Page:Popular Science Monthly Volume 4.djvu/65

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N human science there is many a ground of self-satisfaction and of pride for the mind, but there are at the same time reasons for humility and bitter disappointment. Notwithstanding the strenuous efforts and the protracted meditations of the legions of investigators who have gone before us, Nature still has abysses dark and deep before which the keenest sight becomes blindness, courage changes into fear, and assurance into despondency. When we strive to throw some light into these mysterious gulfs, the light does but reveal to us the spectres of our own ignorance, and all that we carry away from the vain attempt is a renewed consciousness of our weakness and indigence. It were wise for us to carry away something more, viz., a useful lesson. Indeed, there is nothing that is better fitted to teach us modesty and patience, to cool down presumptuous ardor, and to put to shame overweening temerity, than the study of those phenomena which Providence would seem to have devised for the express purpose of baffling man's curiosity. And yet many there are who pretend to ignore the wonderful and complex phenomena which occur in regions inaccessible to sight or sense, and who stubbornly question the existence of invisible activities and insensible forces. Such is the fatal skepticism against which we must cite the testimony of the sphinxes that occupy our attention now. The lesson is all the more impressive, inasmuch as, by strange contrast, these questions, so refractory to all manner of theoretic explanation, are precisely the ones with which our empirical acquaintance is fullest. Here a knowledge of effects seems in no wise to pave the way to a knowledge of causes.

These remarks have a special application to the subject of heredity. It is an ascertained fact that the ovum contains in its seemingly homogeneous substance not only the anatomical structure of the individual that is to spring from it, but also his temperament, character, aptitudes, sentiments, and thoughts. The parents place in this molecule the future of an existence which is nearly always the counterpart of themselves physiologically, oftentimes pathologically, and in many instances psychologically. Such are the results of the latest studies into this amazing vital economy; and these we purpose laying before our readers.

Heredity is that biological law in virtue of which living beings tend to transmit to their descendants a certain number of their own characteristic traits. It is a very nice question to decide whether we must class under heredity the transmission of the anatomical forms