The way to ascertain the presence of cystic calculus is to make an examination per rectum. Make the investigation with all gentleness. The foreign body may then be distinctly felt; even its size, form, and irregularities can by this means be discovered. Urethral calculus is a small stone which, during the flow of urine, has been carried out of the bladder and is spasmodically grasped by the muscle of the urethra. The passage is effectually closed and great suffering is induced. Should the stone be impacted within the exposed part of the canal, the precise situation is easily told. Behind the stoppage the passage is distended by fluid; while before it all is natural. The calculus should be cut down and removed; the wound being afterward dressed with a solution of chloride of zinc--one grain to the ounce of water. This is an easy and by no means a dangerous operation. Any person of ordinary skill having a sharp knife may undertake it. For renal calculus little can be done. That little, however, consists in mingling two drachms of hydrochloric acid with every pail of water, and allowing the animal to imbibe as much as it pleases. Should the medicated drink be refused, the horse must be starved into accepting it. With this liquid, however, the stone must be small to be dissolved; but it effectually checks the further increase of the calculus. =Lithotomy= is the name given to that operation by which large stones are removed from the bladder of the horse. It is far too complicated and too serious a proceeding to be entrusted to any general reader. No direction which possibly could be misconstrued shall, therefore, be attempted. When an operation is required for stone in the bladder, a qualified veterinary surgeon had better be employed. Mr. Simmonds, of the Royal Veterinary College, Camden Town, however, deserves praise for having invented an instrument by means of which stone can generally be removed from the bladder of the mare without resort to the knife being necessary. HEMATURIA, OR BLOODY URINE. The name fully characterizes this affection. The blood emitted may consist of small clots; it may congeal after it has left the body; or it may be entirely mingled with--giving a brownish tinge to--the water. Upon the exhibition of this disorder, always treat the symptoms first; when all chance of immediate danger has disappeared, examine the body to ascertain whence the hemorrhage proceeded, because in this affection the symptoms really constitute the disease; and when the first has disappeared, the last is cured. [Illustration: A HORSE SUFFERING FROM HEMATURIA, OR BLOODY URINE.]