A patient suffering from intestinal obstruction, or from generalised peritonitis has his stomach and intestines full of highly infective fluid. Reverse peristaltic may set in merely as the result of the inhalation, or later from handling the contents of the abdomen, and the feculent fluid gushes up the œsophagus with little or no warning. Since vomiting in these cases may occur even in deep anæsthesia, when the cough reflex which is the normal sentry to the entrance of the larynx, is abolished, the dangers of insufflation are very real indeed. Personally, the author prefers to wash out the stomach before beginning to induce anæsthesia in these cases, but some surgeons believe that the shock of this procedure outweighs the advantages. SYMPTOMS AND TREATMENT OF VOMITING. In ordinary cases, vomiting is usually heralded by a definite train of symptoms. Respiration becomes shallow, the colour a little pale and the pulse rather small. The pupil dilates, but remains active to light, indicating that the alteration of respiration and circulation is not due to overdose. At the first appearance of such symptoms, a brisk rub of the lips and thereafter an increase of the vapour strength of the anæsthetic will often avert the impending vomiting by deepening the anæsthesia, but if the possibility of this complication has occurred to the anæsthetist too late for its prevention, the head must be turned well to one side, and the other shoulder slightly elevated by a pillow, so that vomited material will fall out of the mouth at once. When the actual act of vomiting is over, no time must be lost in mopping out the mouth and pressing on with the production of a deeper anæsthesia. (B) Respiratory Dangers. These divide themselves into two groups:-- (1) MECHANICAL.--The respiratory movements continue, but the ingress and egress of air is blocked. _The symptoms and preventative treatment_ have been referred to at some length in Chapter III., and no further account of these is therefore necessary. _The treatment of a complete blockage_ of the air passages which resist the measure there described, alone remain to be mentioned. Of these, the only two effective are _artificial respiration and tracheotomy_ (or laryngotomy if preferred by the surgeon). Forcible artificial respiration by the Sylvester method, with the mouth gagged open and the tongue held forward by the tongue forceps, is frequently successful in getting over even a complete block, but the last resort of opening the air passage by the knife must not be delayed until too late. In deciding such a point, considerable judgment is of course called for. (2) NON-MECHANICAL.--Respiratory arrest.