is merely a legal term to designate those individuals whose actions are opposed to the social state and who are not responsible for them.  In insanity there is falsity in impressions, in conceptions, in judgment, a defective power of will and an uncontrollable violence of emotion.  The individual is prevented from thinking the thoughts or feeling the feelings and doing the duties of the social body in the community in which he lives.  The insane are out of harmony with their social environment, but not necessarily in opposition to it.

There is no very sharp line between insanity and criminality.  The criminal is in direct antagonism to the laws of social life.  An insane person may cause the same injury to society as a criminal, but his actions are not voluntary, whereas the criminal is one who can control his actions, but does not.  Mentally degenerated persons, however, can be both insane and criminal.  Whatever the state of society, this reprobates the actions of one opposed to it; in a society in which it were usual to appropriate the possessions of others or to devour unpleasant or useless relatives, virtue and lack of appetite would be reprobated as unsocial.

The symptoms of insanity or the manner in which the defective action of the brain expresses itself and the various underlying pathological changes vary, and by combining these it has been possible to subdivide insanity into a number of distinct forms.  There are both intrinsic and extrinsic causes of insanity.  The intrinsic are the structural differences in the brain as compared with the normal or usual, whether these are due to imperfection in development or to defective heredity or to the injury of disease; the extrinsic causes are those which come from without and bring the intrinsic into activity.  Syphilis is a frequent cause of insanity, and probably the only cause of the condition known as general paralysis of the insane, acting by means of the injury which it produces in the cortex of the brain.  The abuse of alcohol is another fertile cause, but the changes produced in this are not so obvious as in the case of syphilis.  Tumors of the brain are not infrequently a cause, and the same is true of infections, even those not located in the brain.  How susceptible the brain is to the effects of the toxines of the infectious diseases is shown in the frequency of delirium in these diseases.  There is an interesting relation between this and alcoholism.  Alcohol abuse may produce injury, but not sufficient to manifest itself under ordinary conditions; when, however, the action of toxic substance is superadded to the effect of the alcohol the delirium of fever is more marked.