Always pull a piece of skin either backward or forward, before the incision is made through the integument. The reason for doing this is, because, when the trocar is removed, the skin may resume its proper place, and act as a valve, keeping out the atmosphere from the cavity; for external air, getting into the interior of the chest, is proved to be most injurious to life. There is to be tendered but one last admonition even this has been in a great measure anticipated by the previous observations. The animal must not be left during the operation. Whatever time may be consumed by the withdrawal of the liquid, the operator must remain a patient spectator of the slow abstraction; for if the horse should be left, syncope may come on during such absence, and the animal, on the person's return, be found prostrate upon the ground. On the first sign of weakness, the cannula should be at once removed; for, should it be suffered to remain, regardless of this caution, the horse may even die through sudden collapse. The treatment, after the withdrawal of the fluid, is entirely changed; pleurisy has now departed, and weakness is left behind. The most nourishing but carefully-prepared food must be given; boiled oats and beans may be allowed in any quantity which the animal will consume, while the following ball should be administered, night and morning:-- Iodide of iron One drachm. Strychnia Half a grain. Sulphate of zinc Half a drachm. Extract of gentian and powdered quassia Of each a sufficiency. That which will denote a fatal termination is restlessness; neighing; partial sweats; swellings under the region of the chest, and a distressed breathing, which nothing can relieve. The death struggle is as short as the disease has been painful. DISEASE OF THE HEART. This affection is characterized by various names in scientific books, as carditis, pericarditis, hydrops pericardii, inflammation of the pericardium, etc. All such conditions in the horse were discovered by examinations instituted after death, when, unfortunately, all opportunity of observing the symptoms had ceased. Veterinary science cannot distinguish one state from another, while life exists. Probably this deficiency may be attributed to the inutility of such discrimination. =Disease of the heart= in horses is incurable. In man, who can strictly conform to his physician's orders; avoid excitement; abstain from exertion; eat only such a quantity of such a food, prepared after such a manner; feed at such an hour and rest at such a time; who can live by rule;--in man, the diseases of the heart are only to be delayed, not driven from their certain issues. [Illustration: DISEASE OF THE HEART IN THE HORSE.]