The exceptionally acute psychiatrist Meynert shows[118] how physiognomics depends on irradiation and parallel images. He shows what a large amount of material having physiognomical contents we keep in mind. Completely valueless as are the fixed forms by which mankind judges the voluntary acts of its individual members, they point to the universal conclusion that it is proper to infer from the voluntary acts of a person whose features correspond to those of another the voluntary acts of the other. One of Hans Virchow’s very detailed physiognomical observations concerning the expression of interest in the eyes by means of the pupil, has very considerable physiognomical value. The pupil, he believes, is the gate through which our glance passes into the inner life of our neighbor; the psychical is already close at hand with the word “inner.” How this occurs, why rather this and not another muscle is innervated in the development of a certain process, we do not know, but our ignorance does not matter, since ultimately a man might split his head thinking why we do not hear with our eyes and see with our ears. But to some extent we have made observable progress in this matter. As far back as 1840 J. Müller[119] wrote: “The reasons are unknown why various psychoses make use of different groups of nerves or why certain facial muscles are related to certain passions.” Gratiolet[120] thought it necessary forty years ago to deny that muscles were developed merely for the purpose of expression. Almost contemporaneously Piderit knew that expressive muscular movements refer partly to imaginary objects and partly to imaginary sense impressions. In this fact lies the key to the meaning of all expressive muscular movements. Darwin’s epoch-making book on the expressions of the emotions finally established the matter so completely and firmly, that we may declare ourselves in possession of enough material for our purpose to make it possible to carry our studies further. The study of this book of Darwin’s I believe absolutely necessary to each criminalist--for he meets in every direction, expositions and explanations that are related to cases he has already experienced in practice or is sure to experience. I present here only a few of Darwin’s most important notes and observations in order to demonstrate their utility for our purpose.