MEMCAL SCHOOL
L1IIBMA150'

THE GILBERT V. HAMILTON

MEMORIAL LIBRARY

GIFT OF MARY S. HAMILTON

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BIOLOGY
AND ITS MAKERS

With Portraits and Other Illustrations

\ BY

WILLIAM A. lLOCY, Ph.D., Sc.D,

Prqfeisor in Northivestern Uni-versity

THIRD EDITION, REVISED

L^. i

NEW YORK

HENRY HOLT AND COMPANY

1915

Copyright, 1908,

BY

HENRY HOLT AND COMPANY

Published June, 1908

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,• ~

To

MY GRADUATE STUDENTS

Who have worked by my side in the Laboratory

Inspired by the belief that those who seek shall find

This account of the findings of some of

The great men of biological science

Is dedicated by

The Author

C)du^'>

PREFACE

The writer is annually in receipt of letters from students,
teachers, ministers, medical men, and others, asking for in-
formation on topics in general biology, and for references to
the best reading on that subject. The increasing frequency
of such inquiries, and the wide range of topics covered, have
created the impression that an untechnical account of the
rise and progress of biology would be of interest to a con-
siderable audience. As might be surmised, the references
most commonly asked for are those relating to different
phases of the Evolution Theory; but the fact is usually over-
looked by the inquirers that some knowledge of other features
of biological research is essential even to an intelligent com-
prehension of that theory.

In this sketch I have attempted to bring under one view
the broad features of biological progress, and to increase the
human interest by writing the story around the lives of the
great Leaders. The practical execution of the task resolved
itself largely into the question of what to omit. The number
of detailed researches upon which progress in biology rests
made rigid selection necessary, and the difficulties of separat-
ing the essential from the less important, and of distinguish-
ing between men of temporary notoriety and those of endur-
ing fame, have given rise to no small perplexities.

The aim hks been kept in mind to give a picture suffi-
ciently diagrammatic not to confuse the general reader, and
it is hoped that the omissions which have seemed necessar)^
will, in a measure, be compensated for by the clearness of
the picture. References to selected books and articles have

VI PREFACE

been given at the close of the volume, that will enable readers
who wish fuller information to go to the best sources.

The book is divided into two sections. In the first are
considered the sources of the ideas — except those of organic
evolution — that dominate biology, and the steps by which
they have been molded into a unified science. The Doc-
trine of Organic Evolution, on account of its importance,
is reserved for special consideration in the second section.
This is, of course, merely a division of convenience, since
after its acceptance the doctrine of evolution has entered
into all phases of biological progress.

The portraits with which the text is illustrated embrace
those of nearly all the founders of biology. Some of the
rarer ones are unfamiliar even to biologists, and have been
discovered only after long search in the libraries of Europe
and America.

An orderly account of the rise of biology can hardly fail
to be of service to the class of inquirers mentioned in the
opening paragraph. It is hoped that this sketch will also
meet some of the needs of the increasing body of students
who are doing practical work in biological laboratories. It is
important that such students, in addition to the usual class-
room instruction, should get a perspective view of the way
in which biological science has come into its present form.

The chief purpose of the book will have been met if I
have succeeded in indicating the sources of biological ideas
and the main currents along which they have advanced, and
if I have succeeded, furthermore, in making readers ac-
quainted with those men of noble purpose whose work has
created the epochs of biological history, and in showing that
there has been continuity of development in biological
thought.

Of biologists who may examine this work with a critical
purpose, I beg that they will think of it merely as an outline

PREFACE vu

sketch which does not pretend to give a complete history of
biological thought. The story has been developed almost
entirely from the side of animal life; not that the botanical
side has been underestimated, but that the story can be told
from either side, and my first-hand acquaintance with botan-
ical investigation is not sufhcient to justify an attempt to es-
timate its particular achievements.

The writer is keenly aware of the many imperfections in
the book. It is inevitable that biologists with interests in
special fields will miss familiar names and the mention of
special pieces of notable work, but I am drawn to think that
such omissions will be viewed leniently, by the consideration
that those best able to judge the shortcomings of this sketch
will also best understand the difficulties involved.

The author wishes to acknowledge his indebtedness to
several publishing houses and to individuals for permission
to copy cuts and for assistance in obtaining portraits. He
takes this opportunity to express his best thanks for these
courtesies. The parties referred to are the director of the
American Museum of Natural History; D. Appleton & Co.;
P. Blakiston's Sons & Co.; The Macmillan Company;
The Open Court Publishing Company; the editor of the
Popular Science Monthly \ Charles Scribner's Sons; Pro-
fessors Bateson, of Cambridge, England; Conklin, of Phila-
delphia; Joubin, of Rennes, France; Nierstrasz, of Utrecht,
Holland ; Newcombe, of Ann Arbor, Michigan ; Wheeler and
E. B. Wilson, of New York City. The editor of the Popu-
lar Science Monthly has also given permission to reprint the
substance of Chapters IV and X, which originally ap-
peared in that publication.

W. A. L.

Northwestern University,
Evanston, III., April, 1908.

PREFACE TO THE THIRD REVISED
EDITION

It is a feature of scientific knowledge to be always improv-
ing, and, owing to advances since the publication of the
earlier editions, many of the matters dealt with in this book
appear in a new and clearer light. But since the book aims
primarily to point out the epochs of advancement as well as
to depict the conditions under which, and the spirit in which
advances have been consummated, the subject matter of the
text does not quickly become obsolete.

While retaining substantially its original form, some altera-
tions have been made: several pages have been rewritten to
convey more clearly the meaning, as in reference to Mendel's
discovery, and some additions have been introduced, as com-
ments on isolation and orthogenesis as factors of organic
evolution. The important contributions of Fritz Schaudinn
have been noted and the discussion of the antiquity of man
has been considerably extended. Several new portraits have
been substituted for those of the earlier editions and the por-
trait of Schaudinn has been added.

W. A. L.

March, 1915.

CONTENTS

PART I

The Sources of Biological Ideas Except Those of
Organic Evolution

CHAPTER I

PAGE

An Outline of the Rise of Biology and of the Epochs in its

History, 3

Notable advances in natural science during the nineteenth century, 3.
Biology the central subject in the history of opinion regarding
life, 4. It is of commanding importance in the world of science,
5. Difficulties in making its progress clear, 5. Notwithstanding
its numerous details, there has been a relatively simple and
orderly progress in biology, 6. Many books about the facts of
biology, many excellent laboratory manuals, but scarcely any
attempt to trace the growth of biological ideas, 6. The growth
of knowledge regarding organic nature a long story full of human
interest, 7. The men of science, 7. The story of their aspira-
tions and struggles an inspiring history, 8. The conditions under
which science developed, 8. The ancient Greeks studied nature
by observation and experiment, but this method underwent
eclipse, 9. Aristotle the founder of natural history, 9. Science
before his day, 9, 10. Aristotle's position in the development of
science, 11. His extensive knowledge of animals, 12. His scien-
tific writings, 13. Personal appearance, 13. His influence, 15.
Pliny: his writings mark a decline in scientific method, 16. The
arrest of inquiry and its effects, 17. A complete change in the
mental interests of mankind, 17. Men cease to observe and in-
dulge in metaphysical speculation, 18. Authority declared the
source of knowledge, 18. The revolt of the intellect against these
conditions, 19. The renewal of observation, 19, The beneficent
results of this movement, 20. Enumeration of the chief epochs
in biological history: renewal of observation, 20; the overthrow
of authority in science, 20. Harvey and experimental investiga-

CONTENTS

PAGE

tion, 20; introduction of microscopes, 20; Linnaeus, 20; Cuvier,
20; Bichat, 21; Von Baer, 21; the rise of physiology, 21; the
beginnings of evolutionary thought, 21; the cell-theory, 21; the
discovery of protoplasm, 21.

CHAPTER II

Vesalius and the Overthrow of Authority in Science, . . 22

Vesalius, in a broad sense, one of the founders of biology, 22. A pic-
ture of the condition of anatomy before he took it up, 23. Galen:
his great influence as a scientific writer, 24. Anatomy in the
Middle Ages, 24. Predecessors of Vesalius: Mundinus, Beran-
garius, Sylvius, 26. Vesalius gifted and forceful, 27. His im-
petuous nature, 28. His reform in the teaching of anatomy, 28.
His physiognomy, 30. His great book (1543), 32. A descrip-
tion of its illustrations, 32, ^;^. Curious conceits of the artist, 34.
Opposition to Vesalius: curved thigh bones due to wearing tight
trousers, the resurrection bone, 34, 35. The court physician, 36.
Close of his life, 36. Some of his successors: Eustachius and
Fallopius, 37. The especial service of Vesalius: he overthrew
dependence on authority and reestablished the scientific method
of ascertaining truth, 38.

CHAPTER III

William Harvey and Experimental Observation, . . .39

Harvey's work complemental to that of Vesalius, 39. Their com-
bined labors laid the foundations of the modern method of in-
vestigating nature, 39. Harvey introduces experiments on living
organisms, 40. Harvey's education, 40. At Padua, comes
under the influence of Fabricius, 41. Return to England, 42.
His personal quahties, 42-45. Harvey's writings, 45. His great
classic on movement of the heart and blood (1628), 46. His
demonstration of circulation of the blood based on cogent rea-
soning; he did not have ocular proof of its passage through
capillaries, 47. Views of his predecessors on the movement of
the blood, 48. Servetus, 50. Realdus Columbus, 50. Caesal-
pinus, 51. The originality of Harvey's views, 51. Harvey's
argument, 51. Harvey's influence, 52. A versatile student;
work in other directions, 52. His discovery of the circulation
created modern physiology, 52. His method of inquiry became
a permanent part of biological science, 53.

CONTENTS XI

PAGE

CHAPTER IV

The Introduction of the Microscope and the Progress of Inde-
pendent Observation, 54

The pioneer microscopists: Hooke and Grew in England; Malpighi
in Italy and Swammerdam and Leeuwenhoek in Holland, 54.
Robert Hooke, 5 5 . His microscope and the micrographia ( 1 665 ) ,
56. Grew one of the founders of vegetable histology, 56. Mal-
pighi, 1 628-1 694, 58. Personal qualities, 58. Education, 60.
University positions, 60, 61. Honors at home and abroad, 61.
Activity in research, 62. His principal writings: Monograph
on the silkworm, 63; anatomy of plants, 66; work in embry-
ology, 66. Jan Swammerdam, 1 637-16S0, 67. His temperament,
67. Early interest in natural history, 68. Studies medicine, 68.
Important observations, 68. Devotes himself to minute anat-
omy, 70. Method of working, 71. Great intensity, 70. High
quality of his work, 72. The Biblia Natura, 73. Its publica-
tion delayed until fifty-seven years after his death, 73. Illustra-
tions of his anatomical work, 74-76. Antony van Leeuwenhoek,
1632-1723,77. A composed and better-balanced man, 77. Self-
taught in science, the effect of this showing in the desultory char-
acter of his observations, 77, 87. Physiognomy, 78. New bio-
graphical facts, 78. His love of microscopic observation, 80.
His microscopes, 81. His scientific letters, 83. Observes the
capillary circulation in 1686, 84. His other discoveries, 86.
Comparison of the three men: the two university -trained men
left coherent pieces of work, that of Leeuwenhoek was discursive,
87, The combined force of their labors marks an epoch, 88.
* The new intellectual movement now well under way, 88,

CHAPTER V

The Progress of Minute Anatomy, 89

Progress in minute anatomy a feature of the eighteenth century.
Attractiveness of insect anatomy. Enthusiasm awakened by the
delicacy and perfection of minute structure, 89. Lyonet, 1707-
1789, 90. Description of his remarkable monograph on the
anatomy of the willow caterpillar, 91. Selected illustrations,
92-94. Great detail — 4,041 muscles, 91. Extraordinary character
of his drawings, 90. A model of detailed dissection, but lacking
in comparison and insight, 92. The work of Reaumur, Roesel,

XU CONTENTS

PAGE

and De Geer on a higher plane as regards knowledge of insect life,
95. Straus-Diirckheim's monograph on insect anatomy, 96. Rivals
that of Lyonet in detail and in the execution of the plates, 99.
His general considerations now antiquated, 99. He attempted
to make insect anatomy comparative, 100. Dufour endeavors to
found a broad science of insect anatomy, 100. Newport, a very
skilful dissector, with philosophical cast of mind, who recognizes
the value of embryology in anatomical work, 100. Leydig starts
a new kind of insect anatomy embracing microscopic structure
(histology), 102. This the beginning of modern work, 102.
Structural studies on other small animals, 103. The discovery
of the simplest animals, 104. Observations on the microscopic
animalcula, 105. The protozoa discovered in 1675 by Leeuwen
hoek, 105. Work of O. F. Miiller, 1786, 106. Of Ehrenberg
1838, 107. Recent observations on protozoa, 109.

