The cerebral anatomist, if destitute of any leading idea as to what he should be searching for, must be labouring under considerable disadvantage when he examines the intimate structure of the brain; and since the study of his choice must, from its peculiar intricacy, demand his best attention, he cannot be expected to be as profound in his pyschology as he is in his anatomy. “It is interesting to remark,” says Wagner, “that wherever an insight into the nature of the functions performed by an organ has been wanting, there has the structure also remained more or less obscure; we feel the want of everything like a guiding principle in the anatomical inquiry; of this truth we have satisfactory assurance in the cases of the thyroid, thymus, and supra-renal bodies and spleen.”* Then, as regards the pyschologist proper, if he devotes his days and nights to the analysis of the mind's conscious and expressed operations, it is not in human nature that he should be a professed and original anatomist as well. Indeed, division of labour is more necessary, perhaps, in this obscure field of research than in any other. Now, it is as a pyschologist who, in the interest of truth, has deemed it his duty to explain mental phenomena in such a way as to be in harmony with the ascertained structure of the brain, that the writer offers the following remarks, hoping that they may not be unserviceable to the cerebral anatomist.