The marsh gas varied from 16 to 39 per cent., being especially abundant in cases of abstinence. It should, therefore, be in large amount in the tympanies which accompany febrile and other chronic affections. Hydrogen sulphide was found only in traces, recognizable by blackening paper saturated with acetate of lead. Oxygen and nitrogen were in small amount and were attributed to air swallowed with the food. In the work of fermentation the oxygen may be entirely used up. _Lesions._ These are in the main the result of compression of the different organs, by the overdistended rumen. Rupture of the rumen is frequent. The abdominal organs are generally bloodless, the liver and spleen shrunken and pale, though sometimes the seat of congestion or even hemorrhage. Ecchymoses are common on the peritoneum. The right heart and lungs are gorged with black blood, clotted loosely, and reddening on exposure. The right auricle has been found ruptured. Pleura, pericardium and endocardium are ecchymotic. The capillary system of the skin, and of the brain and its membranes, is engorged, with, in some instances, serous extravasations. _Prevention._ This would demand the avoidance or correction of all those conditions which contribute to tympany. In fevers and extensive inflammations, when rumination is suspended, the diet should be restricted in quantity and of materials that are easily digested (well boiled gruels, bran mashes, pulped roots, etc.,) and all bulky, fibrous and fermentescible articles must be proscribed. In weak conditions in which tympany supervenes on every meal, a careful diet may be supplemented by a course of tonics, carminatives and antiseptics such as fœungrec oxide of iron, hyposulphite of soda and common salt, equal parts, nux vomica 2 drs. to every 1 ℔. of the mixture. Dose 1 oz. daily in the food, or ½ oz. may be given with each meal. Musty grain and fodder should be carefully avoided, also mowburnt hay, an excess of green food to which the stock is unaccustomed, clover after a moderate shower, or covered with dew or hoarfrost, frosted beet, turnip, or potato tops, frosted potatoes, turnips or apples, also ryegrass, millet, corn, vetches, peas with the seeds fairly matured but not yet fully hardened. When these conditions cannot be altogether avoided, the objectionable ration should be allowed only in small amount at one time and in the case of pasturage the stock should have a fair allowance of grain or other dry feed just before they are turned out. Another precaution is to keep the stock constantly in motion so that they can only take in slowly and in small quantity the wet or otherwise dangerous aliment.