Through not a very short life, we have had ample opportunity of testing these principles by the bedside, and of endeavouring to connect some of them with the laws in obedience to which they occur; and we are free to declare our impression that when the book is studied with the requisite previous knowledge, and freedom from preconceived opinion; and when tested and carried out in _principle_, as distinguished from any adhesion to mere matters of _detail_; we think it infinitely more valuable than all other professional works whatever. In examining the truths it unfolds, or in our humble endeavours elsewhere at a more analytical or extended application of them, like Abernethy, we have rested our reasoning wholly on facts and observations which are acknowledged and indisputable. Whilst other views have only led to a practice in the highest degree empirical, or, what is worse, conjectural, those of Abernethy's lead often directly, but always _when duly studied_, to a practice at once clear, definite, and in the sense in which we shall qualify the word "positive,"—that is, one which gives us the power (when we really have the management of the case) of predicting the success or failure; which is at least a ripple indicative of a coming science. In order, however, to carry out this clearly, we shall at once add what we think necessary to the profession and the public on the subject. The _general relation_ of Abernethy's labours to a real and definite science will be better developed in our concluding Summary; when we may have an opportunity of stating what further appears to have been done, and what is yet required. It will have been perhaps already observed that Abernethy's views involve a few very simple propositions: first, that disturbance of a _part_ is competent to disturb the whole system; and conversely, that disturbance of the _whole system_ is competent to disturb any _part_. That the disturbance may _commence_ in the brain or nervous system, may then disturb the various organs, and that these may again by reflected action disturb the brain, and so reciprocally; and that in all these cases tranquillity of the digestive organs is of the very first consequence; not merely from its abstract importance, but from the influence it exerts on the state of the nervous system.