Too frequently the condition has never been suspected, and a fatality occurs from sudden syncope, usually during the induction period, but occasionally during the progress of the operation. It would, however, be fallacious to suppose that an anæsthetic is necessarily fatal even to an undoubted case. If the drug (preferably ether) be given with great care, and the operation done carefully at a level of anæsthesia neither too light nor too deep, there is every reason to believe that the danger can be, and often is, successfully averted. At the same time, it must be understood that in a known case, operation should always be avoided or deferred if possible. CHAPTER XVII. THE SEQUELÆ OF ANÆSTHESIA. Respiratory System. After operations performed under any form of anæsthesia, even spinal, there is always a possibility of pneumonia or bronchitis. The anæsthetic itself is not always to blame. The patient has suffered trauma and is confined to bed, and may develop a hypostatic pneumonia just as a person who has suffered from a fractured thigh so commonly does, even though he has had no anæsthetic at all. It is probable that organisms, capable under certain circumstances of causing inflammatory disease of the respiratory tract, are present in a large proportion of apparently healthy people. Pneumococci and streptococci of varying strains may be grown from nasal or pharyngeal secretions of patients who suffer from catarrh of these regions, and may reappear upon slight provocation even when prolonged treatment had apparently banished them permanently. All that is required to start an acute infection of lungs or bronchi, is some factor that depresses vitality and lowers body resistance to the organism. And if in addition use has been made of an inhalational anæsthetic such as ether, which may cause an immediate and fairly acute congestion of the respiratory mucous membranes, it is not to be wondered at that serious sequelæ follow in a certain proportion of cases. Laboratory results go to show that ether lowers the opsonic index of the blood to pneumococci and streptococci, but without placing undue emphasis upon a mere isolated phenomenon such as that, it is plain that the whole conditions of the patient after operation are favourable to the occurrence of pneumonia or bronchitis, and that of all anæsthetics ether is the most likely to be the determining factor.