CHAPTER VI

LiNN^us AND Scientific Natural History,

Natural history had a parallel development with comparative anatomy,
no. The Physiologus, or sacred natural history of the Middle
Ages, no, III. The lowest level reached by zoology, in. The
return to the science of Aristotle a real advance over the Physiol-
ogus, 112. The advance due to Wotton in 1552, 112. Gesner,
1516-1565. High quahty of his Historia Animalium, 112-114.
The scientific writings of Jonson and Aldrovandi, 114. John
Ray the forerunner of Linnjeus, 115. His writings, 117. Ray's
idea of species, 117. Linnaeus or Linne, 118. A unique ser-
vice to natural history. Brings the binomial nomenclature into
general use, 118. Personal history, 119. Quality of his mind,
120. His early struggles with poverty, 120. Gets his degree in
Holland, 121. Publication of the 6'>'5tewa iVa/wr« in 1735, 121.
Return to Sweden, 123. Success as a university professor in Up-
sala, 123. Personal appearance, 125. His influence on natural
history, 125, His especial service, 126. His idea of species,
128. Summary, 129. Reform of the Linnaean system, 130-
138. The necessity of reform, 130. The scale of being, 131.
Lamarck the first to use a genealogical tree, 132. Cuvier's
four blanches, 132. Alterations by Von Siebold and Leuckart,
134-137. Tabularviewof classifications, 138. General biologi-
cal progress from Linnaeus to Darwin. Although details were
multiplied, progress was by a series of steps, 138. Analysis

CONTENTS xm

PAGE

of animals proceeded from the organism to organs, from organs
to tissues, from tissues to cells, the elementary parts, and finally
to protoplasm, 13Q-140. The physiological side had a par-
allel development, 140.

CHAPTER VII

CUVIER AND THE RiSE OF COMPARATIVE AnATOMY, . . . . I4I

The study of internal structure of living beings, at first merely de-
scriptive, becomes comparative, 141. Belon, 141. Severinus
writes the first book devoted to comparative anatomy in 1645,
143. The anatomical studies of Camper, 143. John Hunter,
144.. Personal characteristics, 145. His contribution to prog-
ress, 146. Vicq d'Azyr the greatest comparative anatomist
before Cuvier, 146-148. Cuvier makes a comprehensive study
of the structure of animals, 148. His birth and early education,
149. Life at the sea shore, 150. Six years of quiet study and
contemplation lays the foundation of his scientific career, 150.
Goes to Paris, 151. His physiognomy, 152. Comprehensiveness
of his mind, 154. Founder of comparative anatomy, 155. His
domestic life, 155. Some shortcomings, 156. His break with
early friends, 156. Estimate of George Bancroft, 156. Cuvier's
successors: Milne-Edwards, 157; Lacaze-Duthiers, 157; Rich-
ard Owen, 158; Oken, 160; J. Fr. Meckel, 162; Rathke, 163;
J. Miiller, 163; Karl Gegenbaur, 164; E. D. Cope, 165. Com-
parative anatomy a rich subject, 165. It is now becoming exper-
imental, 165.

CHAPTER VIII

Bichat and the Birth of Histology, 166

Bichat one of the foremost men in biological history. He carried the
analysis of animal organization to a deeper level than Cuvier, 166.
Buckle's estimate, 166. Bichat goes to Paris, 167. Attracts at-
tention in Desault's classes, 167. Goes to live with Desault, 168.
His fidelity and phenomenal industry, 168. Personal appear-
ance, 168. Begins to publish researches on tissues at the age of
thirty, 170. His untimely death at thirty-one, 170. Influence
of his vmtings, 170. His more notable successors: Schwann,
171; Koelliker, a striking figure in the development of biology,
171; Max Schultze, 172; Rudolph Virchow, 174; Leydig, 175;
Ramon y Cajal, 176. Modern text-books on histology, 177.

Sav CONTENTS

CHAPTER IX

Thi Rise of Physiology — Harvey. Haller. Johannes Muller, 179

Physiology had a parallel development with anatomy, 179. Physiol-
ogy of the ancients, 179. Galen, 180. Period of Harvey, 180.
His demonstration of circulation of the blood, 180. His method
of experimental investigation, 181. Period of Haller, 181. Phys-
iology developed as an independent science, 183. Haller's per-
sonal characteristics, 181. His idea of vital force, 182. His book
on the Elements of Physiology a valuable work, 183. Discovery
of oxygen by Priestley in 1774, 183. Charles Bell's great discov-
ery on the nervous system, 183. Period of Johannes Muller, 184.
A man of unusual gifts and personal attractiveness, 185. His
personal appearance, 185. His great influence over students, 185.
His especial service was to make physiology broadly comparative,
186. His monumental Handbook of Physiology, 186. Unex-
ampled accuracy in observation, 186. Introduces the principles
of psychology into physiology, 186. Physiology after Muller,
188-195. Ludwig, 188. Du Bois-Reymond, 189. Claude
Bernard, 190. Two directions of growth in physiology — the
chemical and the physical, 192. Influence upon biology, 193.
Other great names in physiology, 194.

CHAPTER X

Von Baer and the Rise of Embryology, 195

Romantic nature of embryology, 195. Its importance, 195. Rudi-
mentary organs and their meaning, 195. The domain of em-
bryology, 196. Five historical periods, 196. The period of
Harvey and Malpighi, 197-205. The embryological work of
these two men insufficiently recognized, 197. Harvey's pioneer
attempt critically to analyze the process of development, 198. His
teaching regarding the nature of development, 199. His treatise
on Generation, 199. The frontispiece of the edition of 165 1, 201,
202. Malpighi's papers on the formation of the chick within the
egg, 202. Quality of his pictures, 202. His belief in preformation,
207. Malpighi's rank as embryologist, 205. The period of
Wolff, 205-214. Rise of the theory of predelineation, 206.
Sources of the idea that the embryo is preformed within the egg,
207. Malpighi's observations quoted, 207. Swammerdam's
view, 208. Leeuwenhoek and the discovery of the sperm, 208.

CONTENTS XV

PAGE

Bonnet's views on emhoUement, 208. Wolff opposes the doctrine
of preformation, 210. His famous Theory of Generation (1759),
210. Sketches from this treatise, 209. His views on the directing
force in development, 211. His highest grade of work, 211.
Opposition of Haller and Bonnet, 211. Restoration of Wolff's
views by Meckel, 212. Personal characteristics of Wolff, 213.
The period of Von Baer, 214-222. The greatest personality in
embryology, 215. His monumental work on the Development of
Animals a choice combination of observation and reflection, 215.
Von Baer's especial service, 217. Establishes the germ -layer
theory, 218. Consequences, 219. His influence on embryology,
220. The period from Von Baer to Balfour, 222-226. The proc-
ess of development brought into a new light by the cell-theory,
222. Rathke, Remak, Koelliker, Huxley, Kowalevsky, 223, 224.
Beginnings of the idea of germinal continuity, 225. Influence of
the doctrine of organic evolution, 226. The period of Balfour,
with an indication of present tendencies, 226-236. The great
influence of Balfour's Comparative Embryology, 226. Person-
ality of Balfour, 228. His tragic fate, 228. Interpretation of the
embryological record, 229. The recapitulation theory, 230.
Oskar Hertwig, 232. Wilhelm His, 232. Recent tendencies;
Experimental embryology, 232; Cell-lineage, 234; Theoretical
discussions, 235.

CHAPTER XI

The Cell-Theory — Schleiden. Schwann. Schultze, . .237

Unifying power of the cell-theory, 237. Vague foreshadowings, 237.
The first pictures of cells from Robert Hooke's Micrographia, 238.
Cells as depicted by Malpighi, Grew, and Leeuwenhoek, 239, 240.
Wolff on cellular structure, 240, 241. Oken, 241. The an-
nouncement of the cell-theory in 1838-39, 242. Schleiden and
Schwann co-founders, 243. Schleiden's work, 243. His ac-
quaintance with Schwann, 243. Schwann's personal appearance,
244. Influenced by Johannes Miiller, 245. The cell-theory his
most important work, 246. Schleiden, his temperament and dis-
position, 247. Schleiden's contribution to the cell-theory, 247.
Errors in his observations and conclusions, 248. Schwann's
treatise, 248. Purpose of his researches, 249. Quotations from
his microscopical researches, 249. Schwann's part in establish-
ing the cell-theory more important than that of Schleiden, 250.
Modification of the cell-theory, 250. Necessity of modifications,
250. The discovery of protoplasm, and its effect on the cell-

XVI CONTENTS

PAGE

theory, 250. The cell-theory becomes harmonized yviih the pro-
toplasm doctrine of Max Schultze, 251. Further modifications of
the cell-theory, 252. Origin of cells in tissues, 252. Structure of
the nucleus, 253. Chromosomes, 254. Centrosome, 256. The
principles of heredity as related to cellular studies, 257. Ver-
worn's definition, 258. Vast importance of the cell-theory in
advancing biology, 258.

CHAPTER XII

Protoplasm the Physical Basis of Life, 259

Great influence of the protoplasm doctrine on biological progress, 259.
Protoplasm, 259. Its properties as discovered by examination of
the amoeba, 260. Microscopic examination of a transparent leaf,
261. Unceasing activity of its protoplasm, 261. The wonderful
energies of protoplasm, 261. Quotation from Huxley, 262. The
discovery of protoplasm and the essential steps in recognizing
the part it plays in Hving beings, 262-275. Dujardin, 262. His
personality, 263. Education, 263. His contributions to science,
264. His discovery of " sarcode V in the simplest animals, in 1835,
266. Purkinje, in 1840, uses the term protoplasma, 267. Von
Mohl, in 1846, brings the designation protoplasm into general
use, 268. Cohn, in 1850, maintains the identity of sarcode and
protoplasm, 270. Work of De Bary and Virchow, 272. Max
Schultze, in 1861, shows that there is a broad likeness between
the protoplasm of animals and plants, and establishes the proto-
plasm doctrine. The university life of Schultze. His love of
music and science. Founds a famous biological periodical, 272-
274. The period from 1840 to i860 an important one for biol-
ogy, 274.

CHAPTER XIII

The Work of Pasteur, Koch, and Others, 276

The bacteria discovered by Leeuwenhoek in 1687, 276. The develop-
ment of the science of bacteriology of great importance to the
human race, 276. Some general topics connected with the study
of bacteria, 277. The spontaneous origin of life, 277-293. Bio-
genesis or abiogenesis, 277. Historical development of the ques-
tion, 277. I. From Aristotle, 325 B.C., to Redi, 1668, 278. The
spontaneous origin of living forms universally believed in, 278.
Illustrations, 278. II. From Redi to Schwann, 278-284. Redi,

CONTENTS XVU

PAGB

in 1668, puts the question to experimental test and overthrows
the belief in the spontaneous origin of forms visible to the un-
aided eye, 279. The problem narrowed to the origin of micro-
scopic animal cula, 281. Needham and Buff on test the ques-
tion by the use of tightly corked vials containing boiled or-
ganic solutions, 281. Microscopic life appears in their infusions,
282. Spallanzani, in 1775, uses hermetically sealed glass flasks
and gets opposite results, 282. The discovery of oxygen raises
another question : Does prolonged heat change its vitalizing prop-
erties? 284. Experiments of Schwann and Schulze, 1836-37,
284. The question of the spontaneous origin of microscopic life
regarded as disproved, 286. III. Pouchet reopens the question
in 1858, maintaining that he finds microscopic life produced in
sterilized and hermetically sealed solutions, 286. The question
put to rest by the brilliant researches of Pasteur and of Tyndall,
288, 289. Description of Tyndall's apparatus and his use of op-
tically pure air, 290. Weismann's theoretical speculations re-
garding the origin of biophors, 292. The germ -theory of disease,
293-304. The idea of contagium vivum revived in 1840, 293.
Work of Bassi, 294. Demonstration, in 1877, of the actual con-
nection between anthrax and splenic fever, 294. Veneration of
Pasteur, 294. His personal quaUties, 296. Fihal devotion, 297.
Steps in his intellectual development, 298. His investigation of
diseases of wine (1868), 299. Of the silk-worm plague (1865-68),
299. His studies on the cause and prevention of disease con-
stitute his chief service to humanity, 299. Establishment of the
Pasteur Institute in Paris, 299. Recent developments, 300.
Robert Koch; his services in discovering many bacteria of dis-
ease, 300. Sir Joseph Lister and antiseptic surgery, 302. Bac-
teria in their relation to agriculture, soil inoculation, etc., 303.
Knowledge of bacteria as related to the growth of general biol-
ogy, 304.

