Too long have we reversed the natural order of things, and commenced the study of medicine where we ought rather to have left it off. Too long have we striven, by studying pathology ere we were sufficiently acquainted with physiology, to place the pyramid on its apex instead of on its base; and thus it is we remained so long ignorant of the fundamental doctrine, that the same laws which regulate health, regulate disease. Nature does nothing on a small scale, and the more we study her the more we admire the uniformity, and extensive applicability of her laws. If we pry into the ultimate structure of our bones, we find they receive their nutriment by a system of irrigation, carried on through lakes, and rivers (lacunæ, and canaliculi); and if we examine the periosteum surrounding them, the ligaments attaching them, or the muscles covering them, we still find, that, notwithstanding the diversity in structure, and use, the one system of irrigation pervades them all. We may even go a step further, and say that the same law which governs the animal governs also the vegetable kingdom. Indeed, the further science advances, the more apparent does it become, that not only the animal, and vegetable, but even the organic, and inorganic, form but one world, regulated by the same laws. A knowledge of organization, important though it be, is yet less indispensable to the physician than a knowledge of healthy function, for it is the latter which elucidates the dark problems of life, it is the latter which proves the golden key to the comprehension of disease. Although not even the most ardent admirers of medicine can say, that it as yet merits the name of an exact science, this ought neither to destroy our hopes nor trammel our labours. With the stethescope, microscope, and other physical means of diagnosis a new era dawned upon our art; and now the members of the new school which is rising up, and carrying chemistry into the domains of medicine, are the pioneers of the revolution which is soon to follow. If we look back to what the exact sciences of to-day were in former times, we shall find they were much less perfect then, than medicine is now. Astronomy and chemistry were but astrology and alchemy. If, then, we draw a picture of the future from the progress of the past, we need have no hesitation in saying that chemistry rightly applied, and physiology justly interpreted will, ere many generations pass away, reveal the deepest secrets of diseased action, and although unable to banish death, will yet enable the practitioner to follow with unerring certainty the various morbid changes occurring in the frame. 77, HARLEY STREET, CAVENDISH SQUARE, _March, 1863_. CONTENTS. PAGE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 1