The interest which attaches to the study of our bodily structure and powers is daily more widely felt, as the importance of the subject is more fully recognized, and especially as the relations which connect our bodily with our mental and moral life are better understood. Nor is this interest diminished by the difficulty with which its satisfaction is often attended. It is, indeed, stimulated rather than deadened by obstacles, and the desire to penetrate this mysterious world of material life, on which all that is best and highest in humanity rests as its foundation, is one that grows by disappointment. For the study of life is apt to end in a feeling of this kind. The multiplicity of the facts recorded by physiologists, the ingenuity of the experiments, the intricacy of the results—the astonishing amount of light, and the insuperable darkness—produce a mingled effect upon the mind. As observations multiply, doubts multiply with them. We are half disposed to ask whether we really know anything on the subject. Is there anything certain in physiology at all, besides what we can see?

If there is, it must be by virtue of some fixed and certain principles, which seem, indeed, to be sadly wanting in this department of science. We appear to be, in physiological inquiries, entirely at the mercy of our senses.