CHAPTER XIV

Heredity and Germinal Continuity — Mendel. Galton. Weis-

MANN, 306

The hereditary substance and the bearers of heredity, 306. The
nature of inheritance, 306, Darwin's theory of pangenesis, 307.
The theory of pangens replaced by that of germinal continuity,
308. Exposition of the theory of germinal continuity, 309. The
law of cell-succession, 309. Omnis cellula e cellula, 310. The
continuity of hereditary substance, 310. Early writers, 311.

xviii CONTENTS

PAGE

Weismann, 312. Germ-cells and body cells, 312. The hered-
itary substance is the germ-plasm, 312. It embodies all the past
history of protoplasm, 312. The more precise investigation of
the material basis of inheritance, 312. The nucleus of '^ells, 312.
The chromosomes, 313, The fertilized ovum, the starting-point
of new organisms, 314. Behavior of the nucleus during division,
314. The mixture of parental qualities in the chromosomes, 314.
Prelocalized areas in the protoplasm of the egg, 315. The in-
heritance of acquired characteristics, 315. The application of
statistical methods and experiments to the study of heredity, 315.
Mendel's important discovery of alternative inheritance, 317.
Francis Galton, 319. Karl Pearson, 321, Experiments on in-
heritance, 321.

CHAPTER XV

The Science of Fossil Remains, . 322

Extinct forms of life, 322. Strange views regarding fossils, 322.
Freaks of nature, 323. Mystical explanations, 323. Large bones
supposed to be those of giants, 3 24. Determination of the nature
of fossils by Steno, 324. Fossil deposits ascribed to the Flood,
325. Mosaic deluge regarded as of universal extent, 326, The
comparison of fossil and living animals of great importance, 327.
Cuvier the founder of vertebrate palaeontology. 327. Lamarck
founds invertebrate palaeontology, 328. Lamarck's conception of
the meaning of fossils more scientific than Cuvier's, 329. The
arrangement of fossils in strata, 330. William Smith, 330. Sum-
mary of the growth of the science of fossil life, 330. Fossil re-
mains as an index to the past history of the earth, 332. Epoch-
making work of Charles Lyell, 332. Effect of the doctrine of
organic evolution on palaeontology, 334. Richard Owen's
studies on fossil animals, 334, Agassiz and the parallelism be-
tween fossil forms of life and stages in the development of
animals, 336. Huxley'sgeological work, 337. Leidy, 339. Cope,
339. Marsh, 340. Carl Zittel's writings and influence, 340.
Henry F. Osborn, 341. Method of collecting fossils, 342, Fossil
remains of man, 342. Discoveries in the Fayiim district of
Africa, 343.

CONTENTS xix

PART II

The Doctrine of Organic Evolution
CHAPTER XVI

PAGE

What Evolution Is: The Evidence upon which it Rests, etc., . 347
Great vagueness regarding the meaning of evolution, 348. Causes for
this, 348. The confusion of Darwinism with organic evolution,
349. The idea that the doctrine is losing ground, 349. Scientific
controversies on evolution relate to the factors, not to the fact, of
evolution, 349. Nature of the question: not metaphysical, not
theological, but historical, 350. The historical method applied
to the study of animal life, 351. The diversity of living forms,
351. Are species fixed in nature? 352, Wide variation among an-
imals, 352. Evolutionary series: The shells of Slavonia and
Steinheim, 353-355. Evolution of the horse, 356. The collec-
tion of fossil horses at the American Museum of Natural History,
New York, 357, The genealogy of the horse traced for more
than two million years, 356. Connecting forms: the archaeop-
teryx and pterodactyls, 360. The embryolo^ical record and its
connection with evolution, 360. Clues to the past history of
animals, 360. Rudimentary organs, 363-365. Hereditary sur-
vivals in the human body, 365. Remains of the scaffolding for
its building, 366. Antiquity of man, 366. Pre-human types, 367.
Virtually three links: the Java man; the Neanderthal skull; the
early neolithic man of Engis, 366-370. Evidences of man's evo-
lution based on palaeontology, embryology, and archaeology, 372.
Mental evolution, 372. Sweep of the doctrine of organic evolu-
tion, 372-373.

CHAPTER XVII

Theories of Evolution — Lamarck. Darwin, . . . .374

The attempt to indicate the active factors of evolution is the source of
the different theories, 374. The theories of Lamarck, Darwin,
and Weismann have attracted the widest attention, 375. La-
marck, the man, 374-380. His education, 376. Leaves priestly
studies for the army, 376. Great bravery, 377. Physical injury
makes it necessary for him to give up military life, 377. Por-
trait, 379. Important work in botany, 377. Pathetic poverty

XX CONTENTS

PAGE

and neglect, 378. Changes from botany to zoology at the age of
fifty years, 378. Profound influence of this change in shaping
his ideas, 380. His theory of evolution, 380-386. First public
announcement in 1800, 381. His Philosophie Zoologique pub-
lished in 1809, 381. His two laws of evolution, 382. The first
law embodies the principle of use and disuse of organs, the second
that of heredity, 380. A simple exposition of his theory, 383.
His employment of the word hesoin, 383. Lamarck's view of
heredity, 383. His belief in the inheritance of acquired char-
acters, 383. His attempt to account for variation, 383. Time
and favorable conditions the two principal means employed by
nature, 384. Salient points in Lamarck's theory, 384. His
definition of species, 385. Neo-Lamarckism, 386. Darwin. His
theory rests on three sets of facts. The central feature of his
theory is natural selection. Variation, 386. Inheritance, 388.
Those variations v/ill be inherited that are of advantage to the
race, 389. Illustrations of the meaning of natural selection, 389-
S95. The struggle for existence and its consequences, 390. Vari-
ous aspects of natural selection, 390. It does not always operate
toward increasing the efficiency of an organ — short-winged
beetles, 391. Color of animals, 392. Mimicry, 393. Sexual
selection, 394. Inadequacy of natural selection, 395. Darwin
the first to call attention to the inadequacy of this principle, 395.
Confusion between the theories of Lamarck and Darwin, 396.
Illustrations, 397. The Origin of Species published in 1859,
397. Other writings of Darwin, 397.

CHAPTER XVIII

Theories Continued — Weismann. De Vries, .... 398
Weismann's views have passed through various stages of remodeling,
398. The Evolution Theory published in 1904 is the best ex-
position of his views, 398. His theory the field for much contro-
versy. Primarily a theory of heredity, 399. Weismann's theory
summarized, 399. Continuity of the germ-plasm the central idea
in Weismann's theory, 400. Complexity of the germ-plasm. Il-
lustrations, 401. The origin of variations, 402. The union of
two complex germ-plasms gives rise to variations, 402. His ex-
tension of the principle of natural selection — germinal selection,
403. The inheritance of acquired characters, 404. Weismann's
analysis of the subject the best, 403. Illustrations, 405. The
question still open to experimental observation, 405. Weis-

CONTENTS xxj

PAGE

mann's personality, 406. Quotation from his autobiography, 408.
The mutation theory of De Vries, 408. An important contribu-
tion. His appUcation of experiments commendable, 40Q. The
mutation theory not a substitute for that of natural selection, 410.
Tendency toward a reconciliation of apparently conflicting views,
410. Summary of the salient features of the theories of Lamarck,
of Darwin, of Weismann, and De Vries, 411. Causes for bewil-
derment in the popular mind regarding the different forms of the
evolution theory, 414.

CHAPTER XIX

The Rise of Evolutionary Thought, 415

Opinion before Lamarck, 415. Views of certain Fathers of the
Church, 416. St. Augustine, 416, St. Thomas Aquinas, 417.
The rise of the doctrine of special creation, 418. Suarez, 418.
Effect of John Milton's writings, 417. Forerunners of Lamarck:
Buffon, Erasmus Darwin, Goethe, 419. Statement of Buffon's
views on evolution, 420. Erasmus Darwin the greatest of La-
marck's predecessors, 421. His writings, 422. Paley's Natural
Theology directed against them, 422, Goethe's connection with
evolutionary thought, 422. Causes for the neglect of Lamarck's
theoretical writings, 422. The temporary disappearance of the
doctrine of organic evolution. 423. Cuvier's opposition, 423.
The debate between Cuvier and St. Hilaire, 423. Its effect, 425.
Influence of Lyell's Principles of Geology, 426. Herbert Spen-
cer's analysis in 1852, 427. Darwin and Wallace, 428. Circum-
stances under which their work was laid before the Linnaean
Society of London, 428. The letter of transmission signed by
Lyell and Hooker, 428-430. The personality of Darwin, 430.
Appearance, 431. His charm of manner, 431. Affectionate
consideration at home, 432. Unexampled industry and con-
scientiousness in the face of ill health, 432, 434. His early
life and education, ^^:^. Voyage of the Beagle, 433. The re-
sults of his five years' voyage, 434. Life at Down, 434.
Parallelism in the thought of Darwin and Wallace, 435. Dar-
win's account of how he arrived at the conception of natural
selection, 435. Wallace's narrative, 435. The Darwin-Wallace
theory launched in 1858, 437. Darwin's book on The Origin of
Species regarded by him as merely an outline, 437. The spread
of the doctrine of organic evolution, 437. Huxley one of its great
popular exponents, 438. Haeckel, 439. After Darwin, the prob-
lem was to explain phenomena, 441.

xxii CONTENTS

PAGE

CHAPTER XX

Retrospect and Prospect. Present Tendencies in Biology, . 442
Biological thought shows continuity of development, 442. Character
of the progress — a crusade against superstition, 442. The first
triumph of the scientific method was the overthrow of authority,
443. The three stages of progress — descriptive, comparative, ex-
perimental, 443. The notable books of biology and their authors,
443-445. Recent tendencies in biology: higher standards, 445;
improvement in the tools of science, 446; advance in methods,
447; experimental work, 447; the growing interest in the study
of processes, 448; experiments applied to heredity and evolution,
to fertilization of the egg, and to animal behavior, 448, 449.
Some tendencies in anatomical studies, 450. Cell-lineage, 450,
New work on the nervous system, 451, The application of
biological facts to the benefit of mankind, 451. Technical biol-
ogy, 451. Soil inoculation, 452. Relation of insects to the trans-
mission of diseases, 452. The food of fishes, 452. The establish-
ment and maintenance of biological laboratories, 452. The sta-
tion at Naples, 452. Other stations, 454. The establishment and
maintenance of technical periodicals, 454. Explorations of fossil
records, 455. The reconstructive influence of biological prog-
ress, 456.

