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, i 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 subse- 
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 
