572 THE POPULAR SCIENCE MONTHLY. 



tional activity is modified by structural changes. There is not a new 

 line of thought instituted, leading in opposite directions to the normal 

 thought, but a misdh-ection of the ordinary mental processes. There 

 is, however, a certain amount of illusion which, when pronounced, or 

 when the effect upon the brain-cells is such as to cause an evolution 

 of distinctly-erroneous thought, or actual hallucinations, indicates 

 that the frontier of sanity is crossed. 



Such considerations will enable us to observe and to comprehend 

 that initiatory stage of mental impairment which precedes obvious 

 and well-marked dotage. The earlier stages, the lighter shades of 

 mental failure, of waning brain-power, are distinct enough to the 

 trained eye, long before those more obvious changes are reached 

 which are recognized by the untrained observer. Such mental changes 

 are commonly found in those undergoing degenerative physical 

 changes, not only in the very aged, but in those passing into prema- 

 ture decay ; in fact, mental impairment and decay are but the evi- 

 dences or outcomes of the implications of brain-tissue in the general 

 degeneration. We are, of course, most familiar with such changes in 

 the very old, in whom we regard them as almost normal. The mental 

 grasp is imperfect and illusive ; petulance and caprice are the charac- 

 teristics, especially of those in whom the intellect was never very 

 strong. Their intellectual vision is deceptive and untrustworthy. A 

 dim consciousness of some such change obtains in the mind, and makes 

 them deeply suspicious and extremely susceptible, and ready to take 

 offense at the slightest indication by others of a knowledge of their 

 growing incapacity. Nor can we feel surprised at this sensitive 

 suspiciousness. Mental decay cannot be a pleasant matter for those 

 undergoing it, and no wonder they are excessively jealous of any alter- 

 ation of manner or attitude. 



A similar condition of enfeeblement, combined with excessive 

 jealousy and deep-rooted suspicion, is furnished by those who have 

 anticipated the normal time of senile decay by habits of drunkenness. 

 The man who is beginning to yield under persistent alcoholization, 

 and who feels that his powers are giving way, is generally suspicious 

 and jealous, if not actually malicious. The intellect undergoing pre- 

 mature degeneracy is more readily and easily provoked than is that 

 of a person entering normal dotage ; while there is often coexistent a 

 certain amount of spasmodic vigor of temporary active irritability. 

 Such persons are simply dangerous to those dependent upon them, and 

 not to be trusted their mischievousness being only restrained by 

 their incapacity to execute or put in force their malicious designs. 



There are two other mental attitudes which are not directly asso- 

 ciated with bodily disease, but which exercise so distinct an influence 

 over physical conditions, especially in sickness, that they may not im- 

 properly be considered here, though not quite falling within the scope 

 of this paper. One is that condition of mental impairment in which 