READING LIST, 457

I. General References, 451-459. II. Special References, 459-468.

Index, , . 471

ILLUSTRATIONS

FIG. PAGH

1. Aristotle, 384-322 b.c, 14

2. Pliny, 23-79 a.d., 16

3. Galen, 131-200, 25

4. VesalIus, 1514-1565, .* 29

5. Anatomical Sketch from Vesalius' Fahrica (1543), . • 31

6. The Skeleton from Vesalius' Fahrica, 2)2>

7. Initial Letters from the Fahrica, 34

8. Fallopius, 1523-1563, 37

9. Fabricius, Harvey's Teacher, 1537-1619, . . . - '^Z

10. William Harvey, 1578-1657, 44

11. Scheme of the Portal Circulation according to Vesalius

(i543)» 49

12. Hooke's Microscope (1665), 55

13. Malpighi, 1 628-1 694, 59

14. From Malpighi's Anatomy oj the Silkworm (1669), . . • 65

15. Swammerdam, 1 63 7-1 680, o . 69

16. From Swammerdam's Bihlia Natur-^, . . . . -74

1 7. Anatomy of an Insect Dissected and Drawn by Swammerdam, 76

18. Leeuwenhoek, 1632-1723, =79

19. Leeuwenhoek's Microscope, . 82

20a. Leeuwenhoek's Mechanism for Examining the Circulation

OF the Blood, 8^

20b. The Capillary Circulation, after Leeuwenhoek, . . 84

21. Plant Cells from Leeuwenhoek's Arcana Natures, . . 86

22. Lyonet, 1 707-1 789, 90

23. Larva of the Willow Moth, from Lyonet's Monograph

(1750), 92

24. Muscles of the Larva of the Willow Moth, from Lyonet's

Monograph, 93

25. Central Nervous System and Nerves of the Same Animal, 93

26. Dissection of the Head of the Larva of the Willow Moth, 94

27. The Brain AND Head Nerves OF THE Same Animal, . . .95

28. roesel von rosenhof, 1705-1759, ..... 97

29. Reaumur, 1683-175 7, . .98

zxiii

XXIV ILLUSTRATIONS

FIG. PAGE

30. Nervous System of the Cockchafer, from Straus-Durck-

heim's Monograph (1828), . . . . . • .101

31. Ehrenberg, 1795-1876, 108

32. Gesner, 1516-1565, 114

^^. John Ray, 1628-1705, 116

34. LiNN^us (1707-17 78) AT Sixty, 124

35. Karl Th. von Siebold, 13S

36. Rudolph Leuckart, 136

37. Severinus, 1580-1656, 142

38. Camper, 1772-1789, i44

39. John Hunter, 17 28-1 793, i45

40. ViCQ d'Azyr, 1 748-1 794, 147

41. Cuvier (1769-1829) as a Young Man, 152

42. Cuvier at the Zenith of His Power, 153

43. H. Milne-Edwards, 1800-1885, . . ... . -157

44. Lacaze-Duthiers, 1821-1901, ....... 159

45. Lorenzo Oken, 1779-1851, 160

46. Richard Owen, 1804-1892, . . . ... . . 161

47. J. Fr. Meckel, 1781-1833, 162

48. Karl Gegenbaur, 1826-1903, 164

49. BicHAT, 1771-1801, 169

50. Von KoellikeRj^'TSi 7-1905, 173

51. Rudolph Virchow, 1821-1903, 174

52. Franz Leydig, 1821-1908 175

53. S. Ramon y Cajal, 176

54. Albrecht Haller, 1708-1777, 182

55. Charles Bell, i 774-1842, 184

56. Johannes Muller, 1801-1858, 187

57. Ludwig, 1816-1895, 188

58. Du Bois-Reymond, 1818-1896, 189

59. Claude Bernard, 1813-1878, . .191

60. Frontispiece of Harvey's Generatione Animalium (1651), . 201

61. Selected Sketches from Malpighi's Works, . . . 203

62. Marcello Malpighi, 1 628-1 694, 204

63. Plate from Wolff's Theoria Generationis (1759), . . . 209

64. Charles Bonnet, i 720-1793, 212

65. Karl Ernst von Baer, i 792-1876, 216

66. Von Baer at about Seventy Years of Age, . . . .217

67. Sketches from Von Baer's Embryological Treatise (1828), 221

68. A. Kowalevsky, 1840-1901, 225

69. Francis M. Balfour, 1851-1882, 227

70. OSKAR HeRTWIG in 189O, 23 1

71. WiLHELM His, 1831-1904, 233

ILLUSTRATIONS

XXV

FIG.

72.

73-

74-
75-
76.

77-
78.

79-
80.
81.

82.

83-
84.

85-
86.
87.
88.
89.
90.
91.

92.

93.
94.

94a

95-
96.

97.
98.

99.
100.

lOI.

102.
103.
104.

The Earliest Known Picture or Cells, from Hooke's Micro-
graphia (1665),

Sketch from Malpighi's Treatise on the Anatomy of Plants
(1670),

Theodor Schwann, 1810-1882,

M. ScHLEiDEN, 1 804-1 88 1,

The Egg and Early Stages in Its Development (after Ge-
genbaur),

An Early Stage in the Development of the Egg of a Rock
Limpet (after Conklin),

Highly Magnified Tissue-Cells from the Skin of a Sala-
mander (after Wilson),

Diagram of the Chief Steps in Cell-Division (after Parker),

Diagram of a Cell (modified after Wilson),

{A) Rotation OF Protoplasm IN Cells OF NiTELLA. {B) High-
ly Magnified Cells of a Tradescantia Plant, Showing
Circulation of Protoplasm (after Sedgwick and Wilson),

Felix Dujardin, i 801-1860,

Purkinje, 1 787-1869,

Carl Nageli, 181 7-189 i,

Hugo von Mohl, 1805-1872,

Ferdinand Cohn, i 828-1 898,

Heinrich Anton De Bary, 1831-1888,

Max Schultze, 1825-1874,

Francesco Redi, 1626-169 7,

Lazzaro Spallanzani, 1 729-1799,

Apparatus of Tyndall for Experimenting on Spontaneous
Generation, . , 290

238

239
245
246

253

254

255
256

257

261
265
267
268
269
271
272

280

283

Louis Pasteur (1822-1895) and His Granddaughter,
Robert Koch, 1843-1910,
Slr Joseph Lister, 1827-1912,
Fritz Schaudinn, 1871-1906,
Gregor Mendel, 1822-1884,
Francis Galton, 1822-1911,
Charles Lyell, i 797-1875, .
Professor Owen and the Extinct Fossil B

land, ....

Louis Agassiz, 1807-1873,
E. D. Cope, 1840-1897,
O. C. Marsh, 1831-1899,
Karl von Zittel, i 839-1 904,
Transmutations of Paludina (after Neumayer),
Planorbis Shells from Steinheim (after Hyatt)

rd of New Zea

295
301
302

304
316

319

335
336
338
339
341
354
355

XXVI

ILLUSTRATIONS

FIG. PAGE

105. Bones of the Foreleg of a Horse, 358

106. Bones of Fossil Ancestors of the Horse, . . . 359

107. Representation of the Ancestor of the Horse Drawn by

Charles R. Knight under the Direction of Professor
OsBORN. Permission of the American Museum of Natural
History,

108. Fossil Remains of a Primitive Bird (Arch^opteryx),

109. Gill-clefts of a Shark Compared with those of the Em

bryonic Chick and Rabbit, .....
no. Jaws of an Embryonic Whale, showing Rudimentary Teeth, 364

111. Profile Reconstructions of the Skulls of Living and of

Fossil Men, 371

112. Lamarck, i 744-1829,

113. Charles Darwin, 1809-1882,

114. August Weismann, i 834-1914,

115. Hugo de Vries, .

116. Buffon, 1 707-1 788,

117. Erasmus Darwin, i 731-1802,
108. Geoffroy Saint Hilaire, i 772-1844,

119. Charles Darwin, 1809-1882,

120. Alfred Russel Wallace, 1823-1913,

121. Thomas Henry Huxley, 1825-1895,

122. Ernst Haeckel, born 1834,

123. The Biological Station at Naples,

361
362

363

379
387
406
409
420
421
424
431
436
438
440

453

PART I

THE SOURCES OF BIOLOGICAL

IDEAS EXCEPT THOSE OF

ORGANIC EVOLUTION

CHAPTER I

AN OUTLINE OF THE RISE OF BIOLOGY AND OF
THE EPOCHS IN ITS HISTORY

"Truth is the Daughter of Time."

The nineteenth century will be for all time memorable
for the great extension of the knowledge of organic nature.
It was then that the results of the earlier efforts of mankind
to interpret the mysteries of nature began to be fruitful;
observers of organic nature began to see more deeply into
the province of life, and, above all, began to see how to direct
their future studies. It was in that century that the use of
the microscope made known the similarity in cellular con-
struction of all organized beings; that the substance, proto-
plasm, began to be recognized as the physical basis of life
and the seat of all vital activities; then, most contagious
diseases were traced to microscopic organisms, and as a con-
sequence, medicine and surgery were reformed; then the
belief in the spontaneous origin of life under present condi-
tions was given up; and it was in that century that the
doctrine of organic evolution gained general acceptance.
These and other advances less generally known created an
atmosphere in which biology — the great life-science — grew
rapidly.

In the same period also the remains of ancient life, long
since extinct, and for countless ages embedded in the rocks,
were brought to light, and their investigation assisted mate-
rially in understanding the living forms and in tracing their
genealogy.

3

4 BIOLOGY AND ITS MAKERS

As a result of these advances, animal organization began
to have a different meaning to the more discerning naturalists,
those whose discoveries began to influence the trend of
thought, and finally, the idea which had been so often pre-
viously expressed became a settled conviction, that all the
higher forms of life are derived from simpler ones by a gradual
process of modification.

Besides great progress in biology, the nineteenth century
was remarkable for similar advances in physics and chem-
istry. Although these subjects purport to deal with inorganic
or lifeless nature, they touch biology in an intimate way.
The vital processes which take place in all animals and plants
have been shown to be physico-chemical, and, as a conse-
quence, one must go to both physics and chemistry in order
to understand them. The study of organic chemistry in late
years has greatly influenced biology; not only have living
products been analyzed, but some of them have already been
constructed in the chemical laboratory. The formation of
living matter through chemical means is still far from the
thought of most chemists, but very complex organic com-
pounds, which were formerly known only as the result of
the action of life, have been produced, and the possibilities
of further advances in that direction are very alluring. It
thus appears that the discoveries in various fields have
worked together for a better comprehension of nature.

The Domain of Biology. — The history of the transforma-
tion of opinion in reference to living organisms is an inter-
esting part of the story of intellectual development. The
central subject that embraces it all is biology. This is one
of the fundamental sciences, since it embraces all questions
relating to life in its different phases and manifestations.
Everything pertaining to the structure, the development, and
the evolution of living organisms, as well as to their physiol-
ogy, belongs to biology. It is now of commanding impor-

OUTLINE OF BIOLOGICAL PROGRESS 5

tance in the world of science, and it is coming more and more
to be recognized that it occupies a field of compelling in-
terest not only for medical men and scholars, but for all
intelligent people. The discoveries and conquests of biology
have wrought such a revolution in thought that they should
be known to all persons of liberal culture. In addition to
making acquaintance with the discoveries, one ought to learn
something about the history of biology; for it is essential
to know how it took its rise, in order to understand its
present position and the nature of its influence upon expand-
ing ideas regarding the world in which we live.

In its modern sense, biology did not arise until about
i860, when the nature of protoplasm was first clearly pointed
out by Max Schultze, but the currents that united to form it
had long been flowing, and we can never understand the
subject without going back to its iatric condition, when what
is now biology was in the germ and united with medicine.
Its separation from medicine, and its rise as an independent
subject, was owing to the steady growth of that zest for ex-
ploration into unknown fields which began with the new
birth of science in the sixteenth century, and has continued
in fuller measure to the present. It was the outcome of
applying observation and experiment to the winning of new
truths.

Difficulties. — But biology is so comprehensive a field,
and involves so many details, that it is fair to inquire: can
its progress be made clear to the reader who is unacquainted
with it as a laboratory study ? The matter will be simplified
by two general observations — first, that the growth of biology
is owing to concurrent progress in three fields of research,
concerned, respectively, with the structure or architecture of
living beings, their development, and their physiology. We
recognize also a parallel advance in the systematic classifica-
tion of animals and plants, and we note, furthermore, that

O BIOLOGY AND ITS MAKERS

the idea of evolution permeates the whole. It will be neces-
sary to consider the advances in these fields separately, and
to indicate the union of the results into the main channel of
progress. Secondly, in attempting to trace the growth of ideas
in this department of learning one sees that there has been
a continuity of development. The growth of these notions
has not been that of a chaotic assemblage of ideas, but a
well-connected story in which the new is built upon the old
in orderly succession. The old ideas have not been com-
pletely superseded by the new, but they have been molded
into new forms to keep pace with the advance of investigation.
In its early phases, the growth of biology was slow^ and dis-
cursive, but from the time of Linnaeus to Darwin, although
the details were greatly multiplied, there has been a relatively
simple and orderly progress.

Facts and Ideas. — There are many books about biology,
with directions for laboratory observation and experiment,
and also many of the leading facts of the science have been
given to the public, but an account of the growth of the ideas,
which are interpretations of the facts, has been rarely at-
tempted. From the books referred to, it is almost impossible
to get an idea of biology as a unit; this even the students in
our universities acquire only through a coherent presentation
of the subject in the classroom, on the basis of their work in
the laboratory. The critical training in the laboratory is
most important, but, after all, it is only a part, although an
essential part, of a knowledge of biology. In general, too
little attention is paid to interpretations and the drill is con-
fined to a few facts. Now, the facts are related to the ideas
of the science as statistics to history — meaningless without
interpretation. In the rise of biology the facts have accu-
mulated constantly, through observation and experiment, but
the general truths have emerged slowly and periodically,
whenever there has been granted to some mind an insight

OUTLINE OF BIOLOGICAL PROGRESS 7

into the meaning of the facts. The detached facts are some-
times tedious, the interpretations always interesting.

The growth of the knowledge of organic nature is a long
story, full of human interest. Nature has been always the
same, but the capacity of man as its interpreter has varied.
He has had to pass through other forms of intellectual activ-
ity, and gradually to conquer other phases of natural phe-
nomena, before entering upon that most difficult task of
investigating the manifestations of life. It will be readily
understood, therefore, that biology was delayed in its devel-
opment until after considerable progress had been made in
other sciences.

