Among the masters of biological science, Cuvier, V. Baer, Agassiz, and R. Owen may be named, as among those who have set the highest value on the principle of finality. The essay on Classification of Agassiz, and the various essays which Von Baer has published at different times, on what he calls "Zielstrebigkeit," are specially important.
Note XVIII., page [148].
Evidences of Design in Organisms.
"The savants are generally too much disposed to confound the doctrine of final cause with the hypothesis of an invisible force acting without physical means, as a deus ex machinâ. These two hypotheses, far from reducing themselves the one to the other, are in explicit contradiction; for he who says design says at the same time means, and, consequently, causes adapted to produce a certain effect. To discover this cause is by no means to destroy the idea of design; it is, on the contrary, to bring to light the condition, sine quâ non, of the production of the end. To make clear this distinction we cite a beautiful example, borrowed from M. Claude Bernard. How does it happen, says this eminent physiologist, that the gastric juice, which dissolves all aliments, does not dissolve the stomach itself, which is of precisely the same nature as the aliments with which it is nourished? For a long time the vital force was supposed to intervene—that is to say, an invisible cause which, in some way, suspended the properties of the natural agents, to prevent their producing their necessary effects. The vital force would, by a sort of moral veto, forbid the gastric juice to touch the stomach. We see that this would be a real miracle. Everything is explained when we know that the stomach is lined with a coating or varnish which is not attacked by the gastric juice, and which protects the walls which it covers. Who does not see that in refuting the omnipotence of the vital force, very far from having weakened the principle of finality, we have given to it a wonderful support? What could the most perfect art have done to protect the walls of the stomach, but invent a precaution similar to that which exists in reality? And how surprising it is that an organ destined to secrete and use an agent most destructive to itself, is found armed with a protective tunic, which must have always coexisted with it, since otherwise it would have been destroyed before having had time to procure for itself this defence—which excludes the hypothesis of long gropings and happy occurrences."—Janet, 'Final Causes and Contemporaneous Physiology,' Presb. Quart. Rev., April 1876.
Professor Tyndall gives a very graphic description of the combination of remarkable arrangements by which the human ear is fitted to be an organ of hearing. I quote from it the following words, and connect with them some striking observations of Max Müller. "Finally, there is in the labyrinth a wonderful organ, discovered by the Marchese Corti, which is to all appearance a musical instrument, with its chords so stretched as to accept vibrations of different periods, and transmit them to the nerve-filaments which traverse the organ. Within the ears of men, and without their knowledge or contrivance, this lute of 3000 strings has existed for ages, accepting the music of the outer world, and rendering it fit for reception by the brain. Each musical tremor which falls upon this organ selects from its tensioned fibres the one appropriate to its own pitch, and throws that fibre into unisonant vibration. And thus, no matter how complicated the motion of the external air may be, those microscopic strings can analyse it and reveal the constituents of which it is composed."—On Sound, p. 325. "What we hear when listening to a chorus or a symphony is a commotion of elastic air, of which the wildest sea would give a very inadequate image. The lowest tone which the ear perceives is due to about 30 vibrations in one second, the highest to about 4000. Consider, then, what happens in a presto, when thousands of voices and instruments are simultaneously producing waves of air, each wave crossing the other, not only like the surface waves of the water, but like spherical bodies, and, as it would seem, without any perceptible disturbance; consider that each tone is accompanied by secondary notes, that each instrument has its peculiar timbre, due to secondary vibrations; and, lastly, let us remember that all this cross-fire of waves, all this whirlpool of sound, is moderated by laws which determine what we call harmony, and by certain traditions or habits which determine what we call melody—both these elements being absent in the songs of birds—that all this must be reflected like a microscopic photograph on the two small organs of hearing, and there excite not only perception, but perception followed by a new feeling even more mysterious, which we call either pleasure or pain;—and it will be clear that we are surrounded on all sides by miracles transcending all we are accustomed to call miraculous."—Science of Language, second series, p. 115.
The structure of the eye has often been described as an evidence of design. There is an extremely interesting comparison of it with the photographic camera in Le Conte's 'Religion and Science,' pp. 20-33.
The whole reading public knows the masterly chapter on "The Machinery of Flight" in the Duke of Argyll's 'Reign of Law.'
Note XIX., page [149].