(4) SPASM OF THE ADDUCTORS OF THE VOCAL CORDS is one of the most common and most baffling incidents in anæsthesia. It announces its presence by the commencement of _laryngeal stridor_, a high-pitched crowing noise, which is as annoying for the surgeon and anæsthetist to hear as it is detrimental to the progress of a smooth anæsthesia. Inspired mucous or blood almost invariably sets it up, and the two conditions of fluid in the larynx and narrowing of the glottis from approximation of the cords, add their effects together, with resulting obstruction of a high degree. Laryngeal stridor, however, frequently occurs even when no fluid has been inspirated. It may be set up as a reflex from the area of operation. Dilatation of the sphincter ani, and removal of the prepuce in circumcision, are two common examples of this. It is also undoubtedly sometimes caused by giving too strong a vapour during the latter part of the induction stage. Stridor unfortunately sometimes occurs from no obvious cause at all, or to speak more correctly, from causes which are at present not known to us. It is the author’s belief that one of these causes may prove to be _morphia_ given as a preliminary to inhalational anæsthesia. In his experience, stridor has been more frequent with morphia than without, particularly if chloroform be the anæsthetic chosen. Beyond that he cannot at present go. (5) PRESSURE UPON THE AIR PASSAGES OF NEOPLASTIC OR INFLAMMATORY SWELLINGS IN THE NECK.--In such cases any obstruction which may exist before induction will probably become intensified during the process, and a complete arrest of respiration is not uncommon. Large goîtres are the most common type of neoplasm to give trouble, and all acute inflammatory conditions in the neck which extend towards the trachea are notorious for their tendency to give cause for anxiety during anæsthesia. The Physiology of Asphyxia. An animal, subjected to asphyxia, either mechanically or otherwise, shows the following signs:-- (_a_) _Increase of the force and frequency of the respiratory movements of chest and abdomen._ Even though there be a complete mechanical obstruction, increased efforts to breathe will still be made for some moments, although air no longer passes in and out of the chest. (_b_) There is a considerable rise of blood pressure owing to a high degree of vaso-construction. (_c_) The pupils dilate. (_d_) Generalised convulsions. (_e_) The animal succumbs finally from cardiac failure. No heart muscle can continue to function properly if supplied by the coronary arteries with venous blood. Moreover, the heart pump has to act against the greatly increased peripheral resistance induced by vaso-constriction. It must therefore be a matter of time only when the strongest and healthiest heart will cease to contract under the abnormal conditions of asphyxia.