If a man is habitually subject to many and various hallucinations, and his sane judgment esteems them to be such, they are undoubtedly unusual phenomena, but they do not in any way injure the rational exercise of the mind.  It is only when he believes the images to be real that the abnormal state begins, termed delirium if it is of short duration, and madness if it is permanent.  We must examine hallucination under these new conditions.

In the delirium of fever, or in various forms of disease, the cerebral excitement is so great that not only the deliberate exercise of reason, but the power of estimating external objects is lost, and the organs of the senses are so completely altered, that the perceptions themselves are exaggerated and confused.  In this state hallucination reaches its highest point, and the patient sees, hears, and feels, directly or indirectly, strange and terrible things:  wild beasts, enemies of all kind, torments; or again, pleasing and agreeable images.  Independently of the alteration in various sensations produced by the morbid alteration of the special organs which induce them, the real cause of this phenomenon consists in the objection of mental sensations and images.  Such an objection of images or sensations, considered in the act which transforms them into a reality, depends on the same cause as all other acts of perception; there is always an entification of the phenomenon, which in this case is a vivid internal image, appearing to be external and real.

The entification of images is still more direct and powerful because in this morbid crisis the necessary corrections made by reason cannot take place, since the sick man is for the time deprived of it, and he is in fact a dreamer, whose condition is intensified by abnormal excitement.  Entification is now displayed in its nude and native state, and serves to explain the constant mental process, and the true nature of the representations of the intellect.  The transition is easy from delirium to madness, for although an insane person is not always delirious, but sometimes calm and composed, yet there is a fundamental resemblance to delirium in the change in his states of consciousness and its relative organs, which imply a constant hallucination.  The most famous and acute physicians of the insane estimate that eighty out of a hundred insane persons are subject to hallucinations.  The morbid condition which generates them is also produced by debility, by anaemia, and the senile decay of the cerebral organs, since they occur in dementia, idiocy, and old age, and the physiological and mental causes are the same; the power of fixing the attention and governing the thoughts is diminished, owing to the weakening of the vivid consciousness of the external world, produced by a torpidity of the afferent organs.  In these cases the recollections which are not altogether lost sometimes reappear as hallucinations.  The hallucinations of madness, in its various forms of dementia, idiocy,