“3. I use the trochar after three or four weeks of ineffectual treatment, without any absorption being produced. “4. In chronic idiopathic hydrothorax, a latent pleurisy with simply physical signs to indicate _extensive_ effusion, but when the rational signs are either very slight or none at all save a general malaise and weakness.” The use of iodide of potassium and vegetable and mineral tonics must be perseveringly employed and the strength further supported by a generous diet, to secure the animal against the dangers of extreme prostration, of suppuration, or other undesirable conditions of the exuded product. Among the dangers attending thoracentesis are fainting as a result of shock on the sudden withdrawal of so much liquid, rupture of the false membranes, and even of the enclosed lung tissue or of blood vessels, under the sudden expansion of the partially collapsed lung confined by the investing false membrane, and the introduction of pus or septic germs into the pleural cavity. To obviate the first named dangers tight bands (circingles) around the chest will give support and limit sudden expansion. In case of excess of liquid the withdrawal of one-half or two-thirds at a time will allow opportunity for accommodation. Hæmorrhage may be met by the internal use of chloride, sulphate or nitrate of iron, matico, hamamelis or tannic acid, and a weak solution of boric acid or other antiseptic agent may even be injected in small amount into the pleural cavity. In obstinate and chronic cases the injection of a weak solution of iodine and iodide of potassium is often of service. In other cases a normal chloride of sodium solution (previously sterilized) may be introduced as soon as a partial evacuation causes uneasiness, and by a succession of such evacuations and injections the residuum liquid may be rendered clear and largely aseptic on a single occasion. In the smaller animals the selection of the most dependent part for insertion of the trochar is not so essential, as the body may be turned to facilitate the drainage. On completion of the operation the wound may be again treated antiseptically and coated with aristol or collodion. PNEUMOTHORAX. AIR OR GAS IN THE PLEURA. Causes, decomposition of liquid effusion, perforation from a bronchium, the stomach, a thoracic wound. Symptoms, metallic tinkling, splashing, succussion, drum-like resonance, suppressed respiratory murmur, distance of cough sound, distress, anxiety, dyspnœa, bulging intercostal spaces, sometimes a wound. Treatment, closure of wound, calmatives, aspiration of gas. Treatment for pleurisy.