158 DISEASES OF THE HORSE. 
surfaces. The color of calculi varies from white to yellow and deep 
brown, the shades depending mainly on the amount of the coloring 
matter of blood, bile, or urine which they may contain. 
Renal caleuli—These may consist of minute, almost microscopic, 
deposits in the uriniferous tubes in the substance of the kidney, but 
more commonly they are large masses and lodged in the pelvis. The 
larger calculi, sometimes weighing 12 to 24 ounces, are molded in the 
pelvis of the kidney into a cylindroid mass, with irregular rounded 
swellings at intervals. Some have a deep brown, rough, crystalline 
surface of oxalate of lime, while others have a smooth, pearly white 
aspect from carbonate of lime. A smaller calculus, which has been 
called coralline, is also cylindroid, with a number of brown, rough, 
crystalline oxalate of lime branches and whitish depressions of car- 
bonate. These vary in size from 15 grains to nearly 2 ounces. Less 
frequently are found masses of very hard, brownish white, rounded, 
pealike calculi. These are smoother, but on the surface crystals of 
oxalate of lime may be detected with a lens. Some renal calculi are 
formed of more distinct layers, more loosely adherent to one another, 
and contain an excess of mucus, but no oxalate of lime. Finally, a 
loose aggregation of small masses, forming a very friable calculus, 
is found of all sizes within the limits of the pelvis of the kidney. 
These, too, are in the main carbonate of lime( 84 to 88 per cent) and 
without oxalate. 
Symptoms of renal calculi are violent, colicky, pains, appearing sud- 
denly, very often in connection with exhausting work or the drawing’ 
cf specially heavy loads, and in certain cases disappearing with equal 
suddenness. The nature of the colic becomes more manifest if it is 
associated with stiffness of the back and hind limbs, frequent passage 
of urine, and, above all, the passage of gravel with the urine, espe- 
cially at the time of the access of relief. The passage of blood and ° 
pus in the urine is equally significant. If the irritation of the kid- 
ney goes on to active inflammation, then the symptoms of nephritis 
are added. 
Ureteric calculi.—These are so called because they are found in the 
passage leading from the kidney to the bladder. They are simply 
small, renal calculi which have escaped from the pelvis of the kidney 
and have become arrested in the ureter. They give rise to symptoms 
almost identical with those of renal calculi, with this difference, that 
the colicky pains, caused by the obstruction of the ureter by the 
impacted calculus, are more violent, and if the calculus passes on 
into the bladder the relief is instantaneous and complete. If the 
ureter is completely blocked for a length of time, the retained urine 
may give rise to destructive inflammation in the kidney, which may 
end in the entire absorption of that organ, leaving only a fibrous 
