The most difficult thing in the study of man is to surprise him on the threshold of life, to meet him as he detaches himself from the tissues of the mother, in the guise of a cell seeking the mysterious contact of the fertilising element; to seize the moment in which that wondrous force containing potentially the whole story of an existence penetrates the chemical elements of the germ; to learn how, in the protoplasm of the first imperceptible nucleus, that marvellous activity awakes which only death will end. There is a comparatively long period at the very beginning of our existence in which the nature and differential properties of the tissues lie, so to speak, dormant in a crumb of protoplasm. Microscopists discover no difference between the cells of that primary tissue. The turbidness appearing on the whitish leaflet of the germ seems regulated from the beginning of the division of labour; at a few points the materials accumulate which are requisite for the transformation of the cells, as though these last, too much occupied in their prodigious activity of separating and multiplying, must find close at hand the materials which they need to make a man, without the delay of elaborating and preparing them before they introduce them into their body. Thus it has been found, that from the beginning sugar or glycogen, one of the most important substances in the composition of the muscles, is present in abundance. But up to this point, and even for many days afterwards, there is no indication, no possible recognition, even of a rough outline of a human form. And yet in this confusion of atoms we exist. Here our passions lie sleeping; on this whitish leaflet are written in undecipherable characters those links of heredity which connect us with our family and with past generations. As from the scarcely visible germ in the heart of the acorn the majestic oak will spring to reign over the forest, so from this indistinct cellular mass a being will be formed to represent in his microcosm the whole history of the human race, with its fears, diseases, instincts, passions, its hate, vileness, and grandeur. The terrible legend of curses blasting the innocence of unborn babes, the blessings cast forth into the future for the enjoyment of generations yet to come, are not wholly a foolish fable. Destiny loads each one of us with a fatal inheritance. Though we were abandoned in the forest, imprisoned in the dungeon of a tower, without a guide, without example, without light, there yet would awake in us, like a mysterious dream, the experience of our parents and our earliest ancestors. What we call instinct is the voice of past generations reverberating like a distant echo in the cells of the nervous system. We feel the breath, the advice, the experience of all men, from those who lived on acorns and struggled with the wild beasts, dying naked in the forests, down to the virtue and toil of our father, to the fear and love of our mother. II