102 DISEASES OP THE HOESE. 



vessel. It is in making the obliquely lateral incision in the subse- 

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

 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 hajid 

 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 comes away clear. A catheter with a double 

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

 and escaping through the other. But the advantage is more ap- 

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

 been shaken up and mixed with it hastens greatly its complete evacu- 

 ation. 



To prevent the formation of a new deposit any fault in feeding 

 (dry grain and hay with privation of water, excess of beans, pease, 

 wheat bran, etc.) and disorders of stomach, liver, and lungs must 

 be corrected. Give abundance of soft drinking water, encouraging 

 the animal to drink by a handful of salt daily ; let the food be laxa- 

 tive, consisting largely of roots, apples, pumpkins, ensilage, and give 

 daily in the drinking water a dram of carbonate of potash or soda. 

 Powdered gentian root (3 drams daily) will also serve to restore the 

 tone of the stomach and system at large. 



Urethral calculus {stone in the urethra). — This is less frequent in 

 horses than in cattle and sheep, owing to the larger size of the urethra 

 in the horse and the absence of the S-shaped curve and vermiform 

 appendix. The calculi arrested in the urethra are never formed 

 there, but consist of cystic calculi which have been small enough to 

 pass through the neck of the bladder, but too large to pass through 

 the whole length of the urethra and escape. Such calculi therefore 

 are primarily formed either in the bladder or kidney, and have the 

 chemical composition of the other calculi found in those organs. 

 They may be arrested at any point of the urethra, from the neck of 

 the bladder back to the bend of the tube beneath the anus, and from 



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