As Erbes states it "the effect the scheme of cranial muscles have had and still have upon the conformation of the skull, and, consequently, had in determining the location of those areas and in giving brain and mind a character approximately identical from end to end of the scale of living things possessing the cerebro-spinal nervous system. In so far as the neural matter is dependent upon the cranial muscles--aside from the sensory stimuli--so far, likewise are the psychic manifestations, through tongue or limb, modified by variations in those muscles that, after their creative task is done, assume a vasomotor control over their respective areas." The same writer also says: "The cerebral mass owes its location and subsequent expansion, moreover, in a measure that mind owes its character, primarily to the action of the muscles attached to and lying upon its peripheral covering, the skull; these same muscles thereafter, through exercising a cerebral vasomotor control, act in the nature of keys for calling the evolved dependent brain areas into play, singly and en masse." Others have held that the development of certain areas of the surface of the skull is due to peculiar neural or nervous, activities having their seat in certain parts of the brain adjacent to their appropriate area of the skull, but these theories fail to explain the nature of the relation between the mind, brain and the "nerve centres" aforesaid. These several authorities, and others, however, agree upon the fact that certain areas of the brain are associated in some way with certain mental states; and that these brain areas register their relative activity upon the areas of the skull adjacent thereto; and that the _activity_ and _power_ of each brain area, or faculty, is denoted by the _size_ of the associated skull-area. Thus, the outward facts claimed by phrenology are admitted, while their theories of cause are disputed. In this book we shall rest content with these "outward facts" of phrenology, and shall not concern ourselves with the various theories which seek to explain them, preferring to leave that task for others. In considering the subject of the Outer Form associated with the Inner State of Human Nature, we shall merely claim that _mental states manifest in outer form in the shape and size of the head; and that certain areas of the skull are thus associated with certain mental states, the size and shape of the former denoting the degree of activity of the latter_.