| Ash of— | Silica. | Ash of— | Silica. |
|---|---|---|---|
| Per cent. | Per cent. | ||
| Wheat straw | 67.6 | Rye-grass hay | 64.57 |
| Oats and husk | 38.6 | Wheat chaff | 81.2 |
| Oat straw | 35.4 | Oat chaff | 59.9 |
| Barley straw | 73.1 | Barley awn | 70.7 |
| Rye straw | 64.4 |
It is only soluble silica that is taken up into the system, and it is in this form (usually as silicate of potash or soda) that it enters the urine, but all that is wanted to precipitate it in crystalline form as a gritty sand is the presence of oxalic or other acid having a stronger affinity for its base (potash or soda).
Other conditions, however, enter largely into the causation of stone, or gravel. A high density of urine resulting from a highly saturated condition is often present for a length of time without any precipitation of solid materials. Urea and carbonates may be present in excess, the feed may be given dry, and drinking water may be deficient in quantity without any deposition of stone or gravel. In such cases, the presence of noncrystalline organic matter in the urine becomes an exciting cause. Rainey and Ord have shown experimentally that colloid (noncrystallizable) bodies like mucus, epithelial cells, albumin, pus, blood, hyaline casts of the kidney tubes, etc., not only determine the precipitation of crystallizable salts from a strong solution, but they determine the precipitation in the form of globular masses, or minute spheres, which, by further similar accessions, become stones, or calculi, of various sizes. The salts that are deposited by mere chemical reaction without the intervention of colloids appear in the form of sharply defined angular crystals, and hence the rough, jagged crystals of oxalate of lime or ammonia-magnesium phosphate. Heat intensifies the action of the colloids in causing precipitation of the dissolved salts, so that the temperatures of the kidneys and bladder constitute favorable conditions. Colloids that are undergoing decomposition are also specially powerful, so that the presence of bacteria or fungi causing fermentation is an important factor.
In looking, therefore, for the immediate causes of urinary calculi we must accord a high place to all those conditions which determine the presence of excess of mucus, albumin, pus, blood, kidney casts, blood-coloring matter, etc., in the urine. A catarrhal inflammation of the pelvis of the kidney, of the ureter, or of the bladder, generating excess of mucus or pus; inflammation of the kidneys, causing the discharge of blood, albumin, or hyaline casts into the urinary passages; inflammation of the liver, lungs, or other distant organ, resulting in the escape of albumin in the urine; disorders of the liver or of the blood-forming functions, resulting in hematuria or hemoglobinuria; sprains or other injuries to the back, or disease of the spinal marrow, which cause the escape of blood with the urine; the presence in the bladder of a bacterial ferment, which determines the decomposition of the mucus and urea, the evolution of ammonia and the consequent destruction of the protecting cellular (epithelia) lining of the bladder, or the irritation caused by the presence of an already formed calculus, may produce the colloid or uncrystallizable body that proves so effective in the precipitation of stone or gravel. It has long been known that calculi almost invariably form around any foreign body introduced into the kidney or bladder, and I have seen a large, calculous mass surrounding a splinter of an arrow that had penetrated and broken off in the body of a deer. The explanation is now satisfactory—the foreign body carries in with it bacteria, which act as ferments upon the urine and mucus in addition to the mechanical injury caused by its presence. If such a body has been introduced through the solid tissues, there is, in addition, the presence of the blood and lymph derived from the wounded structures.
CLASSIFICATION OF URINARY CALCULI.
Urinary calculi are most conveniently divided according to the locality in which they are found. Thus we find first renal calculi, formed in the kidney ([Pl. 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 feed, water, soil, or general conditions of health. This classification affords no guide to their location or symptoms, as calculi of the same chemical composition may be formed at any part of the urinary 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. ([Pl. 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 calculi 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 supposed layers. They have a specific gravity of 2,109 to 2,351, and nearly the same chemical composition as the coralline variety. Golding 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 composition almost identical with the second variety.