858 
UKINARY CALCULI IN THE HORSE. 
of the tube. Urinary calculi are seldom single, generally they occur in 
large numbers, or as so-called gravel. 
In herbivora, urinary calculi most frequently contain triple phosphate 
and carbonate of calcium; in sheep, some have been found to consist of 
silicic acid, with phosphates of calcium and magnesium. Urinary calculi in 
herbivora are sometimes coloured red by iron salts; their surface is generally 
smooth, though those covered with oxalate of calcium are rough and uneven. 
In carnivora one distinguishes : 
(a) Uric acid calculi, which consist of phosphate and carbonate of calcium 
and of urate of ammonium. These often attain considerable size, and 
appear smooth and white on the surface. V. Batz believes they result from 
acid formation in the urine leading to deposit of calcium salts or to a basic 
condition of the urine. 
(b) Oxalic acid calculi consisting of oxalate of ammonia are usually 
coloured yellow; their surface is rough, resembling a mulberry ; Batz considers 
that oxalates are excreted when the food contains quantities of oxalic salts, 
but they may also be found in the body by the decomposition of urinary acids. 
The. excretion of oxalic acid in consequence of diseases of the organs of 
respiration and digestion, which has often been suggested, is denied by Batz. 
( c ) Cystin calculi are principally formed of cystin, are yellow, soft, and 
when dried are friable, and feel greasy to the touch. Concretions, consisting 
of epithelium mixed with lime salts and fatty crystals, are sometimes found 
in the urinary passages. As urinary calculi are of varying importance in the 
different classes of animals, and from a surgical point of view require par¬ 
ticular treatment, we shall here view them under separate heads. 
(1.) URINARY CALCULI IN THE HORSE. 
Urinary calculi rarely occur in the ureters or bladder of the horse, 
still less frequently in the comparatively wide urethra. According to 
Bang the circumference of the latter in male animals is as follows :—In 
the pelvic portion 1 to 1J inches, in the abdominal portion J to f inch, 
behind the external opening J inch. In mares the urethra is very wide, 
and calculi never remain fixed in it, and therefore in them vesical 
calculi alone claim consideration. 
Urethral calculi may be recognised in the stallion and gelding by 
difficulty in urination. The animals place themselves in position to 
urinate, but can only discharge fluid in drops or in a small stream. 
Sometimes the upper sections of the urethra are abnormally distended, 
or may be felt to contain a stone, and the catheter, when introduced, 
strikes on a hard substance. Examination per anum discovers the 
urinary bladder to be greatly over-filled, but on pressure, urine either 
fails to be discharged or issues in drops. 
Vesical calculi take longer to produce obstruction in staling; the 
urine is passed more frequently, but in small quantities, often in drops. 
When the animal has been driven fast, the fluid may be blood-stained 
on account of the stone injuring the mucous membrane. Hertwig saw 
sexual appetite excited in a mare by vesical calculus. Exploration per 
