In urgent cases the gas must be allowed to escape without delay, and this is best accomplished by the use of the trocar. The trocar is a sharp-pointed instrument incased in a cannula or sheath, which leaves the sharp point of the trocar free. (See Pl. III, figs. _5a_ and _5b._) In selecting the point for using the trocar a spot on the left side equally distant from the last rib, the hip bone, and the transverse processes of the lumbar vertebrÊ must be chosen. Here an incision about three-fourths of an inch long should be made with a knife through the skin, and then the sharp point of the trocar, being directed downward, inward, and slightly forward, is thrust into the paunch. (Pl. I.) The cannula or sheath of the trocar should be left in the paunch so long as any gas continues to issue from it. If the cannula is removed while gas is still forming in the paunch and the left flank becomes considerably swollen, it may be necessary to insert it again. It is well, accordingly, to observe the cannula closely, and if gas is found to be issuing from it, it should not be removed. When gas issues from it in considerable quantities the sound accompanying its escape renders the exact condition obvious. It is occasionally necessary to keep the cannula in the stomach for several hours. When this is necessary a piece of stout cord should be passed round the neck of the cannula immediately below the projecting rim and then be passed round the animal's body and tied in a secure knot, and a careful attendant must remain with the cow during the entire period that the instrument is in place. The rim surrounding the mouth of the cannula should be in contact with the skin. Whenever the person in charge of the cow is convinced that gas has ceased to issue from the cannula the instrument should be removed. The trocar is to be used only in extreme or urgent cases, though everyone who has had experience in treating indigestion in cattle realizes that he has saved the lives of many animals by its prompt application. When the tympanitic animal is not distressed and the swelling of the flank is not great, or when the most distressing condition has been removed by the use of the trocar, it is best to use internal medicine. Two ounces of aromatic spirits of ammonia should be given every half hour in a quart of cold water; or half an ounce of chlorid of lime may be dissolved in a pint of tepid water and the dose repeated every half hour until the bloating has subsided; or 1 ounce of creolin in 2 quarts of tepid water may be given at one dose or carefully injected through the cannula directly into the paunch to stop fermentation and the consequent formation of gas. It is generally necessary to give a moderate dose of purgative medicine after bloating has subsided, as animals frequently show symptoms of constipation after attacks of indigestion. For this purpose 1 pound of Glauber's salt may be used.