In one extraordinary case, I found that the catheter entered a dilated seminal vesicle and failed to evacuate the bladder. This untoward occurrence must be rectified by the aid of the hand in the rectum. Usually the penetration of the bladder is signalized by the overcoming of resistance, and when the stilet is withdrawn the urine flows in a steady stream. If it fails to flow, a slight compression of the fundus of the bladder by the hand engaged in the rectum will start the stream. The catheter should be withdrawn slowly and carefully. =Catheterization in the Bovine Male.= Most veterinarians suppose that this is impossible, owing to the narrowness of the sheath interfering with the extraction of the penis, and the S shaped curve in the penis preventing the introduction of the catheter. Both obstacles can, however, be overcome in many cases. The bull may be tempted to protrude the penis by the presentation of a cow in heat, or in bull or ox the bulging anterior part of the organ may be protruded by careful manipulation through the sheath. Then the free extension of the penis can be made to efface the S shaped curve. The catheter must be small, not much over a line in caliber, and a metal stilet is employed. The animal may have to be placed under restraint, and the same antiseptic precautions are demanded as in the horse. =Catheterization in the Ram and Wether.= These must be dealt with like the bull, the only additional difficulty being in the vermiform appendix. This is small and sinuous but the longitudinal opening on its lower surface is favorable to the introduction of the catheter. =Catheterization in the Dog.= The fact that the urethra traverses the groove on the lower aspect of the bone of the penis, is held to prove an obstacle to the catheter, yet the introduction of the latter is in no sense difficult. Small or moderately sized dogs, may be held upright, the body resting on the rump and the pelvis inclined forward, which will favor the spontaneous protrusion of the penis. Or it may be pressed out by manipulation through the sheath. The catheter ⅔ ds. to 1 line in diameter may be 1¼ to 2 feet in length according to the size of the animal. It should be used aseptic. =Catheterization of the Mare.= Nothing can be easier than this operation in the mare. The shortness and dilatability of the urethra, and the accessibility of its external orifice in the center of the floor of the vulva, 4 or 5 inches in front of the lower commissure, favors the introduction of the catheter. The latter may be a foot in length, perfectly straight and it may be constructed of silver or some other metal, which may be readily boiled and rendered aseptic. In the absence of a catheter the germ free nozzle of a rectal syringe may be used, or two fingers may be passed through the urethra and parted from each other so as to allow the exit of the urine.