There will no doubt be a difficulty in the investigation of a science which is in itself so complicated, and which has hitherto been so little understood; but this is only an additional reason why it should be begun in a proper manner, and pursued with energy. The mode of procedure is the chief object of difficulty; but the experience and success of investigators in the other sciences, will be of great advantage in directing us in this. In the sciences of anatomy and physiology, for example, the investigations of the philosopher are designed to direct the several operations of the physician, the surgeon, and the dentist; in the same way as the investigations of the Educationist are intended to direct the operations of the Teacher. Now the mode of procedure in those sciences for such purposes is well known, and forms an excellent example for us in the present case. The duty of the anatomist, or physiologist, is simply to examine the operations of Nature in the animal economy, and the plans which she adopts for accomplishing her objects during health, and for throwing off impediments during disease. In conducting his investigations, the enquirer begins by taking a general view of the whole subject, and then separating and defining its leading parts. Pulsation, respiration, digestion, and the various secretions and excretions of the body, are defined, and their general connection with each other correctly ascertained. These form his starting points; and then, taking each in its turn, he sets himself to discover the principles, or laws, which regulate its working in a healthy state;--what it is that promotes the circulation or stagnation of the blood, the bracing or relaxing of the nerves, the several processes in digestion, and the various functions of the skin and viscera. These are all first ascertained by observation and experience, and then, if necessary, established by experiment.