The foregoing observations merely indicate generally the direction in which the manifold activities of the Medical Prison Service are exercised. I have laid stress on the part played in the discernment and investigation of mental disorder. That the question of guilt is identical with the question of mental soundness is a commonplace not only with those who seek to analyse by scientific inquiry the mysterious and subtle working of the human mind, but with those who, working in the name of humanity, are forced by personal observation, unaided by science, to the conclusion that many whom the law strikes are not fully responsible for their actions, and are not justly punished. In the United States of America, where science and humanity march hand-in-hand in exploring prisons and places of punishment, and in surveying the whole field of crime, we find that practical steps have been taken by the establishment of criminal laboratories, as at Chicago and Boston, to classify offenders, especially the young, according to the nature and degree of their mental capacity for distinguishing right from wrong. There is nothing so elaborate as this in England, but this is not because public opinion is not keenly alive to the importance of the medical aspect of cases, but because it would not be disposed to admit that the causes of a criminal act are discoverable by physical observation, or by the precise research of a criminal or clinical laboratory. It would be the duty, and the pride, of any civilized State to maintain a high standard of medical work in Prisons: it is a question whether the establishment of criminal laboratories does more than illustrate the practical benefits to be derived from good and thorough medical work in prisons, and whether experimental psychology, with its instruments of precision for testing the human mind, is a really effective auxiliary for the Court of Law in deciding guilt. It may be of value, as a supplementary aid to such diagnosis as a conscientious Medical Officer would apply, and it could be used as a means to support and justify opinion, but it cannot, by itself, be a substitute for other methods of observation. Though public opinion in England is increasingly sensitive to degrees of responsibility, as affecting punishment of crime, it would be more disposed to place its faith in a medical man having experience of mental disease than in the conclusions drawn from the employment of the precise methods of experimental psychology alone. It is disposed to take the view expressed by no less an authority than Dr. Binet, which is to the effect that the complex phenomena of human action cannot be expressed in a few terse formulas,--"_c'est de la littérature: ce n'est pas de la science_." He inclines to the view that the essential characteristic of normal man is in the _direction_ of choice. The want of direction is due to a disordered _moral_ nature. Of this moral degeneracy little is known.