Mild glottic spasm may supervene on the passage of the catheter but this rapidly passes off. At first the degree of concentration of the vapour should be low or irritation will result, evidenced by spasm and coughing. The strength of the vapour is gradually increased until the necessary concentration is attained. The pressure should vary according to the requirements of the case and should range between 10 mm. to 25 mm. Hg. The safety valve must be set so as to make any pressure above this impossible. In the majority of cases the course of anæsthesia is smooth and uneventful; the colour remains a rosy pink, the pulse is good, and the respirations quiet and regular. It is undesirable that the respiratory movements should be abolished altogether; their presence indicates that neither the central nor the peripheral respiratory mechanism is being overdosed with ether. Theoretically, the constant plus-pressure in the lungs might be thought to interfere with the circulation in the large veins, and in the pulmonary vessels themselves. It is therefore well to reduce the pressure in the catheter to zero every minute by opening the tap provided for the purpose for a second or two. At the conclusion of the operation, before withdrawing the catheter it is well to flush out the lungs with air so as to remove any ether vapour that is present. In a certain number of cases, notably in big alcoholic subjects, difficulty may be experienced in securing a sufficiently deep anæsthesia with good relaxation. It is seldom, however, that patience and the careful introduction of a stronger vapour will not suffice to overcome this. In alcoholic subjects, as previously suggested, preliminary medication with scopolamine and morphia will help. It really becomes a question, if one may put it so, of coaxing the unconscious patient to tolerate an ether vapour of adequate strength. Advantages and Special Indications. The general opinion of anæsthetists appears strongly to favour the view that the absence of strain and the perfect æration in intratracheal ether insufflation tend to lessen the shock of operation. The post-operative history of patients also suggests that there is a lessened liability to pulmonary complications as compared with cases in which ether has been administered by other methods. Dr Elsberg[8] of New York in this connection writes: “The absence of any pulmonary complications has led us to use this method of anæsthesia in all patients in whom pulmonary complications were to be feared after an anæsthesia or operation. Thus on all asthmatics, in patients with chronic bronchitis and emphysema, in patients who require gastric resection and the like, we no longer, during two years, have seen the much dreaded post-operative pneumonia wherever intratracheal anæsthesia was used.”