URINARY CALCULI IN THE HORSE. 617 



urethral calculus generally appear suddenly and are apt to recur, 

 and why the stone is almost always found at the narrowest point 

 of the tube. In horses urinary calculi are often single, in cattle 

 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. Ratz 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. Ratz 

 considers that oxalates are excreted when the food contains quantities 

 of oxalic salts, but they may also be formed in the body by the decom- 

 position 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 Ratz. 



(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 some- 

 times 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 particular treatment, we shall here view them under 

 separate heads. 



(1.) URINARY CALCULI IN THE HORSE. 



Urinary calculi rarely occur in the ureters of the horse, still less 

 frequently in the comparatively wide urethra. According to Bang 

 the diameter of the latter in male animals is as follows : — In the 

 pelvic portion 1 to 1| inches, in the abdominal portion | to § inch, 

 behind the external opening |- 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 dribbling or 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. 



