In deciding whether or not to use in a given case the BNA term many difficult cases arose. Will the common English name _innominate_ bone (os innominatum) be replaced by the BNA term _os coxæ_ or _coxal bone_? We have held this to be highly improbable, and have therefore used the term _innominate bone_, merely citing _os coxæ_ (BNA) as a synonym. In the same way we have used _centrum_ as a designation of a part of a vertebra, in place of _corpus_ (BNA); _premaxillary_ bone or _premaxilla_ in place of _os incisivum_ (BNA); _malar_ bone in place of _os zygomaticum_ (BNA); _trapezoid_ as a name of one of the bones of the carpus, in place of _os multangulum minus_ (BNA), etc. In other cases where it has seemed probable that the BNA term would come into common use, though now unfamiliar, this and the more common English expression are both used or used alternatively; such has been the case, for example, with the Gasserian ganglion or semilunar ganglion (BNA). In naming the cerebral sulci and gyri the system in use for man is not well fitted for bringing out the plan of those in the brain of the cat, so that it was necessary to reject the BNA names for these structures. As to the use of the Latin terms and their equivalents in English form, we have made a practice of employing in the text sometimes one, sometimes the other; this has the advantage of giving variety, and of impressing the interchangeability of the Latin and English forms on the mind of the student. Where a given structure is called by two equally well-known names, we have used both, holding that the student should become familiar with each and recognize their identity of meaning. In general we have maintained the principle that the primary purpose of such a work as the present is not to illustrate or defend any particular system of nomenclature, but to aid in obtaining a knowledge of the structures themselves. With this end in view, we have used such terms as would in our judgment best subserve this purpose, making the BNA system, as the one most likely to prevail, our basis. In applying the system we have had to keep in mind a number of sometimes conflicting principles. In some cases the judgment of other anatomists will doubtless differ from our own; but this we feel to be inevitable. The matter of an absolutely uniform nomenclature is not ripe for settlement at the present time.