Fig. 4 shows a suitable apparatus. The needles are thrust into the loose areolar tissue under the breast, one on each side, and a pint or more of fluid is _slowly_ run in from the reservoir. CHAPTER III. ASPHYXIA OR ANOXÆMIA. Some degree of asphyxia is a common complication of inhalational anæsthesia: indeed some small degree of it is almost unavoidable. It is hardly too much to say that the difference between a good and a bad anæsthetist is that the one recognises and deals with asphyxia in its early stages, while the other allows it to assume serious proportions before he becomes aware of its existence. The man who only realises that asphyxia is present when the patient is deeply cyanosed and has ceased to be able to draw any air at all into his chest may know much of the physiology of anæsthetic drugs, and be well up in complicated anæsthetic apparatus, but knows nothing of the proper practice of anæsthesia. Asphyxia arises during anæsthesia from several causes. In the first place, the drug which the patient is inhaling and absorbing into the blood, turns out from his red corpuscles a corresponding quantity of oxygen. While this is only seen in its extreme form in the case of nitrous oxide gas, it is a factor acting even in the case of other anæsthetics. Secondly, during deep anæsthesia, the respiratory centre may be somewhat depressed, and the force and frequency of the respiratory act diminished. Thirdly, the respiratory passages may be partially or wholly occluded from _mechanical_ causes. This is far the most important type of asphyxia, being the most common, the most fatal, and the most easily prevented. Common Causes of Mechanical Asphyxia. (1) CLENCHING OF THE JAWS arises not uncommonly during anæsthesia, being specially frequent towards the end of the induction period. Since a very large proportion of individuals have nasal passages insufficient in bore to carry the full volume of respired air, respiration must be obstructed if the jaws are clenched. (2) FALLING BACK OF THE LOWER JAW AND BASE OF THE TONGUE OVER THE EPIGLOTTIS.--This is always liable to happen after the muscles are deeply relaxed. (3) MUCOUS OR BLOOD OR A FOREIGN BODY IS DRAWN BY INSPIRATION INTO THE AIR PASSAGES.--Changes of position of the head may release mucous which has been gathering in some parts of the mouth or pharynx. For instance, if the head has been lying on the side for some time, a pool of mucous or saliva commonly gathers in the most dependent cheek, and unless this is mopped out before the head is brought into the mesial position, this pool will be suddenly tipped backwards, and very probably drawn into the larynx. Again, in operations upon the nasal or oral cavities, blood is always liable to be inspired, and not a few teeth have found their way into the air passages in the practices of dental surgeons who do not take precautions against this accident.