It is an old saying that "Truth is the daughter of Time,"
and no better illustration of it can be given than the long
upward struggle to establish even the elemental truths of
nature. It took centuries to arrive at the conception of the
uniformity of nature, and to reach any of those generaliza-
tions which are vaguely spoken of as the laws of nature.

The Men of Science. — In the progress of science there is
an army of observers and experimenters each contributing
his share, but the rank and file supply mainly isolated facts,
while the ideas take birth in the minds of a few gifted leaders,
either endowed with unusual insight, or so favored by cir-
cumstances that they reach general conclusions of importance.
These advance-guards of intellectual conquest we designate
as founders. What were they like in appearance? Under
what conditions did they work, and what was their chief aim?
These are interesting questions which will receive attention
as our narrative proceeds.

A study of the lives of the founders shows that the scien-
tific mood is pre-eminently one of sincerity. The men who
have added to the growth of science were animated by an
unselfish devotion to truth, and their lasting influence has
been in large measure a reflection of their individual char-

8 BIOLOGY AND ITS MAKERS

acters. Only those have produced permanent residts who
have interrogated nature in the spirit of devotion to truth
and waited patiently for her replies. The work founded on
selfish motives and vanity has sooner or later fallen by the
wayside. We can recognize now that the work of scientific
investigation, subjected to so much hostile criticism as it
appeared from time to time, was undertaken in a reverent
spirit, and was not iconoclastic, but remodelling in its in-
fluence. Some of the glories of our race are exhibited in
the lives of the pioneers in scientific progress, in their struggles
to establish some great truth and to maintain intellectual
integrity.

The names of some of the men of biology, such as Harvey,
Linnaeus, Cuvier, Darwin, Huxley, and Pasteur, are widely
known because their work came before the people, but others
equally deserving of fame on account of their contributions
to scientific progress will require an introduction to most of
our readers.

In recounting the story of the rise of biology, we shall
have occasion to make the acquaintance of this goodly com-
pany. Before beginning the narrative in detail, however,
we shall look summarily at some general features of scientific
progress and at the epochs of biology.

The Conditions under which Science Developed

In a brief sketch of biology there is relatively little in the
ancient world that requires notice except the work of Aris-
totle and Galen; but with the advent of Vesalius, in 1543,
our interest begins to freshen, and, thereafter, through lean
times and fat times there is always something to command
our attention.

The early conditions must be dealt with in order to appre-
ciate what followed. We are to recollect that in the ancient

OUTLINE OF BIOLOGICAL PROGRESS 9

world there was no science of biology as such; nevertheless,
the germ of it was contained in the medicine and the natural
history of those times.

There is one matter upon which we should be clear: in
the time of Aristotle nature was studied by observation and
experiment. This is the foundation of all scientific ad-
vancement. Had conditions remained unchanged, there is
reason to believe that science would have developed steadily
on the basis of the Greek foundation, but circumstances, to
be spoken of later, arose which led not only to the complete
arrest of inquiry, but also, the mind of man being turned
away from nature, to the decay of science.

Aristotle the Founder of Natural History. — The Greeks
represented the fullest measure of culture in the ancient
world, and, naturally, we find among them the best-developed
science. All the knowledge of natural phenomena centered
in Aristotle (384-322 B.C.), and for twenty centuries he
represented the highest level which that kind of knowledge
had attained.

It is uncertain how long it took the ancient observers to
lift science to the level which it had at the beginning of
Aristotle's period, but it is obvious that he must have had
a long line of predecessors, who had accumulated facts of
observ^ation and had molded them into a system before he
perfected and developed that system. We are reminded
that all things are relative when we find Aristotle referring
to the ancients; and well he might, for we have indubitable
evidence that much of the scientific work of antiquity has
been lost. One of the most striking discoveries pointing
in that direction is the now famous papyrus which was found
by Georg Ebers in Egypt about i860. The recent trans-
lation of this ancient document shows that it was a treatise
on medicine, dating from the fifteenth century B.C. At this
time the science of medicine had attained an astonishingly

lO BIOLOGY AND ITS MAKERS

high grade of development among that people. And since
it is safe to assume that the formulation of a system of med-
icine in the early days of mankind required centuries of
observation and practice, it becomes apparent that the
manuscript in question was no vague, first attempt at reduc-
ing medicine to a system. It is built upon much scientific
knov^ledge, and must have been preceded by writings both
on medicine and on its allied sciences.

It is not necessary that we should attempt to picture the
crude beginnings of the observation of animated nature and
the dawning of ideas relative to animals and plants; it is
suitable to our purpose to commence with Aristotle, and to
designate him, in a relative sense, as the founder of natural
history.

That he was altogether dissatisfied with the state of
knowledge in his time and that he had high ideals of the
dignity of science is evidenced in his writings. Although he
refers to the views of the ancients, he regarded himself in
a sense as a pioneer. "I found no basis prepared," he says,
" no models to copy. . . . Mine is the first step, and there-
fore a small one, though worked out with much thought
and hard labor. It must be looked at as a first step and
judged with indulgence." (From Osbom's From the Greeks
to Darwin.)

There is general agreement that Aristotle was a man of
vast intellect and that he was one of the greatest philosophers
of the ancient world. He has had his detractors as w^ell as
his partisan adherents. Perhaps the just estimate of his
attainments and his position in the history of science is
between the enthusiastic appreciation of Cuvier and the
critical estimate of Lewes.

This great man was born in Stagira in the year 384 B.C.,
and lived until 322 B.C. He is to be remembered as the
most distinguished pupil of Plato, and as the instructor of

OUTLINE OF BIOLOGICAL PROGRESS 1 1

Alexander the Great. Like other scholars of his time, he
covered a wide range of subjects; we have mention, indeed,
of about three hundred works of his composition, many of
which are lost. He wrote on philosophy, metaphysics, psy-
chology, politics, rhetoric, etc., but it was in the domain of
natural history that he attained absolute pre-eminence.

His Position in the Development of Science. — It is mani-
festly unjust to measure Aristotle by present standards ; we
must keep always in mind that he was a pioneer, and that
he lived in an early day of science, when errors and crudities
were to be expected. His greatest claim to eminence in the
history of science is that he conceived the things of importance
and that he adopted the right method in trying to advance
the knowledge of the natural universe. In his program
of studies he says : " First we must understand the phenomena
of animals; then assign their causes; and, finally, speak of
their generation." His position in natural history is fre-
quently misunderstood. One of the most recent writers on
the history of science, Henry Smith Williams, pictures him
entirely as a great classifier, and as the founder of systematic
zoology. While it is true that he was the foimder of sys-
tematic zoology, as such he did not do his greatest service
to natural history, nor does the disposition to classify repre-
sent his dominant activity. In all his work classification is
made incidental and subservient to more important considera-
tions. His observations upon structure and development,
and his anticipation of the idea of organic evolution, are the
ones upon which his great fame rests. He is not to be remem-
bered as a man of the type of Linnaeus; rather is he the fore-
runner of those men who looked deeper than Linnaeus into
the structure and development of animal life — the mor-
j)hologists.

Particular mention of his classification of animals will
be found in the chapter on Linnaeus, while in what follows

12 BIOLOGY AND ITS MAKERS

in this chapter attention will be confined to his observation
of their structure and development and to the general in-
fluence of his work.

His great strength was in a philosophical treatment of
the structure and development of animals. Professor Osborn
in his interesting book, From the Greeks to Darwin^ shows
that Aristotle had thought out the essential features of
evolution as a process in nature. He believed in a complete
gradation from the lowest organisms to the highest, and that
man is the highest point of one long and continuous ascent.

His Extensive Knowledge of Animals. — He made exten-
sive studies of life histories. He knew that drone bees
develop without previous fertilization of the eggs (by par-
thenogenesis) ; that in the squid the yolk sac of the embryo
is carried in front of the mouth; that some sharks develop
within the egg-tube of the mother, and in some species have
a rudimentary blood -connection resembling the placenta of
mammals. He had followed day by day the changes in the
chick within the hen's o^gg, and observed the development of
many other animals. In embryology also, he anticipated
Harvey in appreciating the true nature of development as
a process of gradual building, and not as the mere expansion
of a previously formed germ. This doctrine, v/hich is known
under the name of epigenesis, was, as we shall see later,
hotly contested in the eighteenth century, and has a modified
application at the present time.

In reference to the structure of animals he had described
the tissues, and in a rude way analyzed the organs into their
component parts. It is known, furthermore, that he prepared
plates of anatomical figures, but, unfortunately, these have
been lost.

In estimating the contributions of ancient writers to
science, it must be remembered that we have but fragments
of their works to examine. It is, moreover, doubtful whether

OUTLINE OF BIOLOGICAL PROGRESS 13

the scientific writings ascribed to Aristotle were all from his
hand. The work is so uneven that Huxley has suggested
that, since the ancient philosophers taught viva voce, what
we have of his zoological writings may possibly be the notes
of some of his students. While this is not known to be the
case, that hypothesis enables us to understand the intimate
mixture of profound observation with trivial matter and
obvious errors that occur in the writings ascribed to him.

Hertwig says: "It is a matter for great regret that there
have been preserved only parts of his three most important
zoological works, ^ Historia animalium,^ ^ Dc partibus,^ and
' De gen era Hone, ^ works in which zoology is founded as a
universal science, since anatomy and embryology, physiology
and classification, find equal consideration."

Some Errors. — Dissections were little p)ractised in his
day, and it must be admitted that his observations embrace
many errors. He supposed the brain to be bloodless, the
arteries to carry air, etc., but he has been cleared by Huxley
of the mistake so often attributed to him of supposing the
heart of mammals to have only three chambers. It is alto-
gether probable that he is credited with a larger number of
errors than is justified by the facts.

He must have had unusual gifts in the exposition of these
technical subjects; indeed, he made his researches appear
so important to his royal patron, Alexander, that he was
aided in the preparation of his great Natural History by a
grant of 800 talents (equivalent to $200,000) and by nu-
merous assistants and collectors. Thus in ancient times was
anticipated the question that is being agitated to-day — that
of the support and the endowment of research.

Personal Appearance. — Some idea of his looks may be
gained from Fig. i. This is a copy of a bas-relief found in
the collection of Fulvius Ursinus (d. 1600), and was originally
published by J. Fabcr. Its authenticity as a portrait is

14

BIOLOGY AND ITS MAKERS

attested (1811) by Visconti, who says that it has a perfect
resemblance to the head of a small bust upon the base of
which the name of Aristotle is engraved. Portrait busts and
statues of Aristotle were common in ancient times. The
picture of him most familiar to general readers is the copy
of the head and shoulders of an ancient statue representing
him with a draping over the left shoulder. This is an

Fig. I. — Aristotle, 384-322 B.C.

attractive portrait, showing a face of strong intellectuality.
Its authenticity, however, is not as well established as that
of the picture shown here. Other pictures, believed to be
those of Aristotle, represent him later in life with receding
hair, and one exists in which his baldness is very extensive.
He was described as short in stature, with spindling legs and
small, penetrating eyes, and to have been, in his younger
days, vain and showy in his dress.

OUTLINE OF BIOLOGICAL PROGRESS ^5

He was early left an orphan with a considerable fortune;
and there are stories of early excesses after coming into his
property. These charges, however, lack trustworthy support,
and are usually regarded as due mainly to that under-
mining gossip which follows one holding prominent place
and enviable recognition. His habits seem to have been
those of a diligent student Vv^ith a zest in his work; he was an
omnivorous reader, and Plato called him the mind of his
school. His large private library and his manner of liv-
ing bespeak the conserving of his property, rather than its
waste in selfish indulgences.

His Influence. — The influence of Aristotle was in the
right direction. He made a direct appeal to nature for his
facts, and founded his Natural History only on observation
of the structure, physiology, and development of animals.
Unfortunately, the same cannot be said of his successors.

Galen, who is mentioned above in connection with Aris-
totle, was a medical writer and the greatest anatomist of
antiquity. On account of the relation of his work to the
growth of anatomy, however, the consideration of it is re-
served for the chapter on Vesalius.

Soon after the period of Aristotle the center of scientific
investigation was transferred to Alexandria, where Ptolemy
had erected a great museum and founded a large public
library. Here mathematics and geography flourished, but
natural history was little cultivated.

In order to find the next famous naturalist of antiquity,
it is necessary to look to Rome. Rome, although great in
political power, never became a true culture center, char-
acterized by originality. All that remains of their thought
shows us that the Roman people were not creative. In the
capital of the empire, the center of its life, there arose no
great scientific investigator.

