A bone-flap is framed suited to the occasion, and permitting adequate exposure of the dura. The question then arises as to whether the dura should be incised, the brain explored, and an attempt made at the removal of the tumour, or whether these procedures should be postponed till the patient shall have recovered from any shock attendant on the first stage. The two-stage operation--first advocated by Horsley--is insisted on by some surgeons. By others it is maintained that it is preferable to complete the operation at one sitting, mainly on the ground that two anæsthetics and two operations are more dangerous than one. As to which course should be adopted is entirely dependent on the general condition of the patient at the termination of the bone-flap formation. If his condition is quite satisfactory, if there has been but little hæmorrhage, and if the blood-pressure shows no tendency to drop, then it is perfectly justifiable to ‘carry on’, opening the dura mater and searching for the tumour. Still, as the shock entailed during the first stage may be considerable, as the surgeon cannot possibly foresee with certainty what lies beneath the dura mater, and as considerable time must elapse, and some hæmorrhage result during the further procedures required for the reflection of the dura mater and removal of the tumour, it follows that it is generally advisable to conduct the operation in two stages, the second operation being carried out some days later. Not less than five to seven days should elapse between stage one and stage two, the scalp-flap is then but lightly healed, whilst all blood-vessels should be sealed. The patient also will have entirely recovered from any shock attendant on the first stage. At the second stage, the dura may be more or less covered with a film of coagulated blood, meningeal arteries and the outline of venous sinuses being correspondingly obscured. Consequently, if the dural flap proposed for the second operation should include these structures, the meningeal vessels may be ligatured and the sinuses mapped out with guide-threads at the completion of the first stage. _Examination of the dura mater._ Considerable help may be obtained by examination of the dura mater, both with regard to the localization of the tumour and investigation as to its nature. Pulsation may be abolished or diminished, whilst the tenseness of the membrane is increased in direct proportion to the size and site of the tumour. The membrane also may be œdematous or adherent, anæmic in colour from pressure exercised by an underlying tumour, reddened from vascularization, grey-brown from the immediate presence of a malignant mass, plum-coloured from the adjacency of a subdural hæmorrhage, opaque from the presence of an arachnoid cyst. Some evidence as to the nature of the tumour may be obtained by palpation--fluctuation suggesting cyst formation, solidity pointing to more definite formation.