INTRODUCTORY ESSAY. SOME ACCOUNT OF THE NERVES, AS A FOUNDATION FOR THE STUDY OF EXPRESSION. THE changes of the human countenance which accompany the exercise of the mind, afford at once the most familiar and the most interesting subject of study. But although we be continually and deeply conversant with those outward signs of emotion, we are scarcely conscious of the exertion, until by inquiry into their cause we try to recover our first impressions and to reason on them. How is it to be accounted for, that a subject more familiar to us than our mother tongue, and without which existence to most people would be indifferent and unprofitable, has not been brought into some relation with philosophy? In the author's opinion, it is to be attributed to a neglect of that close connexion which is established betwixt the operations of the mind and of the body, and to a very mistaken notion which has prevailed, that every thing interesting in anatomy has long since been discovered-that after the structure of animal bodies has been studied for so long a time, B and by a succession of so many eminent men, every thing must have been disclosed. Those who hold this opinion cannot be aware that every discovery in science opens a new field of inquiry, and that this is especially true of anatomy. No part of knowledge stands so much connected with the other departments, and is so universally dependent on discoveries in other sciences, as anatomy; if we understand by that term the knowledge of the functions as well as the structure of animal bodies. I have regretted the influence of this opinion on our students, because it takes from them that animation and pleasure which belong to their time of life, and their peculiar studies, which, if followed as they ought to be, afford an ever new hope and prospect of discovery. Nor ought the study of animal structure to be limited to that only which appears useful; but, on the contrary, extended in a liberal manner to all the ramifications which promise to improve our general knowledge. We never know to what useful conclusion the inquiry may lead, while it is sure to gratify us, to give rise to admiration, and a sort of involuntary praise. At one time I thought an apology was necessary for paying attention to expression, a subject of mere amusement, when I might have been more usefully employed; and now, if I shall have any reputation as a discoverer, I shall owe it principally to the views which this neglected subject has suggested to me. Here I first learned to look upon the fabric of the human body as a combination of parts which differed essentially from things of human invention that while the latter were pieces fitted and contrived to produce some ultimate effect, the former was cast with such perfection that each part performed many functions. I saw in the face so many different offices performed, that I began to inquire by what peculiarities of structure this was attained, and being led to examine other organs in the same manner, I laid the ground of my observations on the nervous system. A very remarkable error has been propagated, and as long as it continued there could be little known of the machinery of expression; nothing certainly, unless through our experience of the sympathies planted in our nature. These sympathies, when followed after the manner of philosophical inquiries, or pursued as matters of taste, led to nothing, or at most to some unsubstantial theory. However excellent the works may be which set forth these theories, however to be valued for the beauties of composition, for just sentiment and classical illustration, and all the graces of a cultivated understanding, they leave us as to knowledge where we were. The error to which I have alluded is a substantial one, being no less than a mistake as to the organs on which expression depends. There is a system of nerves extended over the frame called sympathetic, because they were universally believed to be the |