Pliny. — The situation is represented by Pliny the Elder

1(5

BIOLOGY AND ITS MAKERS

(23-79 A.D.), the Roman general and litterateur (Fig. 2).
His works on natural history, filling thirty-seven volumes,
have been preserved with greater completeness than those of
other ancient writers. Their overwhelming bulk seems to
have produced an impression upon those who, in the nine-
teenth century, heralded him as the greatest naturalist of

Fig. 2. — Pliny, 23-79 a.d.

antiquity. But an examination of his writings shows that
he did nothing to deepen or broaden the knowledge of nature,
and his Natural History marks a distinct retrograde movement.
He was, at best, merely a compiler — " sl collector of anec-
dotes " — who, forsaking observation, indiscriminately mixed
fable, fact, and fancy taken from the writings of others.
He emphasized the feature of classification which Aristotle
had held in proper subordination, and he replaced the clas-

OUTLINE OF BIOLOGICAL PROGRESS I?

sification of Aristotle, founded on plan of organization, by a
highly artificial one, founded on the incidental circumstance
6f the abodes of animals — either in air, water, or on the earth.

The Arrest of Inquiry and its Effects. — Thus, natural
history, transferred from a Greek to a Roman center, was
already on the decline in the time of Pliny; but it was des-
tined to sink still lower. It is an old, oft-repeated story how,
with the overthrow of ancient civilization, the torch of learn-
ing was nearly extinguished. Not only was there a complete
political revolution ; there was also a complete change in the
mental interests of mankind. The situation is so complex
that it is difficult to state it with clearness. So far as science
is concerned, its extinction was due to a turning away from
the external world, and a complete arrest of inquiry into the
phenomena of nature. This was an important part of that
somber change which came over all mental life.

One of the causes that played a considerable part in the
cessation of scientific investigation was the rise of the Chris-
tian church and the dominance of the priesthood in all intellec-
tual as well as in spiritual life. The world shunning spirit,
so scrupulously cultivated by the early Christians, prompted
a spirit which was hostile to observation. The behest to
shun the world was acted upon too literally. The eyes were
closed to nature and the mind was directed tov/ard spiritual
matters, which truly seemed of higher importance. Pres-
ently, the observation of nature came to be looked upon as
proceeding from a prying and impious curiosity.

Books were now scarcer than during the classical period ;
the schools of philosophy were reduced, and the dissemina-
tion of learning ceased. The priests who had access to the
books assumed direction of intellectual life. But they were
largely employed with the analysis of the supernatural,
without the wholesome check of observation and experiment ;
mystical explanations were invented for natural phenomena,

.l8 BIOLOGY AND ITS MAKERS

while metaphysical speculation became the dominant form
of mental activity.

Authority Declared the Source of Knowledge. — In this
atmosphere controversies over trivial points were engendered,
and the ancient writings were quoted as sustaining one side
or the other. All this led to the referring of questions as to
their truth or error to authority as the source of knowledge,
and resulted in a complete eclipse of reason. Amusing illus-
trations of the situation are abundant; as when, in the
Middle Ages, the question of the number of teeth in the horse
was debated with great heat in many contentious writings.
Apparently none of the contestants thought of the simple
expedient of counting them, but tried only to sustain their
position by reference to authority. Again, one who noticed
spots on the sun became convinced of the error of his eyes
because Aristotle had somewhere written "The face of the
sun is immaculate."

This was a barren period not only for science, but also
for ecclesiastical advance. Notwithstanding the fact that
for more than a thousand years the only new works were
written by professional theologians, there was no substantial
advance in their field, and we cannot escape the reflection
that the reciprocal action of free inquiry is essential to the
growth of theology as of other departments of learning.

In the period from the downfall of Rome to the revival
of learning, one eminent theologian, St. Augustine, stands
in relief for the openness of his mind to new truth and for
his expressions upon the relation of revelation in the Scrip-
tures to the observation of nature. His position will be more
clearly indicated in the chapter dealing with the rise of
evolutionary thought.

Perhaps it has been the disposition of historians to paint
the Middle Ages in too dark colors in order to provide a
background on which fitly to portray the subsequent awak-

OUTLINE OF BIOLOGICAL PROGRESS 19

ening. It was a remolding period through which it was
necessary to pass after the overthrow of ancient civilization
and the mixture of the less advanced people of the North with
those of the South. The opportunities for advance were
greatly circumscribed ; the scarcity of books and the lack of
facilities for travel prevented any general dissemination of
learning, while the irresponsible method of the time, of
appealing to authority on all questions, threw a barrier across
the stream of progress. Intellectuality was not, however,
entirely crushed during the prevalence of these conditions.
The medieval philosophers were masters of the metaphysical
method of argument, and their mentality was by no means
dull. While some branches of learning might make a little
advance, the study of nature suffered the most, for the knowl-
edge of natural phenomena necessitates a mind turned
outward in direct observation of the phenomena of the
natural and physical universe.

Renewal of Observation. — It was an epoch of great im-
portance, therefore, when men began again to observe, and
to attempt, even in an unskilful way, hampered by intellec-
tual inheritance and habit, to unravel the mysteries of nature
and to trace the relation between causes and effects in the
universe. This new movement was a revolt of the intellect
against existing conditions. In it were locked up all the
benefits that have accrued from the development of modern
science. Just as the decline had been due to many causes,
so also the general revival was complex. The invention of
printing, the voyages of mariners, the rise of universities,
and the circulation of ideas consequent upon the Crusades,
all helped to disseminate the intellectual ferment. These
generic influences aided in molding the environment, but,
just as the pause in science had been due to the turning away
from nature and to new mental interests, so the revival was
a return to nature and to the method of science. The pio-

20 BIOLOGY AND ITS MAKERS

neers had to be men of determined independence; they labored
against self-interest as well as opposition from the church
and the priesthood, and they withstood the terrors of the
Inquisition and the loss of recognition and support.

In this uncongenial atmosphere men like Galileo, Des-
cartes, and Vesalius established the new movement and over-
threw the reign of authority. With the coming of \'esalius
the new era of biological progress w^as opened, but its growth
was a slow one; a growth of which we are now to be con-
cerned in tracing the main features.

Forecast of Biological History

It will be helpful to outline the epochs of biological prog-
ress before taking them up for fuller consideration. The
foundation of progress was the renewal of observation in
which, as already stated, all modern science was involved.

It was an epoch in biological history .when Vesalius (1514-
1564) overthrew the authority of Galen, and ^tudied at first
hand the organization of the human body.

It was an epoch when William Harvey (1578-1667), by
adding experiment to observation, demonstrated the circula-
tion of the blood and created a new physiology. The two
coordinate branches of biology were thus early outlined.

The introduction of the microscope in the seventeenth
century, mainly through the labors of Grew, Hooke, Mal-
pighi, and Leeuwenhoek, opened a new world to the investi-
gator, and the work of these men marks an epoch in the prog-
ress of independent inquiry.

Linnaeus (i 707-1 778), by introducing short descriptions
and uniform names for animals and plants, greatly advanced
the subject of natural history.

Cuvier (1769-183 2), by founding the school of compara-

OUTLINE OF BIOLOGICAL PROGRESS 21

live anatomy, so furthered the knowledge of the organization
of animals that he created an epoch.

Bichat (1771-1801) his great contemporary, created an-
other by laying the foundation of our knowledge of the struc-
ture of animal tissues.

Von Baer (1792-1876), by his studies of the development
of animal life, supplied what was lacking in the work of
Cuvier and Bichat and originated modern embryology.

Haller (i 708-1 777), in the eighteenth, and Johannes Miil-
ler (1801-1858) in the nineteenth century, so added to the
ground work of Harvey that physiology was made an inde-
pendent subject and was established on modern lines.

With Buff on, Erasmus, Darwin, and Lamarck (1744-
1829) began an epoch in evolutionary thought which had
its culminating point in the work of Charles Darwin (1869-
1882).

Mendel's experimental observations on inheritance, pub-
lished in 1866, mark one of the most important biological
discoveries of the nineteenth century, although the recogni-
tion of his work was delayed till the year 1901.

After Cuvier and Bichat came the estabhshing of the cell-
theory (1838), which created an epoch and influenced all
further progress.

Finally, through the discovery of protoplasm (1835) and
the recognition that it is the seat of all vital activity, arrived
the epoch (1861) which brought us to the threshold of the
biology of the present day.

Step by step naturalists have been led from the obvious and
superficial facts about living organisms to the deeplying
basis of all vital manifestations.

CHAPTER II

VESALIUS AND THE OVERTHROW OF AUTHORITY
IN SCIENCE

Vesalius, although an anatomist, is to be recognized in a
broad sense as one of the founders of biology. When one
is attempting to investigate animal and plant life, not only
must he become acquainted with the external appearance of
living organisms, but also must acquire early a knowledge
of their structure, without which other facts relating to their
lives can not be disclosed. Anatomy, which is the science
of the structure of organized beings, is therefore so funda-
mental that we find ourselves involved in tracing the history
of its rise as one part of the story of biology. But it is not
enough to know how animals and plants are constructed;
we must also know something about the purpose of the
structures and of the life that courses through them, and,
accordingly, after considering the rise of anatomy, we must
take a similar view of its counterpart, physiology.

The great importance of Vesalius in the history of science
lies in the fact that he overthrew adherence to authority as
the method of ascertaining truth, and substituted therefor
observation and reason. Several of his forerunners had
tried to accomplish the same end, but they had failed. He
was indebted to them as every man is indebted to his fore-
bears, but at the same time we can not fail to see that Vesalius
was worthy of the victory. He was more resolute and force-
ful than any of his predecessors. He was one of those rare

OVERTHROW OF AUTHORITY IN SCIENCE 23

Spirits who see new truth wdth clearness, and have the bravery
to force their thoughts on an unsympathetic public.

The Beginning of Anatomy. — In order to appreciate his
service it is necessary to give a brief account of his predeces-
sors, and of the condition of anatomy in his time. Remem-
bering that anatomy embraces a knov/ledge of the architec-
ture of all animals and plants, we can, nevertheless, see why
in early times it should have had more narrow boundaries.
The m.edical men were the first to take an interest in the
structure of the human body, because a knowledge of it is
necessary for medicine and surgery. It thus happens that
the earliest observations in anatomy were directed toward
making known the structure of the human body and that of
animals somewhat closely related to man in point of struc-
ture. Anatomical studies, therefore, began with the more
complex animals instead of the simpler ones, and, later,
when comparative anatomy began to be studied, this led to
many misunderstandings ; since the structure of man became
the type to which all others were referred, while, on account
of his derivation, his structure presents the greatest modifi-
cation of the vertebrate type.

It was so difficult in the early days to get an opportunity
to study the human body that the pioneer anatomists were
obliged to gain their knowledge by dissections of animals, as
the dog, and occasionally the monkey. In this way Aristotle
and his forerunners learned much about anatomy. About
300 B.C., the dissection of the human body was legalized in
the Alexandrian school, the bodies of condemned criminals
being devoted to that purpose. But this did not become
general even for medical practitioners, and anatomy contin-
ued to be studied mainly from brute animals.

Galen. — The anatomist of antiquity who outshines all
others was Galen (Claudius Galenus, 130-200 a.d.), who lived
some time in Pergamos, and for five years in Rome, during

24 BIOLOGY AND ITS MAKERS

the second century of the Christian era. He was a man of
much talent, both as an observer and as a writer. His de-
scriptions were clear and forceful, and for twelve centuries
his works exerted the greatest influence of those of all scien-
tific writers. In his wTitings was gathered all the anatomical
knowledge of his predecessors, to which he had added ob-
servations of his own. He was a man of originality, but not
having the human body for dissection, he erred in expounding
its structure "on the faith of observations made on lower
animals," He used the right method in arriving at his facts.
Huxley says: " No one can read Galen's works without being
impressed with the marvelous extent and diversity of his
knowledge, and by his clear grasp of those experimental
methods by which alone physiology can be advanced."

Anatomy in the Middle Ages. — But now we shall see how
the arrest of inquiry already spoken of operated in the field
of anatomy. The condition of anatomy in the Middle Ages
was the condition of all science in the same period. From
its practical importance anatomy had to be taught to medical
men, while physics and chemistry, biology and comparative
anatomy remained in an undeveloped state. The way in
which this science was taught is a feature which characterizes
the intellectual life of the Middle Ages. Instead of having
anatomy taught by observations, the writings of Galen were
expounded from the desk, frequently without demonstrations
of any kind. Thus his work came to be set up as the one
unfailing authority on anatomical knowledge. This was in
accord with the dominant ecclesiastical influence of the time.
Reference to authority w^as the method of the theologians,
and by analogy it became the method of all learning. As
the Scriptures v/ere accepted as the unfailing guide to spir-
itual truth, so Galen and other ancient writers were made
the guides to scientific truth and thought. The baneful
effects of this in stifling inquiry and in reducing knowledge

Fig. 3. — Galen, 131-200.
From Acta Medicorvm Berolinensium, 1715.

