The general details of the operation as enumerated above may require amendment as our knowledge increases. Sufficient has been said, however, to point out the various methods of approach and the advantages claimed for the nasal route. =Results of operation on brain tumours.= Statistics are always fallacious, and this is especially the case with regard to operations on tumours of the brain. Few surgeons have operated on a sufficient number of cases to compile satisfactory statistical tables. These tables are generally made up from the combined experience of many operators, all using their own methods. The following, however, will serve to give an approximate idea as to mortality, &c. _Mortality._ From earlier records the immediate mortality was estimated at 30-40 per cent. Duret, however, records 400 cases with a mortality of 19·5 per cent., 58 cases dying from shock, 10 from hyperpyrexia, and 10 from hæmorrhage. In my own practice, the mortality may be estimated at a much lower figure. Perhaps I may be too conservative, but I hold the view that, unless the tumour is readily exposed and equally readily removable, it is inadvisable to carry out further measures for its eradication. Moreover, the general technique of brain surgery has advanced with rapid strides, and the question of early and accurate localization has received equal attention. The mortality has diminished proportionately, and may be estimated at less than 20 per cent. So much depends on the surgeon and on the nature of the tumour, its position and localization, that it is impossible to make any absolute statement as to the risk to life attendant on operation. If all tumours were fibromata, cortically situated, and accurately diagnosed, the operation, in the hands of a skilled neurological surgeon, should present but a very low mortality. So long, however, as surgeons will persist in burrowing into the brain substance for a supposed subcortical tumour, so long will the mortality remain high. The great secret in operating on a brain tumour lies in knowing when to terminate the attempt at removal of the tumour and when to rest content with a pure ‘decompression’. It is obvious, therefore, that cortical tumours--more especially such as give rise to early localizing symptoms, e.g. Rolandic tumours--offer a better prognosis than when the surgeon has to deal with subcortical, central, and basal tumour formation. _The mortality according to the region affected._ The following table, from a series collected by Knapp, supplies valuable information as to the regional mortality. Frontal tumours 32 cases Mortality, 25 per cent. Central „ 231 „ „ 23 „ Parietal „ 29 „ „ 41 „ Temporal „ 17 „ „ 29 „ Occipital „ 10 „ „ 20 „ Cerebellar „ 54 „ „ 45 „