This paper deals with some of the anatomic and physiologic peculiarities which govern the operative treatment of certain lesions of the contents of the anterior cranial fossae, and includes a description of a method of exposing the latter. It is not intended to be in itself a complete survey of the field; many practical points have been recorded by other surgeons, and reference will be made to these in the appropriate places. Details concerning the various types of lesions are best assembled in papers which are confined to a particular type; because many such studies are now available, it may be not unprofitable to revert now and then to a regional outlook, by attempting to combine in broad outline an account of the surgical difficulties which are the sum, or perhaps even the product, of lesion and site. Although much of what follows may be already familiar to individual surgeons,