26 BIOLOGY AND ITS MAKERS

to parrot-like repetition of ancient formulas are so obvious
that they need not be especially dwelt upon.

Predecessors of Vesalius. — Italy gave birth to the first
anatomists who led a revolt against this slavery to authority
in scientific matters. Of the eminent anatomists who pre-
ceded Vesalius it will be necessary to mention only three.
Mundinus, or Mondino, professor at the University of
Bologna, who, in the early part of the fourteenth century,
dissected three bodies, published in 131 5 a work founded
upon human dissection. He was a man of originality whose
work created a sensation in the medical world, but did not
supersede Galen's. His influence, although exerted in the
right direction, was not successful in establishing observation
as the method of teaching anatomy. His book, however,
was sometimes used as an introduction to Galen's writings
or in conjunction with them.

The next man who requires notice is Berengarius of Carpi,
who was a professor in the University of Bologna in the early
part of the sixteenth century. He is said to have dissected
not less than one hundred human bodies ; and although his
opportunities for practical study were greater than those of
Mondino, his attempts to place the science of anatomy upon
a higher level were also unsuccessful.

We pass now from Italy to France where Jacobus Sylvius
(1478-1555), one of the teachers of Vesalius, became distin-
guished as a teacher of anatomy. The work of this man has
been confused with that of Franciscus Sylvius (16 14-167 2),
who lived about a century later in Holland. The recent
analysis of the original sources by Dr. Frank Baker has
served to clear away many misconceptions regarding the
two Sylviuses. Jacobus Sylvius did not investigate the
brain nor were the fissure and artery of Sylvius named in his
honor. On the contrary, Franciscus Sylvius described these
parts for the first time, about 1641, and they bear his name.

OVERTHROW OF AUTHORITY IN SCIENCE 27

The historical association of Jacobus Sylvius with Vesalius
makes it of prime importance to do justice to his services to
anatomy, more especially since Vesalius made indiscriminate
criticisms of his teacher that have generally been accepted
without further testimony. Jacobus Sylvius evidently under-
stood what was essential to a reform in the teaching of anat-
omy, for, in his introduction to anatomy, he is very explicit
in advising that the study be pursued always by eye and
touch and primarily from the human body. He says that
anatomy can never be taught by reading and description.
Nevertheless, the limitations under which he labored, the
lack of sufficiently strong initiative, and the practical diffi-
culty of obtaining material, led him to teach the subject on
a lower level than he theoretically advocated. He read Galen
to his classes and the limited number of dissections in his
lecture room were made usually on the bodies of dogs by
unskilled barbers. With all these limitations, he helped
to elevate the standard of teaching anatomy in France, he
was very clear as an expounder of the subject, and he made
an important contribution in assigning special names to
muscles and bloodvessels. Galen had designated muscles
and other parts by numbers, while Vesalius gave them spe-
cific names, some of which are in use today. He was such a
worshipper of Galen that his method was essentially that of
authority and the progress of science awaited an innovator.

Vesalius. — Vesalius now came upon the scene; and
through his efforts, before he was thirty years of age, the idol
of authority had been shattered, and, mainly through his
persistence, the method of so great moment to future ages
had been established. He was well fitted to do battle against
tradition — strong in body, in mind, and in purpose, gifted
and forceful; and, furthermore, his work was marked by
concentration and by the high moral quahty of fidelity to
truth.

28 BIOLOGY AND ITS MAKERS

Vesalius was bom in Brussels on the last day of the year
1 514, of an ancestry of physicians and learned men, from
whom he inherited his leaning toward scientific pursuits.
Early in hfe he exhibited a passion for anatomy; he dissected
birds, rabbits, dogs, and other animals. Although having
a strong bent in this direction, he was not a man of single
talent. He was schooled in all the learning of his time,
and his earliest publication was a translation from the Greek
of the ninth book of Rhazes. After his early training at
Brussels and at the University of Louvain, in 1533, at the
age of 18, he went to Paris to study medicine, where, in
anatomy, he came under Sylvius and Giinther.

His Force and Independence. — His impetuous nature was
shown in the amphitheatre of Sylvius, where, at the third
lecture, he pushed aside the clumsy surgeon barbers, and
himself exposed the parts as they should be. He could not
be satisfied with the exposition of the printed page ; he must
see with his own eyes, must grasp through his own expe-
rience the facts of anatomical structure. This demand of
his nature shows not only how impatient he was with
sham, but also how much more he was in touch with reality
than were the men of his time.

After three years at the French capital, owing to wars
in Belgium, he went back to Louvain without obtaining his
medical degree. After a short experience as surgeon on the
field of battle, he went to Padua, whither he was attracted
by reports of the opportunities for practical dissection that
he so much desired to undertake. There his talents were
recognized, and just after receiving his degree of Doctor of
Medicine in 1537, he was given a post in surgery, with the
care of anatomy, in the university.

His Reform of the Teaching of Anatomy. — The sympa-
thetic and graphic description of this period of his career by
Sir Michael Foster is so good that I can not refrain from

Fig. 4. — Vesalius, 15 14-1564.

30 BIOLOGY AND ITS MAKERS

quoting it: "He at once began to teach anatomy in his own
new way. Not to unskilled, ignorant barbers would he en-
trust the task of laying bare before the students the secrets of
the human frame; his own hand, and his own hand alone,
was cunning enough to track out the pattern of the structures
which day by day were becoming more clear to him. Fol-
lowing venerated customs, he began his academic labors by
* reading' Galen, as others had done before him, using his
dissections to illustrate what Galen had said. But, time after
time, the body on the table said something different from
that which Galen had written.

''He tried to do what others had done before him — he
tried to believe Galen rather than his own eyes, but his eyes
were too strong for him; and in the end he cast Galen and
his writings to the winds, and taught only what he himself
had seen and what he could make his students see, too.
Thus he brought into anatomy the new spirit of the time,,
and the men of the time, the young men of the time, answered
the new voice. Students flocked to his lectures; his hearers
amounted, it is said, to some five hundred, and an enlightened
senate recognized his worth by repeatedly raising his emol-
uments.

"Five years he thus spent in untiring labors at Padua.
Five years he wrought, not weaving a web of fancied thought,
but patiently disentangling the pattern of the texture of
the human body, trusting to the words of no master, ad-
mitting nothing but that which he himself had seen; and at
the end of the five years, in 1542, while he was as yet not
twenty-eight years of age, he was able to write the dedi-
cation to Charles V of a folio work entitled the ' Structure of
the Human Body,' adorned with many plates and woodcuts
which appeared at Basel in the following year, 1543."

His Physiognomy. — This classic with the Latin title,
De Humani Corporis Fabrica, requires some special notice;.

Fig. 5. — Anatomical Sketch from Vesalius's Fabrica.
(Photographed and reduced from the facsimile edition of 1728.)

32 BIOLOGY AND ITS MAKERS

but first let us have a portrait of Vesalius, the master. Fig. 4
shows a reproduction of the portrait with which his work
is provided. He is represented in academic costume, prob-
ably that which he wore at lectures, in the act of demonstrat-
ing the muscles of the arm. The picture is reduced, and in
the reduction loses something of the force of the original.
We see a strong, independent, self-willed countenance; what
his features lack in refinement they make up in force ; not
an artistic or poetic face, but the face of the man of action
with scholarly training.

His Great Book. — The book of Vesalius laid the founda-
tion of modern biological science. It is more than a land-
mark in the progress of science — it created an epoch. It is
not only interesting historically, but on account of the highly
artistic plates with which it is illustrated it is interesting to
examine by one not an anatomist. For executing the plates
Vesalius secured the service of a fellow-countryman, John
Stephen de Calcar, who was one of the most gifted pupils of
Titian. The drawings are of such high artistic quality that
for a long time they were ascribed to Titian. The artist has
attempted to soften the necessarily prosaic nature of anatom-
ical illustrations by introducing an artistic background of
landscape of varied features, with bridges, roads, streams,
buildings, etc. The employment of a background even in
portrait-painting was not uncommon in the same century,
as in Leonardo da Vinci's well-known Mona Lisa, with its
suggestive perspective of water, rocks, etc.

Fig. 5 will give an idea on a small scale of one of the plates
illustrating the work of Vesalius. The plates in the original
are of folio size, and represent a colossal figure in the fore-
ground, with a background showing between the limbs and
at the sides of the figure. There is considerable variety as
regards the background, no two plates being alike.

Also, in delineating the skeleton, the artist has given to

Fig. 6. — The Skeleton, from Vesalius's Fabrica.

34

BIOLOGY AND ITS MAKERS

it an artistic pose, as is shown in Fig. 6, but nevertheless the
bones are well drawn. No plates of equal merit had ap-
peared before these; in fact, they are the earhest generally

known drawings in anatomy, al-
though woodcuts representing
anatomical figures were pub-
lished as early as 149 1 by John
Ketham. Ketham's figures
showed only externals and pre-
parations for opening the body,
but rude woodcuts representing
internal anatomy and the hu-
man skeleton had been pub-
lished notably by Magnus
Hundt, 1 501; Phrysen, 15 18;
and Berengarius, 1521 and
1523. Leonardo da Vinci and
other artists had also executed
anatomical drawings before the
time of Vesalius.

Previous to the publication
of the complete work, Vesalius,
in 1 538, had published six tables
of anatomy, and, in 1555, he
brought out a new edition of the
Fabrica, with slight additions,
especially in reference to physi-
ology, which will be adverted to
in the chapter on Harvey.

In the original edition of 1543
the illustrations are not col-
lected in the form of plates, but
Fig. 7.— Initial letters from are distributed through the text,
Yesalius's Fabrica oi 1543. the larger ones making full-page

OVERTHROW OF AUTHORITY IN SCIENCE 35

(folio) illustrations. In this edition also the chapters are in-
troduced with an initial letter showing curious anatomical
figures in miniature, some of which are shown in Fig. 7.

The Fahrica of Vesalius was a piece of careful, honest work,
the moral influence of which must not be overlooked. At any
moment in the world's history, work marked by sincerity ex-v
ercises a wholesome influence, but at this particular stage
of intellectual development such work was an innovation, and
its significance for progress was wider and deeper than it
might have been under different circumstances.

Opposition to Vesalius. — The beneficent results of his
efforts were to unfold afterward, since, at the time, his utter-
ances were vigorously opposed from all sides. Not only did
the ecclesiastics contend that he was disseminating false and
harmful doctrine, but the medical men from whom he might
have expected sympathy and support violently opposed his
teachings.

Many amusing arguments were brought forward to dis-
credit VesaKus, and to uphold the authority of Galen.
Vesalius showed that in the human body the lower jaw is
a single bone — that it is not divided as it is in the dog and
other lower mammals, and, as Galen had taught, also in the
human subjects. He showed that the sternum, or breast
bone, has three parts instead of eight; he showed that the
thigh bones are straight and not cui-yed, as they are in the dog.
Sylvius, his old teacher, was one of his bitterest opponents;
he declared that the human body had undergone changes in
structure since the time of Galen, and, with the object of de-
fending the ancient anatomist, " he asserted that the straight
thigh bones, which, as every one sav/, were not curved in
accordance with the teaching of Galen, were the result of
the narrow trousers of his contemporaries, and that they
must have been curved in their natural condition, when un-
interfered with bv art! "

3^ BIOLOGY AND ITS MAKERS

The theologians also found other points for contention.
It was a widely accepted dogma that man should have one
less rib on one side, because from the Scriptural account
Eve was formed from one of Adam's ribs. This, of course,
Vesalius did not find to be the case. It was also generally
believed at this time that there was in the body an indestruc-
tible resurrection-bone which formed the nucleus of the
resurrection-body. Vesalius said that he would leave the
question of the existence of such a bone to be decided by the
theologians, as it did not appear to him to be an anatomical
question.

The Court Physician. — The hand of the church was heavy
upon him, and the hatred shown in attacks from various
quarters threw Vesalius into a state of despondency and
anger. In this frame of mind he destroyed manuscripts upon
which he had expended much labor. His disappointment
in the reception of his work probably had much to do in
deciding him to relinquish his professorship and accept the
post of court physician to Charles V of the United Kingdoms
of Spain and Belgium. After the death of Charles, he
remained with Philip II, who succeeded to the throne. Here
he waxed rich and famous, but he was always under sus-
picion by the clerical powers, who from time to time found
means of discrediting him. The circumstances of his leaving
Spain are not definitely known. One account has it that he
made a post-mortem examination of a body which showed
signs of life during the operation, and that he was required
to undertake a pilgrimage to the Holy Land to clear his soul
of sacrilege. Whether or not this was the reason is uncertain,
but after nineteen years at the Spanish Court he left, in 1563,
and journeyed to Jerusalem. On his return from Palestine
he suffered shipwreck and died from the effects of exposure
on Zanti, one of the Ionian Islands. It is also said that
while on this pilgrimage he had been offered the position of

OVERTHROW OF AUTHORITY IN SCIENCE 37

professor of anatomy as successor to Fallopius, who had
died in 1563, and that, had he lived, he would have come
back honorably to his old post.

