A careful study of cerebral physiology leads us deeper into the mysteries of the human constitution, and to the philosophical contemplation of the relations of mind and body. Self-culture implies not only a knowledge of the powers of the mind, but also how to direct and use them for its own improvement, and he who has the key to self-knowledge, can unlock the mysteries of human nature and be eminently serviceable to the worlds For centuries the mind has been spreading out its treasury of revelations, to be turned to practical account, in ascertaining the constitution, and determining better methods of treating disease. Since comparative anatomists and physiologists have revealed the structure of animals and the functions of their organs, from the lowest protozoan to the highest vertebrate, the physician may avail himself of this knowledge, and thus gain a deeper insight into the structure and physiology of man. An intimate acquaintance with the physical, is a necessary preparation for the study of the psychical life, for it leads to the understanding of their mutual relations and reactions, both in health and disease. Consciousness, or the knowledge of sensations and mental operations, has been variously defined. It is employed as a collective term to express all the psychical states, and is the power by which the soul knows its own existence. It is the immediate knowledge of any object whatever, and seems to comprise, in its broadest signification, both matter and mind, for all objects are inseparable from the cognizance of them. Hence, the significance of the terms, subjective-consciousness and objective-consciousness. People are better satisfied with their knowledge of matter than with their conceptions of the nature of mind. THE NATURE OF MIND. Since this subject is being discussed by our most distinguished scientists, we will conclude this chapter with an extract from a lecture delivered by Prof. Burt G. Wilder, at the American Institute: