And when we remember the enormous number of crimes and offences which are not punished, for lack or inadequacy of evidence, and the frequency of trials which are based solely on circumstantial hints, it is easy to see the practical utility of the primary connection between criminal sociology and penal procedure. The practical application of anthropometry to the identification of criminals, and to the question of recidivism, which was begun in Paris by M. Bertillon, and subsequently adopted by almost all the states of Europe and America, is too familiar to need description. It will be sufficient to recall the modifications of Bertillon's system by Anfosso, with the actual collection of anthropometric data, and their inclusion in the ordinary records of justice. Thus the sphygmographic data on the circulation of the blood, which reveal the inner emotions, in spite of an outward appearance of calm or indifference, have already served to show that a person accused of theft was not guilty of it, but that he was on the contrary guilty of another theft, of which he had not been so much as suspected. On another occasion they established the innocence of a man condemned to death. We shall have more speaking and frequent illustrations when these inquiries have been placed regularly at the service of criminal justice. The sphygmograph may also be useful in the diagnosis of simulated disease, after the example set M. Voisin in the case of a sham epileptic in Paris, ``whose sphygmographic lines have no resemblance to those of true epileptics before and after a fit, and <168>only resemble those produced by normal persons after a violent gesticulation.'' As for the possible utilisation of hypnotism, we must be cautious before we draw any legal conclusions from it; but it cannot be questioned that this is a valuable source of scientific aid in the systematic collection of criminal evidence. But, for the present, the most certain and profitable aids in the collection of evidence are those afforded by the organic and psychical characteristics of criminals. In my study on homicide I reckoned up many psychological and psycho-pathological symptoms which characterise the murderer, the homicidal madman, and the homicide through passion. And in my professional practice I have often found by experience that there is a great suggestive efficacy in these psychological symptoms in regard to the conduct of a criminal, before, during, and after a crime; and it is important to bring this knowledge scientifically before detectives and judges.