viewed in its light, the number of possible arrangements in the ovum and spermatozoön grows into immensity. If we could imagine the head of a spermatozoön as large as the Great Eastern, and the space represented by it filled with a wheel-work as fine as that of the smallest lady's watch, our figure would still be far from giving any kind of a representation of the ultimate division of matter. It is thus clear that the head of a spermatozoön affords space and opportunity for the endlessly numerous arrangements and various motions on which the innumerable types and properties, with which this apparently so simple organism is charged, finally depend. It may then, at all events, be conceived that parental dyscrasies communicate themselves through the blood to the germs in the testicles and ovaries. But now let a group of ganglion-cells in the brain, if we may speak thus, be played upon to a certain molecule-dance-figure. The blood can not be changed by that. Consequently, the threads of the plexus spermaticus internus must so work upon the semen-cells in the seminal canal, the egg-cells in the after-growing Graafian pustules, that each act of exercise in the course of growth leaves its mark on the egg or on the spermatozoön, and that it is followed after years by the natural culmination of the same molecule-dance-figure in the corresponding group of ganglion cells in the man or animal that has grown up out of that egg, or with the aid of that spermatozoön. How the plexus spermaticus internus, the connection of which with the brain is only of the loosest character, brings this to pass, can not be found out. The conditions are no more favorable for the comprehension of the kinds of exercise resting upon nutritive and formative stimulation.
As we have already pointed out, it appears that we might, in order to verify the transmission of acquired properties, invoke the example of hereditary diseases, from which our ancestors were in all probability free, which chiefly visit more highly developed manhood, and the transmission of which consequently resembles the transmission of acquired properties. Still, we may question whether the first epileptic attack, the first migraine, followed injuries which came upon a sound adult, or whether the foundation for them was not laid in the egg or the spermatozoön out of which the first sufferer grew. There remains, for the confirmation of this view—we will be honest—the transmission of acquired peculiarities, an hypothesis drawn solely from the facts illustrating it, yet quite obscure in itself, which receives only doubtful light through Darwin's "pangenesis."
I believe now, gentlemen, that I have justified the expression with which I introduced to you my intention to speak of exercise—that is, that it deserved a place in the scientific order of the day; yet I need not say explicitly how far I am from entertaining the thought that I have contributed anything essential to the fulfillment of that object. I consider that I have succeeded no further than more sharply to define the eventual phylogenetic office of exercise and the direction of the
