_Forgetfulness of certain Objects._--Of the effect of certain forms of disease, and also of age, in weakening the power of remembering names, I have already spoken. There are other effects, occasionally produced by disease upon this faculty of the mind, which are not so readily explained. In some cases, a certain class of objects, or the knowledge of certain persons, or of a particular language or some part of a language, as substantives, _e. g._, seems to be lost to the mind; in other cases, a certain portion of life is obliterated from the recollection. In cases of severe injury to the head, persons have forgotten some particular language; others have been unable to recall afterward the names of the most common objects, while the memory was at no loss for adjectives. A surgeon mentioned by Dr. Abercrombie, so far recovered from a fall as to give special directions respecting his own treatment, yet, for several days, lost all idea of having either a wife or children. The case of Mr. Tennent, who on recovering from apparent death, lost all knowledge of his past life, and was obliged to commence again the study of the alphabet, until after considerable time his knowledge suddenly returned to him, is too well known to require minute description. _Former Objects recalled._--In other instances, precisely the reverse occurs. Disease brings back to mind what has been long forgotten. Thus, persons in extreme sickness, or at the point of death, not unfrequently converse in languages which they have known only in youth. The case cited by Coleridge, and so frequently quoted, of the German servant girl, who in sickness was heard repeating passages of Greek, Latin, and Hebrew, which she had formerly heard her master repeat, as he walked in his study, but of whose meaning she had no idea, is in point in this connection. So also is the case of the Italian mentioned by Dr. Rush, who died in New York, and who, in the beginning of his sickness, spoke English, in the middle of it, French, but on the day of his death, nothing but Italian. A Lutheran clergyman of Philadelphia told Dr. Rush that it was not uncommon for the Germans and Swedes of his congregation, when near death, to speak and pray in their native languages, which some of them had probably not spoken for fifty years. These facts are sufficiently numerous to constitute a class by themselves; they seem to fall under some law of the physical system not yet clearly understood, and are, therefore, in the present state of our knowledge, incapable of explanation.