DEMENTIA. In Medical Jurispru dence. That form of insanity which is characterized by mental weakness and de crepitude, and by total inability to reason correctly or incorrectly.
The mind dwells only in the past, and the thoughts succeed one another without any obvious bond of association. Delusions, if they exist, are transitory, and leave no permanent impression ; and for every thing recent the memory ie exceedingly weak. In mania, the action of the mind is marked by force, hurry, end intensity; in dementia, by slowness and weakness. It is mostly the sequel of mania, of which, in fact, it is the natural termina tion. Occasionally it occurs in an acute form in young subjects; and here only it is curable. In old men, in whom it often occurs, it is called senile de mentia, and it indicates the breaking down of the mental powers in advance of the bodily decay. It is this form of dementia only which gives rise to litigation; for in the others the incompetency is too patent to admit of question. It cannot be de scribed by any positive characters, because it dif fers in the different stages of its progress, varying from simple lapse of memory to complete inability 'to recognize persons or things. And it must be borne in mind that often the mental infirmity is not so serious ns might be supposed at first sight. Many an old man who seems to be scarcely con scious of what is passing around him, sod is guilty of frequent breaches of decorum, needs only to have his attention aroused to a matter in which he is deeply interested, to show no lack of vigor or acute ness. In other words, the mind may be damaged superficially( to use a figure), while it may be sound at the core. And therefore it is that one may be quite oblivious of names and dates, while compre hending perfectly well his relations to others and the interests in which he was concerned. It fol lows that the impressions made upon casual or ig norant observers in regard to the mental condition are of far less value than those made upon persons who have been well acqnainted with his habits and have had occasion to test the vigor of his faculties.
The wills of old men are often contested on the ground of senile dementia, and the conflicting tes timony of observers, the proofs of foreign influ ence, and the indications of mental capacity all combine to render it no easy task to arrive at a satisfactory conclusion. The only general rule of much practical value is that oompetency must be always measured, not by any fancied standard of intellect, hut solely by the requirements of the act in question. A small and familiar matter would require less mental power than one complicated in its details and somewhat new to the perience. Less capacity would be to dis tribute an estate between a wife and child than between a multitude of relatives with unequal claims upon his bounty. Such is the principle; and the ends of justice cannot be better served than by its correot and faithful application. Of course, there will always be more or less difficulty ; but generally, by discarding all legal and metaphy sical subleties and following the leading of can, mon sense, it will be satisfactorily surmounted.
The legal principles by which the courts are gov erned are not essentially .different whether the mental incapacity proceed from dementia or mania. If the will coincides with the previously expressed wishes of the testator, if it recognizes the elnima of those who stood in near relation to him, if it shows no indications of undue influence,—if, in short, it is a rational act rationally done,—it will be established, and very properly so, though there may have been considerable impairment of mind. 2 Phill. Ecel. 449; 3 Wash. C. C. 580; 4 id. 262.
See INSANITY.