After there is evidence of definite atrophic and degenerative disease in the brain, as indicated by great mental impairment and muscular paralysis, the mental and physical symptoms may be subject to great changes, without any apparent cause but vaso-motor disturbances, and alternating rapidly from extreme intellectual confusion and absence of mind to a clear, even if temporary, mental state. Less extreme changes in the condition of the mind are common. The mental symptoms, after the disease is pronounced, consist in an intensification of those already mentioned as characterizing the prodromal period—in an increase in the loss of power of control over all mental operations and in the loss of mental power, the two symptoms making progress side by side. In the form of the disease attended with maniacal excitement the prodromal period is usually shorter than in the others, but may last several years. After the prodromal period has passed the mental impairment increases, so that the judgment, memory, power of attention and expression grow progressively worse; and this impairment constitutes the only characteristic mental state universally present in all stages of general paralysis of the insane—namely, progressive dementia. The accidental symptoms may be those belonging to any type of insanity except logical systematized delusions. They very rarely simulate the states of mental defect and degeneration. If there are delusions of persecution, they are marked by a degree of confusion or incoherence not compatible with logical inference. The state of melancholia may change rapidly to mania, and the demented form may at an hour's notice become the excited. Where the symptoms of mental exaltation and depression alternate, resembling folie circulaire, the alternation is less regular than in alternating insanity properly speaking; hallucinations of sight and hearing and of all the special senses are quite common, although, as a rule, rather late symptoms, and then confused and often only partially intelligible. There are also all sorts of illusions and delusions.