10 62. The medical services of the institution shall seek to detect and shall treat any physical or mental illnesses or defects which may hamper a prisoner's rehabilitation. All necessary medical, surgical and psychiatric services shall be provided to that end. 63. (1) The fulfilment of these principles requires individualization of treatment and for this purpose a flexible system of classifying prisoners in groups; it is therefore desirable that such groups should be distributed in separate institutions suitable for the treatment of each group. (2) These institutions need not provide the same degree of security for every group. It is desirable to provide varying degrees of security according to the needs of different groups. Open institutions, by the very fact that they provide no physical security against escape but rely on the self-discipline of the inmates, provide the conditions most favourable to rehabilitation for carefully selected prisoners. (3) It is desirable that the number of prisoners in closed institutions should not be so large that the individualization of treatment is hindered. In some countries it is considered that the population of such institutions should not exceed five hundred. In open institutions the population should be as small as possible. (4) On the other hand, it is undesirable to maintain prisons which are so small that proper facilities cannot be provided. 64. The duty of society does not end with a prisoner's release. There should, therefore, be governmental or private agencies capable of lending the released prisoner efficient after-care directed towards the lessening of prejudice against him and towards his social rehabilitation. Treatment 65. The treatment of persons sentenced to imprisonment or a similar measure shall have as its purpose, so far as the length of the sentence permits, to establish in them the will to lead law-abiding and self-supporting lives after their release and to fit them to do so. The treatment shall be such as will encourage their self-respect and develop their sense of responsibility. 66. (1) To these ends, all appropriate means shall be used, including religious care in the countries where this is possible, education, vocational guidance and training, social casework, employment counselling, physical development and strengthening of moral character, in accordance with the individual needs of each prisoner, taking account of his social and criminal history, his physical and mental capacities and aptitudes, his personal temperament, the length of his sentence and his prospects after release. (2) For every prisoner with a sentence of suitable length, the director shall receive, as soon as possible after his admission, full reports on all the matters referred to in the foregoing paragraph. Such reports shall always include a report by a medical officer, wherever possible qualified in psychiatry, on the physical and mental condition of the prisoner. (3) The reports and other relevant documents shall be placed in an individual file. This file shall be kept up to date and classified in such a way that it can be consulted by the responsible personnel whenever the need arises. Classification and individualization 67. The purposes of classification shall be: ( a ) To separate from others those prisoners who, by reason of their criminal records or bad characters, are likely to exercise a bad influence; ( b ) To divide the prisoners into classes in order to facilitate their treatment with a view to their social rehabilitation.