THE TONGUE.--For the Whitehead operation of removal of one half of the tongue, complete anæsthesia can be obtained by the infiltration method. A long needle is introduced at the tip of the tongue, and the injection carried in the middle line to a point behind the tumour. The mucous membrane of the floor of the mouth and the glosso-palatine fold are infiltrated, and a last injection made across the affected half of the tongue well behind the tumour. The tongue can be anæsthetised also by blocking the lingual nerve with a paraneural injection. The nerve lies under the mucous membrane of the mouth opposite the last molar tooth. If the tongue is drawn well over to the opposite side, the nerve can be felt and the injection made around it. The only drawback to this method is that it does not anæsthetise the posterior third, which is supplied by the glosso-pharyngeal nerve. OPERATIONS ON THE SKULL AND BRAIN can be readily performed by infiltration of the scalp. In the later stages of the recent war, a large proportion of operations on the skull and brain were performed under local anæsthesia. The brain itself is insensitive to touch and painful stimuli, and infiltration of the scalp is all that is necessary. A 1 per cent. solution of novocaine with adrenalin has been commonly employed, and is injected into the subaponeurotic space so as to surround the field of operation with a wall of anæsthetic solution--the method of Hackenbruch. The advantages are that hæmorrhage is reduced to a minimum, and the head can be conveniently and safely elevated and the intra-cranial tension thus reduced. Analgesia from the Application of Cocaine to the Eye or to a Mucous Surface. FOR OPERATIONS ON THE EYE.--Analgesia is obtained by the instillation of a few drops of a 4 per cent. solution into the conjunctival sac. This is repeated two or three times, and analgesia is obtained in five or ten minutes. It may be necessary to repeat the instillation during the course of the operation. FOR OPERATIONS ON THE NOSE, PHARYNX, OR LARYNX cocaine is commonly used. A 5 or 10 per cent. solution is employed and is merely painted on the surface. Care must be taken that such strong solutions are not swallowed. CHAPTER XXI. SPINAL ANÆSTHESIA.