASES OF THE URINARY ORGANS. 157 
Rainey, Ord, and others furnish the explanation. They not only 
show that a colloid body, like mucus, albumen, pus, or blood, deter- 
mined the precipitation or the crystalline salts in the solution, but 
they determined the precipitation in the form of globules, or spheres, 
capable of developing by further deposits into calculi. Heat intensi- 
fies this action of the colloids, and a colloid in a state of decomposition 
is specially active. The presence, therefore, of developing fungi and 
bacteria must be looked upon as active factors in causing calculi. 
In looking, therefore, for the immediate causes of calculi we must 
consider especially all those conditions which determine the presence 
of albumen, blood, and excess of mucus, pus, etc., in the urine. Thus 
diseases of distant organs leading to albuminuria, diseases of the kid- 
neys and urinary passages causing the escape of blood or the forma- 
tion of mucus or pus, become direct causes of calculi. Foreign bodies 
of all kinds in the bladder or kidney have long been known as deter- 
‘mining causes of calculi and as forming the central nucleus. This is 
now explained by the fact that these bodies are liable to carry bac- 
teria into the passages and thus determine decomposition, and they 
are further liable to irritate the mucous membrane and become enyel- 
oped in a coating of mucus, pus, and perhaps blood. 
The fact that horses, especially on the magnesian limestones, the 
same districts in which they suffer from goiter, appear to suffer from 
calculi may be similarly explained. The unknown poison which pro- 
duces goiter presumably leads to such changes in the blood and urine 
as will furnish the colloid necessary for precipitation of the urinary 
salts in the form of calculi. 
CLASSIFICATION OF URINARY CALCULI. 
These have been named according to the place where they are 
found, renal (kidney), ureteric (ureter), vesical (bladder), urethral 
(urethra), and preputial (sheath, or prepuce). They have been 
otherwise named according to their most abundant chemical constit- 
uent, carbonate of lime, oxalate of lime, and phosphate of lime cal- 
culi. The stones formed of carbonates or phosphates are usually 
smooth on the surface, though they may be molded into the shape of 
the cavity in which they have been formed; thus those in the pelvis 
of the kidney may have two or three short branchlike prolongations, 
while those in the bladder are round, oval, or slightly flattened upon 
each other. Calculi containing oxalate of lime, on the other hand, 
have a rough, open, crystalline surface, which has gained for them 
the name of mulberry calculi, from a supposed resemblance to that 
fruit. These are usually covered with more or less mucus or blood, 
produced by the irritation of the mucous membrane by their rough 
