Except, however, where the ends of justice seem to require a special departure from the rule, isolation, that is, the complete separation of prisoners one from the other, was strictly maintained at Mazas. All the arrangements of the prison were based upon this idea--the private boxes of the _parloir_, or visiting cell; the separate compartments in the exercising yards, where each prisoner ranges like a beast in a menagerie up and down a narrow cage, in shape like a wedge cut out of a plum cake; all are meant to secure the great end. Even the method of conducting divine service was such that every prisoner could attend mass without seeing or being seen by his neighbors or leaving his own cell. This was effected by establishing an altar on the top of the office in the _rond point_, or central hall. The _aumonier_, or prison chaplain, who officiated here, could be seen from every cell in the prison. All the doors were bolted ajar by a very ingenious arrangement. The long steel bar which usually secured the cell was shot for the time being into a ring projecting from the casing of the door, and thus a long, narrow aperture was left facing the altar, but only a few inches wide. This system no doubt prevented the intercommunication possible in an open chapel; yet, while this can be reduced to a minimum where discipline is strong and supervision effective, the prisoner alone in his cell was under no surveillance at all. He could behave just as it suited him. A close observer, Maxime du Camp, examined thirty-three cells, and observed what their inmates were doing while mass was being said. Three only were reading their missals and following the priest; one was on his knees; one was standing uncovered, looking towards the altar; one had opened his prayer book, but for choice was looking at the _Magasin Pittoresque_; one other, with his head buried deep in his arms, was shaken by a paroxysm of tears.