‘I should anticipate from cortical irritation bilateral pupillary dilatation, perhaps more marked on the opposite side: from pressure the opposite effects, so far as mere cortical paralysis goes, but this would be more liable to be vitiated by vascular changes--the complex condition seen in coma. It is very difficult to elicit pupillary constriction by cortical stimuli--very easy to elicit dilatation, but always bilateral though often more marked on the opposite side.’ In cases examined by me the following conditions were found:-- Pupils equal 46 per cent. of cases Pupils constricted on the affected side 36 per cent. of cases Pupils dilated on the affected side 18 per cent. of cases From my experience, therefore, and from that of the authorities quoted above, it would appear that alterations in the size of the pupil are of very doubtful significance in the diagnosis of middle meningeal hæmorrhage, and that the ‘Hutchinson pupil’ is but rarely observed. The results obtained by ophthalmoscopic examination are of much greater value. Such investigations should be carried out as a routine procedure. In the earlier stages of the hæmorrhage some œdema of the disk, together with dilatation of retinal veins and diminution in the calibre of the arteries, will be observed on the affected side. This affords a most valuable aid in the differential diagnosis as to the side on which the hæmorrhage is situated--not always such a simple matter as appears at first sight. =Treatment.= Operation is indicated in all cases of middle meningeal hæmorrhage if the condition of the patient be compatible with such treatment. The earlier the operation is carried out the better. =Operation.= _For Hæmorrhage from the anterior branch._ After the usual preparatory treatment, the ‘site of election’ for trephining is marked out on the scalp by taking a point which lies 2 inches posterior to the external angular frontal process, and the same distance above the zygoma. A bradawl may be introduced so as to indent the external table of the skull, thus aiding the subsequent accurate application of the trephine. [Illustration: FIG. 52A. EXPOSURE OF THE BRANCHES OF THE MIDDLE MENINGEAL ARTERY. _First stage._ Suitable scalp-flaps have been turned down, and the skull has been trephined over the ‘sites of election’ for exposure of both anterior and posterior branches.] [Illustration: FIG. 52B. EXPOSURE OF THE BRANCHES OF THE MIDDLE MENINGEAL ARTERY. _Second stage._ The trephine-holes have been enlarged with the craniectomy forceps in the required directions.] The incision commences immediately posterior to the external angular frontal process, curves upwards and backwards along the temporal crest, and terminates in front of the tragus of the ear. The flap, comprising skin, temporal fascia and muscle, and pericranium, is turned to its zygomatic base and all bleeding-points secured.