What are the ossence of niind and the essence of matter, and whether they are at bottom two things or one thiug, are beyoud asoertaimnent, and will probably eyer reniain ao. The nature of the union is a mystery, just aa the nature of the union between gravity and matter is a mystery ; in both cases we investígate only the law of the phenomena. As the problem is one of the connection between two systems of action, the first step towards its solution must be to resolve those two systems into their simplest elements. The structural elements of the nervous system are marvelously simple; they consist of microscopio cells and fibres, the former being seats or centers of force.and the latter being the ineans of transmitting it. Cells and fibres are the instrumenta of mental action, and, exactly as we rise in the scale of intelligence in aniniated creatures, there is an increase in the mass of the nervous centrs - that is a multiplication of the nerves and fibres which constitute theni. In man, the most intelligent of the animal series, the organ of intelligence is relatively very large, and attains tho higheBt degree of complexity. Prof. Bain representa the nervous elements of the human brain aa followa : " The thin cake of gray substanca surrounding the hemisphere of the brain, and extended into many doublings by the furrowed and oonvoluted struoture, is somewhat dinicult to uieasure. It has been estimated at upward of .500 squar inobes, or as uearly equal to a square surface of 18 inohes in the side. Ita thickness is variable, but on an average, it niay be stated at one-tenth of an inch. It is the largest accumulation of gray matter on the body. It ia made up of several layéis of gray aubatance (dividod by layéis of white substance. The gray substance is nearly compaot raass of corpuscles of variable size. The large caudate nerve cells are uiiugled with very small corpuscles less than the thousannth of an inch in diameter. Allowing for intervals, we may suppose that a linear row of 500 cells occupies an inch, thus giving 250,000 to the square inch for 300 inches. If one-half the thickness of the layer is made up of fibres, the corpuscles or cells, taken by themselves, would be a mass one-twentieth of an inch thick, say 16 cells in the depth. Multiplying these numbers together, we should reach a total of 1,200,000,000 cells, in the gray covering of the hemispheres. As every cell is united with at least two fibres, often many more, we may multiply this number by four for the nuniber of connecting fibres attached to the mass, which gives 4,800,000,000 fibres," Now in siyingsuch a wonderfulas organism this is the seat and embodiment of the miiid, we require to give distinctness to our conceptions, and are compelled to regard the connected cells and fibres as the simple instruments of simple mental processes as the whole fabric is the origin and measure of the whole mind. The corporal elements are cells and fibres - what are the physical elements in their lowest analysis? The oíd división of the mind iuto faculties - as reason, judgment, inemory and imagination- is insufficient, for these are far from being ultímate elementary processes, but are rather the most complex actions of the complex forces of the intelligence in different modes of exerciso. The latter psychology resolves all those so-calied faculties into a few constituents which form, if we may so speak, the contexture of the intellect. As Prof. Bain remarks : " We have no power of rnemory in radical aeparation from the power of reason or the power of imagination. The classification ís tainted with the fault called in logic 'cross división.' The real fundamental separation of the powerB of the intellect is into three f acts, called : 1. Discrimination, the sense, feeling, or consciousness of difference ; 2. Similarity, or the sense, feeling, or consciousness, of agreement ; and, 3. Retentiveness, or the power of memory or acquisition. These three functions, however niuch they are mingled in our mental operations, are yet totally distinct properties, and each the groundwork of a different superstructure. As an ultímate analysis of the mental powers, their number cannot be increased or dimished ; f ewer could or would not explain the facts, more are unnecessary. They are the intellect, the whole intellect, and nothing but the intellect."