"Ordinary individuals, and even scientific observers, are apt to regard prisons, especially those in which the cellular system prevails, as mute and paralytical organisms, deprived of speech and action, because silence and immobility have been imposed on them by law. Since, however, no decree, even when backed up by physical force, avails against the nature of things, these organisms speak and act, and sometimes manifest themselves in brutal assaults and murders; but as always happens when human needs come into conflict with laws, all these manifestations are made in hidden and subterranean ways. Walls, drinking-vessels, planks of the prisoners' beds, margins of books, medicine wrappers, and even the unstable sands of the exercise-grounds, and the uniform in which the prisoner is garbed, supply him with a surface on which to imprint his thoughts and feelings." With this paragraph my father begins the introduction to his book _Prison Palimpsests_, a collection of inscriptions and documents revealing the inmost thoughts of prisoners. In the first part, these inscriptions are classified under different headings: opinions on prison life, penalties, morality, women, etc., and according to the surface on which they are inscribed--books, walls, pitchers, clothing, paper, etc. For the psychologist and the student of degenerate types of humanity, this collection is of the greatest interest. The inscriptions are followed by a series of poems, autobiographies, and letters written by intending suicides, and criminals immediately before their execution. The comments made by criminals on the margins of books belonging to the prison library are especially interesting, because they enable the student to compare the effect produced on criminals by certain works with the impressions of normal individuals. The poems written by prisoners are equally interesting, since, like popular songs, they represent the intimate expression of the poet's desires and aspirations. In the second part, these prison inscriptions are compared with the remarks commonly found scribbled in the streets, on school benches, and on the walls of public buildings of all kinds--courts of justice, places of worship, and even those edifices in which the legislation of the State is framed. All the inscriptions are classified according to the sentiments they express and the sex of the writer, distinction being made between the writings of prisoners and those of the ordinary public. The book closes with practical suggestions regarding the use to which similar collections might be put, as critical hints on the present methods of dealing with criminals and as an aid in investigating the characters of accused persons.