DISEASES OF THE URINARY ORGANS. 161 



tepid water or to insert a sound or catheter to furnish a guide upon 

 which the incision may be made, and in case of a large stone it may 

 be needful to enlarge the passage by cutting in a direction upward 

 and outward with a probe-pointed knife, the back of which is slid 

 along in the groove of a director until it enters the bladder. 



The horse may be operated upon in the standing position, being 

 simply pressed against the wall by a pole passed from before back- 

 ward along the other side of the body. The tepid water is injected 

 into the end of the' penis until it is felt to fluctuate under the pressure 

 of the finger, in the median line over the bone just beneath the anus. 

 The incision is then made into the center of the fluctuating canal, and 

 from above downward. When a sound or catheter is used as a guide 

 it is inserted through the penis until it can be felt through the skin 

 at the point where the incision is to be made beneath the anus. The 

 skin is then rendered tense by the thumb and fingers of the left hand 

 pressing on the two sides of the sound, while the right hand, armed 

 with a scalpel, cuts downward onto the catheter. This vertical in- 

 cision into the canal should escape wounding any important blood 

 vessel. It is in making the obliquely lateral incision in the subser 

 quent dilatation of the urethra and neck of the bladder that such 

 danger is to be apprehended. 



If the stone is too large to be extracted through the urethra, it may 

 be broken down with the lithotrite.and extracted piecemeal with the 

 forceps. The lithotrite is an instrument composed of a straight stem 

 bent for an inch or more to one side at its free end so as to form an 

 obtuse angle, and having on the same side a sliding bar moving in a 

 groove in the stem and operated by a screw so that the stone may be 

 seized between the two blades at its free extremity and crushed again 

 and again into pieces small enough to extract. Extra care is required 

 to avoid injury to the urethra in the extraction of the angular frag- 

 ments, 'and the gravel or powder that can not be removed in this way 

 must be washed out, as advised below. 



When a pultaceous magma of carbonate of lime accumulates in the 

 bladder it must be washed out by injecting water through a catheter 

 by means of a force pump or a funnel, shaking it up with the hand 

 introduced through the rectum and allowing the muddy liquid to flow 

 out through the tube. This is to be repeated until the bladder is 

 empty and the water come away clear. A catheter with a double 

 tube is sometimes used, the injection passing in through the one tube 

 and escaping through the other. The advantage is more apparent 

 than real, however, as the retention of the water until the magma has 

 been shaken up and mixed with it hastens greatly its complete 

 evacuation. 



36444°— 16 11 



