Every unexpected occurrence was pressed into service. Witness the following anecdote: “One day my horse was much frightened at a drilling machine, covered by a tarpaulin and lying on an open field. He raised his head so high that his neck became almost perpendicular; and this he did from habit, for the machine lay on a slope below, and could not have been seen with more distinctness through the raising of the head; nor if any sound had proceeded from it could the sound have been more distinctly heard. His eyes and ears were directed intently forwards; and I could feel through the saddle the palpitations of his heart. With red, dilated nostrils, he snorted violently, and whirling round, would have dashed off at full speed had I not prevented him.”
We see, too, in this book the results of Darwin’s extensive reading. The novelists are laid considerably under contribution, their power of describing expressive signs of emotion being particularly appreciated. Dickens, Walter Scott, Mrs. Oliphant, and Mrs. Gaskell are among the novelists quoted; while the author of Job, Homer, Virgil, Seneca, Shakespeare, Lessing, Sir Joshua Reynolds, and many other deceased writers, illustrate the subject. The living authorities—scientific men, travellers, doctors—referred to for facts are exceedingly numerous, including Sir James Paget, Professor Huxley, Mr. Herbert Spencer, Sir J. Crichton Browne, Sir Samuel Baker, Sir Joseph Lister, Professors Cope and Asa Gray, and many others.
One of the most interesting chapters in the book is that dealing with blushing. It is shown to depend on self-attention, excited almost exclusively by the opinion of others. “Every one feels blame more acutely than praise. Now, whenever we know, or suppose, that others are depreciating our personal appearance, our attention is strongly drawn towards ourselves, more especially to our faces.” This excites the nerve centres receiving sensory nerve for the face, and in turn relaxes the blood capillaries, and fills them with blood. “We can understand why the young are much more affected than the old, and women more than men, and why the opposite sexes especially excite each others’ blushes. It becomes obvious why personal remarks should be particularly liable to cause blushing, and why the most powerful of all the causes is shyness; for shyness relates to the presence and opinion of others, and the shy are always more or less self-conscious.”
One great result made clear by Darwin is that the muscles of expression have not been created or developed for the sake of expression only, and that every true or inherited movement of expression had some natural or independent origin. All the chief expressions are proved to be essentially the same throughout the world, which is an additional argument for man being descended from one stock. We cannot refrain from admiring the tone of the pages which close the book, describing as they do the probable expressions of our early ancestors, their utility, the value of differences of physiognomy, and the desirability or otherwise of repressing signs of emotion. The subject, says the author, “deserves still further attention, especially from any able physiologist;” and so simply ends a volume of surpassing human interest, a text-book for novelists and students of human nature, a landmark in man’s progress in obedience to the behest “Know thyself.”
To fully measure the merit of one so far elevated above ordinary men is almost impossible; rather is it desirable to recognise the undeniable greatness of a great man, and learn all that is possible from him. An undoubted authority in mental science, however, has given a judgment on Darwin’s services to that science, which it is right to quote: “To ourselves it almost seems one of the most wonderful of the many wonderful aspects of Mr. Darwin’s varied work that by the sheer force of some exalted kind of common-sense, unassisted by any special acquaintance with psychological method, he should have been able to strike, as it were, straight down upon some of the most important truths which have ever been brought to light in the region of mental science.”[12] These truths are specified as the influence of natural selection in the formation of instinct, in the “Origin of Species;” the evolution of mind and of morals, in the “Descent of Man,” considered by the late Professor Clifford as containing the simplest and clearest and most profound philosophy that was ever written on the subject; and the evolution of expression in the book described in this chapter. Thus, says Mr. Romanes, in respect both of instincts and intelligence, the science of comparative psychology may be said to owe its foundation to Darwin.
[ CHAPTER IX.]
IN 1875 appeared another great work from the master’s pen, “Insectivorous Plants,” which was destined to place in a yet more striking light the many-sidedness and fertility of his mind. As usual Darwin tells us that this work dated from many years back. “During the summer of 1860,” he says, “I was surprised by finding how large a number of insects were caught by the leaves of the common sun-dew (Drosera rotundifolia) on a heath in Sussex. I had heard that insects were thus caught, but knew nothing further on the subject. I gathered by chance a dozen plants, bearing fifty-six fully expanded leaves, and on thirty-one of these dead insects or remnants of them adhered.” Here was the germ of something, the discoverer scarcely knew what. It was evident to him that the little sun-dew was excellently adapted for catching insects, and that the number of them thus slaughtered annually must be enormous. What bearing might this have upon the problem of the struggle for existence?
A masterly series of experiments was forthwith set on foot, with the result of proving that sun-dews and a number of other plants obtain the bulk of their nourishment by catching, killing, and digesting insects. They may be called truly carnivorous plants. What an unexpected reversal this was of the order of things hitherto believed to prevail universally. Animals live on other animals or on plants. Here were plants living on animals, and keeping down their number. Moreover, without a nervous system, the action of the parts of a sun-dew leaf was proved to be as apparently purposive as the combined action of the limbs of an animal. Without a stomach, the sun-dew poured forth a digestive fluid as effective in extracting and fitting the nutritious matter of the insect for its own purposes as that of an animal. Without sensory nerve-endings, there was a percipient power in the sun-dew which recognised instinctively and at once the non-nutritious nature of various objects, and which responded to the most delicate chemical stimuli and to the minutest weights.
We cannot describe the little sun-dew better than in Darwin’s own words: “It bears from two or three to five or six leaves, generally extended more or less horizontally, but sometimes standing vertically upwards. The leaves are commonly a little broader than long. The whole upper surface is covered with gland-bearing filaments, or tentacles as I shall call them from their manner of acting. The glands were counted on thirty-one leaves, but many of these were of unusually large size, and the average number was 192; the greatest number being 260, and the least 130. The glands are each surrounded by large drops of extremely viscid secretion, which, glittering in the sun, have given rise to the plant’s poetical name of the sun-dew.”