The leading topics under which these famous lectures are comprised are: Nutrition, Hypertrophy, Atrophy, Repair, Inflammation, Mortification, Specific Diseases, and Tumours. The concluding passage of the second lecture, on “The Conditions Necessary to Healthy Nutrition,” is a fine exposition of a view of the relation between the mind and a changing brain. “In all these things, as in the phenomena of symmetrical disease, we have proofs of the surpassing precision of the formative process, a precision so exact that, as we may say, a mark once made upon a particle of blood or tissue is not for years effaced from its successors. And this seems to be a truth of widest application; and I can hardly doubt that herein is the solution of what has been made a hindrance to the reception of the whole truth concerning the connection of an immaterial mind with the brain. When the brain is said to be essential, as the organ or instrument of the mind in its relations with the external world, not only to the perception of sensations, but to the subsequent intellectual acts, and especially to the memory, of things which have been the objects of sense—it is asked, how can the brain be the organ of memory when you suppose its substance to be ever changing? or how is it that your assumed nutritive change of all the particles of the brain is not as destructive of all memory and knowledge of sensuous things as the sudden destruction by some great injury is? The answer is—because of the exactness of assimilation accomplished in the formative process; the effect once produced by an impression upon the brain, whether in perception or in intellectual act, is fixed and there retained; because the part, be it what it may, which has been thereby changed, is exactly represented in the part which, in the course of nutrition, succeeds to it. Thus, in the recollection of sensuous things, the mind refers to a brain in which are retained the effects, or rather the likenesses of changes that past impressions and intellectual acts had made. As, in some way passing far our knowledge, the mind perceived and took cognisance of the change made by the first impression of an object, acting through the sense organs on the brain; so afterwards, it perceives and recognises the likeness of that change in the parts inserted in the process of nutrition. “Yet here also the tendency to revert to the former condition, or to change with advancing years, may interfere. The impress may be gradually lost or superseded, and the mind, in its own immortal nature unchanged, and immutable by anything of earth, no longer finds in the brain the traces of the past.”