"The number of prisoners who are mentally defective is the subject of the very widest difference of opinion. There are some who would have us believe that all prisoners are mentally affected, in fact they urge that the mere fact of their committing crime is a proof of this. There are others, who, whilst not going this length, yet put the number at a very high figure. One well known writer recently alleged in the daily press that probably 40 per cent. of our criminals are mentally defective. A well known alienist writing to the "Times" some years ago stated that at least 20 per cent. of all police court cases belonged to the class of mental defectives. The Medical Investigators appointed by the Royal Commission for the care and control of the feeble-minded, after visiting several prisons and having seen some 2,553 prisoners, estimated the number as mentally defective at 10·28 per cent. This is again a higher rate than is generally returned by the prison authorities as the number of mentally defective persons amongst the prison population (irrespective of those certifiably insane who are obviously unfit to be at large), _viz._, 3 per cent. "Here at once is a wide divergence of opinion and the reason for the great discrepancy is that so much depends on the view that is taken as to the degree of mental deficiency which justifies an individual being regarded as "Feeble-minded." There is no hard and fast line of demarcation, as has been asserted, between feeble-mindedness and sanity, any more than there is between a great many cases of insanity and sanity; from the normal down to the lowest idiot, or dement, it is only the question of degree of deficiency of mental power. This was pointed out by the Departmental Committee on Defective and Epileptic Children as far back as 1898." "One of the Medical Investigators of the Royal Commission alleges that "the higher grade aments" are sometimes not recognised by the prison authorities, who are apt to think a man who works well and behaves well in prison must be normal. There is some truth, no doubt, in this, for in prison there is strict and close supervision, there is the daily routine and the absence of "stress," "alcohol" and "temptation," to which people are subject in the outer world; moreover, in many cases, their time in prison is very short and their true mental condition is masked by the condition in which they are received (as, for instance, under the influence of drink and deprivation) so that the medical officer very naturally hesitates before reporting them feeble-minded." The Mental Deficiency Act, 1913, came into operation on the 1st April 1914. It provides for three forms of supervision for defectives, _viz_:--State Institutions for defectives of dangerous or violent propensities, Certified Institutions, and Guardianship. The last named can be ignored in considering criminal defectives.