134 DISEASES OF CATTLE. 



CLASSIFICATION OF URINARY CALCULI. 



Urinary calculi are most conveniently divided according to the local- 

 ity in which they are found. Thus we find first renal calculi, formed 

 in the kidney (PI. XI, fig. 1), and which for cattle must be again 

 divided into calculi of the uriniferous tubes and calculi of the pelvis. 

 The second class are named ureteral calculi, because they are found in 

 the duct leading from the kidney to the bladder (ureter). The third 

 class are the vesical calculi, from the bladder or vesicle in which they 

 are found. The fourth class are the urethral calculi, and are found in 

 the duct leading outward from the bladder through the penis (urethra). 

 The fifth and last class are the preputial calculi, since they are found 

 within the sheath of the penis (prepuce). 



Calculi may also be classed according to their chemical composition, 

 and this has the advantage of suggesting the special cause of each as 

 found in the food, water, soil, or general condition of health. This 

 classification affords no guide to their location or symptoms, as calculi 

 of the same chemical composition may be found at any part of the uri- 

 nary passages, as those formed in the kidney may pass on through all 

 the various passages outward, unless it is found at any point of their 

 progress that they have grown so large that the passage will not admit 

 them. The following are among the concretions found in the various 

 parts : 



(1) Coralline calculi. — These are of a dull- white color and irregular 

 surface, like coral. They are made up of hard and resistant layers 

 evenly deposited around a central nucleus. (PI. XI, fig. 3. ) Their 

 specific gravity is 1. 760, water being 1.000, and they contain 74 per cent 

 of carbonate of lime with some carbonate of magnesia, organic matter, 

 and a trace of carbonate of iron. Yellowish white, smooth, round cal- 

 culi of the same chemical composition are met with. 



(2) Pearly calculi. — These are more frequent than the first-named 

 variety. They are very hard and smooth on the surface, reflecting a 

 play of various colors after the fashion of a pearl. This peculiarity 

 appears to be caused by the thinness and semitransparency of the 

 superposed layers. They have a specific gravity of 2.109 to 2.351, and 

 nearly the same chemical composition as the coralline variety. Gold- 

 ing Bird found a specimen of this kind formed of carbonate of lime 

 and organic matter only. 



(3) Green calculi {metalloid calculi). — These are usually small and 

 numerous, as they are exceedingly common. They are of a very hard 

 consistency, and have a clear, polished, greenish surface of almost 

 metallic brilliancy. They have a specific gravity of 2.301, and a com- 

 position almost identical with the second variety. 



(i) White calculi.— Pure, white, smooth, lustrous calculi are rare. 

 They have a specific gravity of 2.307, and contain as much as 92 per 

 cent of carbonate of lime with carbonate of magnesia and organic 

 matter. 



