Page:The Harvard Classics Vol. 51; Lectures.djvu/109

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work of many trained observers, led to the recognition of the cell as the morphological element of living things, with this as a basis, to the systematic development of the whole of histology; and so to a new embryology and pathology. Thus the names of Schleiden, Schwann, Von Baer, and Virchow have become immortal.

Rigid ideas based upon classification, which had long tottered before the assaults of Lamarck, Goethe, Erasmus Darwin, Geoffroy Saint-Hilaire, and others, finally fell before Charles Darwin's[1] triumphant conception of natural selection by survival of the fittest, perhaps the most influential idea upon the thought of his time that has ever been put forward by any man. Out of this have grown the study of heredity and, partly through the efforts of Darwin's cousin, Francis Galton, a new doctrine of perfectibility.

In another department of biology, the study of the phenomena of digestion, fermentation, putrefaction, etc., after varying fortunes, culminated in Pasteur's[2] discovery of the role of micro-organisms, confirming the views of Redi and Swammerdam against spontaneous generation. The results of Pasteur's discoveries have now swelled into the greatest material benefit ever conferred by one man upon his fellows. They have led to antitoxins, immunity, and the greater part of preventive medicine, as well as to antisepsis and asepsis (Lister),[3] and so to the principal triumphs of surgery.


Experimental methods, guided by mechanics, optics, heat, electricity, and chemistry, were now systematically applied to physiology, then to psychology, and, with the help of the cellular hypothesis and the sciences of embryology, evolution, heredity, immunity, etc., they have transformed biology.

Everywhere, if other mathematical methods fail, the statistical method is being applied and in suitable cases, as, for example, life insurance, with great success; thus literally bringing order out of chaos.

Meantime the world has learned that science pays. Accordingly

  1. "Origin of Species," in H. C., xi.
  2. H. C., xxxviii, 273-382.
  3. H. C., xxxviii, 257.