Earthy basis, nucleus, stratification, in cæcum or colon, multiple, size, number up to 1000. Composition, phosphates of lime, magnesia, and ammonia, silica, mucus, epithelium, organic matter. Ammonio-magnesian tend to crystalline form, common phosphate of lime to smooth forms. Concretions. Source in food. Ammonia from bacteridian fermentation, action of colloids, varied nuclei, rapid growth. Lesions: catarrh, dilation, obstruction, rupture, peritonitis. Symptoms: intermittent colics with obstruction, tympany, bowel distension, liquid and gaseous, before obstruction. Diagnosis: by hand in rectum, hard obstruction with distension in front. Treatment: purgative dangerous, but exceptionally successful, extraction, oleaginous enemata, laparotomy. =Horse.= Intestinal calculi have an earthy basis (ammonio-magnesian phosphate, or oxalate of lime, and more or less silica) glued together by mucus and having a central nucleus usually of some foreign body, (a particle of sand, pebble, morsel of hair, lead, cloth, nail, coin, blood clot, or inspissated mucus) around which the earthy salts have been deposited layer after layer. They are usually formed in the cæcum or double colon and may be multiple and moulded upon each other, so that they become discoid, angular or otherwise altered from the globular shape. The worn, flattened surface in such cases shows concentric rings representing the layers as deposited in succession. The _size_ of the masses may be from a pea or smaller, up to calculi of six inches in diameter. In _number_ there may be a single calculus or there may be an indefinite quantity. Zundel counted 400 in a single colon, and Gurlt 1,000. _Composition._ They are usually composed of phosphate of lime and of magnesia, of ammonio-magnesian phosphate, with a little silica, mucus, epithelium, and organic matters from the ingesta. Traces of sodium chloride, and iron oxide may also be present. The phosphates of lime, magnesia, and of ammonia and magnesia usually constitute the main part of the calculus. Fürstenberg found specimens in which the ammonio-magnesian phosphate amounted to 72 to 94 per cent. The calculi containing an excess of ammonio-magnesian phosphate tend to assume a crystalline or coralline form which causes them to be specially irritating to the mucosa. When broken they show a radiated structure from the centre to the circumference in addition to the concentric rings. These are usually of a yellowish brown or a gray color and have a specific gravity of 1694 to 1706. Calculi in which the common phosphate of lime abounds are likely to be smooth on the surface and on section show the concentric rings more distinctly and the radiating lines less so. The brownish calculi of this variety are much more compact, and harder than the crystalline or mulberry calculi, and have a higher specific gravity—(1823).