Many persons may labour under harmless delusions and still be fitted for their social duties; but should these illusions be such as to lead them to injure themselves or others in person or property, then the case is considered to require legal interference.
The approaches of insanity are variously characterised. Sometimes to all appearance, it comes on without warning, a sudden outbreak of violent mania being the first intimation of the disease; even in these cases, however, investigation will generally discover, that there has been some amount of preceding disorder, some sleeplessness, some unusual irritability, or mental excitement, perhaps concealed or controlled by the individual.
In other cases, the mental oddities, irritabilities or fluctuations of spirits have been evident, but too slight to excite apprehension. At the last, the acute attack may be induced by some severe or prolonged mental emotion, or by some physical depression.
The onset of the attack itself is frequently preceded by or accompanied with feverish symptoms, which particularly affect the head. In this case, the insanity is, probably at its first onset, accompanied with acute affection of the brain or its membranes, and partakes of the character of delirium properly so called.
Where the circumstances, such as hereditary predisposition or previous warning symptoms give rise to the suspicion of impending insanity, medical advise must at once be sought, preparatory to the one essential and merciful step — removal of the patient to an asylum. In the meanwhile, the most perfect quiet, both of body and mind, and the treatment recommended for delirium will be the most advisable mode of proceeding.
The malady may arise from a congenital deficiency of intellect, as in idiocy and imbecility, or in a perverted condition of the intellect expressed by certain delusions of the understanding; or the intellect may remain intact while the sentiments become depraved.
Taken from A Dictionary of Domestic Medicine and Surgery by Dr S Thomson MD LRCS, and Dr J C Steele MD, published in 1882 by Charles Griffin and Co of London