=Cysts= are of frequent occurrence. They may be (1) of traumatic origin, containing a grumous material characteristic of the incompletely absorbed blood-clot; (2) of parasitic origin (e. g. echinococcus); (3) due to cystic degeneration of a sarcomatous, carcinomatous, or gummatous mass; or (4) simple arachnoid cysts (see p. 203). Many of these cysts are amenable to surgical treatment. =Carcinomata= are always secondary to cancer in other parts of the body--more especially carcinoma mammæ. They are usually multiple, and quite unsuited to surgical procedures. Any of these tumours may be complicated by the presence of internal hydrocephalus, this condition being dependent on the pressure exercised by the tumour on the veins of Galen, or on the interference with the normal transudation of fluid from one ventricle to another. =Symptomatology.= The symptoms resulting from tumour formation may be considered under two headings:-- 1. _General symptoms_, dependent on the general increase of intracranial pressure. 2. _Localizing symptoms_, dependent on local compression. Previous to discussing the symptomatology of brain tumours, it cannot be too forcibly urged that the surgeon is seldom justified in embarking on an extensive operation for tumour removal except after consultation with a neurologist. Ill-planned and ill-timed operations are usually disastrous in their results, and little creditable to cranio-cerebral surgery in general. On general grounds also, the symptomatology of brain tumours, as given below, must be accepted in the light in which it is offered, not representing the complete neurological aspect of the case, but affording an index to general diagnosis. For further information the reader is referred to more extensive works on brain tumours.[41] I. GENERAL PRESSURE SYMPTOMS Headache. Mental disturbances. Optic neuritis, &c. Vomiting. Alterations in pulse, respiration, and blood-pressure. Alterations in temperature. =Headache.= Headache is an almost constant symptom, and presumably dependent on general or local dural tension. It may be general or localized, intermittent or continuous, intense or comparatively mild in character. It is the more intense when the tumour develops in the confined space of the subtentorium, and when the tumour is of considerable size. In young subjects, before the skull is synostosed, some compensatory enlargement of the skull may postpone the development of headache, or diminish its intensity. The diagnostic value of a localized headache is rather problematical, but, when constantly referred to some particular region and when associated with definite tenderness on percussion, the localization of the headache assumes considerable importance in the regional determination of the tumour. Still, too much stress must not be placed on the site of the pain. A cerebellar tumour may give rise to frontal headache, and vice versa.