Eustachius and Fallopius. — The work of two of his con-
temporaries, Eustachius and Fallopius, requires notice.
Cuvier says in his Histoire des Sciences Naturelles that those
three men were the founders of modern anatomy. Vesalius

Fig. 8. — Fallopius, 1523-1563.

was a greater man than either of the other two, and his
influence was more far-reaching. He reformed the entire
field of anatomy, while the names of Eustachius and Fallopius
are connected especially with a smaller part of the field.
Eustachius described the Eustachian tube of the ear and gave
especial attention to sense organs; Fallopius made special
investigations upon the viscera, and described the Fallopian
tube.

3^ BIOLOGY AND ITS MAKERS

Fallopius was a suave, polite man, who became professor
of anatomy at Padua; he opposed Vesalius, but his attacks
were couched in respectful terms.

Eustachius, the professor of anatomy at R.ome, was of a
different type, a harsh, violent man, who assailed Vesalius
with virulence. He corrected some mistakes of Vesalius,
and prepared new plates on anatomy, which, however, were
not published until 1754, and therefore did not exert the in-
fluence upon anatomical studies that those of Vesalius did.

The Especial Service of Vesalius. — It should be remem-
bered that both these men had the advantage of the sketches
made under the direction of Vesalius. Pioneers and path-
breakers are under special limitations of being in a new
territory, and make more errors than they would in following
another's survey of the same territory; it takes much less
creative force to correct the errors of a first survey than
to make the original discoveries. Everything considered,
Vesalius is deserving of the position assigned to him. He
was great in a larger sense, and it was his researches in
particular which re-established scientific method and made
further progress possible. His errors were corrected, not by
an appeal to authority, but by the method which he founded.
His great claim to renown is, not that his work outshone all
other work (that of Galen in particular) in accuracy and
brilliancy, but that he overthrew dependence on authority
and re-established the scientific method of ascertaining truth.
It was the method of Aristotle and Galen given anew to the
world.

The spirit of progress was now released from bondage,
but we have still a long way to go under its guidance to reach
the gateway of modern biology.

CHAPTER III

WILLIAM HARVEY AND EXPERIMENTAL OBSERVA-
TION

After the splendid observations of Vesalius, revealing in
a new light the construction of the human body. Harvey took
the next general step by introducing experiment to determine
the use or purpose of the structures that Vesalius had so
clearly exposed. Thus the work of Harvey was complemental
to that of Vesalius, and we may safely say that, taken together,
the work of these two men laid the foundations of the modern
method of investigating nature. The results they obtained,
and the influence of their method, are of especial interest to us
in the present connection, inasmuch as they stand at the
beginning of biological science after the Renaissance. Al-
though the observations of both were applied mainly to the
human body, they served to open the entire field of structural
studies and of experimental observations on living organisms.

Many of the experiments of Harvey, notably those relating
to the movements of the heart, were, of course, conducted
upon the lower animals, as the frog, the dog, etc. His ex-
periments on the living human body consisted mainly in
applying ligatures to the arms and the legs. Nevertheless,
the results of all his experiments related to the phenomena of
the circulation in the human body, and were primarily for
the use of medical men.

In what sense the observations of the two men were com-
plemental will be better understood when we remember that
there are two aspects in which living organisms should
always be considered in biological studies; first, the struc-

39

40 BIOLOGY AND ITS MAKERS

ture, and, then, the use that the structures subserve. One
view is essential to the other, and no investigation of animals
and plants is complete in which the two ideas are not in-
volved. Just as a knowledge of the construction of a ma-
chine is necessary to understand its action, so the anatomical
analysis of an organ must precede a knowledge of its office.
The term " physiological anatomy of an organ," so commonly
used in text-books on physiology, illustrates the point. We
can not appreciate the work of such an organ as the liver
without a knowledge of the arrangement of its working units.
The work of the anatomist concerns the statics of the body,
that of the physiologist the dynamics; properly combined,
they give a complete picture of the living organism.

It is to be remembered that the observations of Vesalius
were not confined exclusively to structure; he made some
experiments and some comments on the use of parts of the
body, but his work was mainly structural, while that which
distinguishes Harvey's research is inductions founded on
experimental observation of the action of living tissues.

The service of Vesalius and Harvey in opening the path
to biological advance is very conspicuous, but they were not
the only pioneers ; their work was a part of the general revival
of science in which Galileo, Descartes, and others had their
part. While the birth of the experimental method was not
due to the exertions of Harvey alone, nevertheless it should
stand to his credit that he established that method in bio-
logical lines. Aristotle and Galen both had employed ex-
periments in their researches, and Harvey's step was in the
nature of a revival of the method of the old Greeks.

Harvey's Education. — Harvey was fitted both by native
talent and by his training for the part which he played in the
intellectual awakening. He was bom at Folkestone, on the
south coast of England, in 1578, the son of a prosperous
yeoman. The Harvey family was well esteemed, and the

HARVEY AND EXPERIMENTAL OBSERVATION 41

father of William was at one time the mayor of Folkestone.
Young Harvey, after five years in the King's school at Canter-
bury, went to Cambridge, and in 1593, at the age of sixteen,
entered Caius College. He had already shown a fondness
for observations upon the organization of animals, but it is
unlikely that he was able to cultivate this at the university.
There his studies consisted mainly of Latin and Greek, with
some training in debate and elementary instruction in the
science of physics.

At Padua. — In 1597, at the age of nineteen, he was grad-
uated with the Arts degree, and the following year he turned
his steps toward Italy in search of the best medical instruc-
tion that could be found at that time in all the world. He
selected the great university of Padua as his place of sojourn,
being attracted thither by the fame of some of its medical
teachers. He was particularly fortunate in receiving his
instruction in anatomy and physiology from Fabricius, one
of the most learned and highly honored teachers in Italy.
The fame of this master of medicine, who, from his birth-
place, is usually given the full name of Fabricius ah Aqua-
pendente, had spread to the intellectual centers of the world,
where his work as anatomist and surgeon was especially
recognized. A fast friendship sprang up between the young
medical student and this ripe anatomist, the influence of which
must have been very great in shaping the future work of Harvey.

Fabricius was already sixty-one years of age, and when
Harvey came to Padua was perfecting his knowledge upon
the valves of the veins. The young student was taken fully
into his confidence, and here was laid that first familiarity
with the circulatory system, the knowledge of which Harvey
was destined so much to advance and amplify. But it was
the stimulus of his master's friendship, rather than what he
taught about the circulation, that was of assistance to Harvey.
For the views of Fabricius in reference to the circulation were

42 BIOLOGY AND ITS MAKERS

those of Galen; and his conception of the use of the valves
of the veins was entirely wrong. A portrait of this great
teacher of Harvey is shown in Fig. 9.

At Padua young Harvey attracted notice as a student of
originality and force, and seems to have been a favorite with
the student body as well as with his teachers. His position
in the university may be inferred from the fact that he be-
longed to one of the aristocratic-student organizations, and,
further, that he was designated a " councilor" for England.
The practice of havdng student councilors was then in vogue
in Padua; the students comprising the council met for
deliberations, and very largely managed the university by
their votes upon instructors and university measures.

It is a favorable comment upon the professional education
of his time that, after graduating at the University of Cam-
bridge, he studied four or more years (Willis says five years)
in scientific and medical lines to reach the degree of Doctor
of Physic.

On leaving Padua, in 1602, he returned to England and
took the examinations for the degree of M.D. from Cam-
bridge, inasmuch as the medical degree from an English
university advanced his prospects of receiving a position at
home. He opened practice, was married in 1604, and the
same year began to give public lectures on anatomy.

His Personal Qualities. — Harvey had marked individual-
ity, and seems to have produced a powerful impression upon
those with whom he came in contact as one possessing
unusual intellectual powers and independence of character.
He inspired confidence in people, and it is significant that,
in reference to the circulation of the blood, he won to his way
of thinking his associates in the medical profession. This is
important testimony as to his personal force, since his ideas
were opposed to the belief of the time, and since also away
from home they were vigorously assailed.

Fig. 9. — Fabricius, 1537-1619, Harvey's Teacher.

44

BIOLOGY AND ITS MAKERS

Although described as choleric and hasty, he had also
winning qualities, so that he retained warm friendships
throughout his life, and was at all times held in high respect.

Fig. io. — William Harvey, 1578-1667.

It must be said also that in his replies to his critics, he showed
great moderation.

The contemplative face of Harvey is shown in Fig. 10.
This is taken from his picture in the National Portrait
Gallery in London, and is usually regarded as the second-

HARVEY AND EXPERIMENTAL OBSERVATION 45

best portrait of Harvey, since the one painted by Jansen,
now in possession of the Royal College of Physicians, is
believed to be the best one extant. The picture reproduced
here shows a countenance of composed intellectual strength,
with a suggestion, in the forehead and outline of the face, of
some of the portraits of Shakespeare.

x\n idea of his personal appearance may be had from the
description of Aubrey, who says : '' Harvey was not tall, but of
the lowest stature; round faced, with a complexion like the
wainscot ; his eyes small, round, very black, and full of spirit ;
his hair black as a raven, but quite white twenty years before
he died; rapid in his utterance, choleric, given to gesture,"
etc.

He was less impetuous than Vesalius, who had published
his work at twenty-eight; Harvey had demonstrated his ideas
of the circulation in public anatomies and lectures for twelve
years before publishing them, and when his great classic on
the Movement of the Heart and Blood first appeared in 1628,
he was already fifty years of age. This is a good example for
young investigators of to-day who, in order to secure priority
of announcement, so frequently rush into print wnth imperfect
observations as preliminary communications.

Harvey's Writings. — Harvey's publications were all great ;
in embryology, as in physiology, he produced a memorable
treatise. But his publications do not fully represent his
activity as an investigator; it is known that through the
fortunes of war, while connected with the sovereign Charles I.
as court physician, he lost manuscripts and drawings upon
the comparative anatomy and development of insects and
other animals. His position in embryology will be dealt
w^ith in the chapter on the Development of Animals, and he
will come up for consideration again in the chapter on the
Rise of Physiology. Here we are concerned chiefly with his
general influence on the development of biology.

46 BIOLOGY AND ITS MAKERS

His Great Classic on Movement of the Heart and Blood.

— Since his book on the circulation of the blood is regarded
as one of the greatest monuments along the highroad of biol-
og)% it is time to make mention of it in particular. Although
relatively small, it has a long title out of proportion to its
size: Exercitatio Anatomica de Motu Cordis et Sanguinis in
Animalibus, which maybe freely translated, '^ An Anatomical
Disquisition on the Movement of the Heart and Blood in
Animals." The book is usually spoken of under the shorter
title, De Motu Cordis et Sanguinis. The full title seems some-
what repellent, but the contents of the book will prove to be
interesting to general readers. It is a clear, logical demon-
stration of the subject, proceeding with directness from one
point to another until the culminating force of the argument
grows complete and convincing.

The book in its first edition was a quarto volume of
seventy-eight pages, published in Frankfort in 1628. An
interesting facsimile reprint of this work, translated into
English, was privately reproduced in 1894 by Dr. Moreton
and published in Canterbury. As stated above, it is known
that Harvey had presented and demonstrated his views in
his lectures since 161 6. In his book he showed for the first
time ever in print, that all the blood in the body moves in a
circuit, and that the beating of the heart supplies the propel-
ling force. Both ideas were new, and in order to appreciate
in what sense they were original with Harvey, we must
inquire into the views of his forerunners.

Question as to Harvey's Originality. — The question of
how near some of his predecessors came to anticipating his
demonstration of the circulation has been much debated.
It has been often maintained that Servetus and Realdus
Columbus held the conception of the circulation for which
Harvey has become so celebrated. Of the various accounts
of the views of Harvey's predecessors, those of Willis, Huxley,

HARVEY AND EXPERIMENTAL OBSERVATION 47

and Michael Foster are among the most judicial; that of
Foster, indeed, inasmuch as it contains ample quotations
from the original sources, is the most nearly complete and
satisfactory. The discussion is too long to enter into fully
here, but a brief outline is necessary to understand what
he accomplished, and to put his discovery in the proper
light.

To say that he first discovered — or, more properly,
demonstrated—the circulation of the blood carries the im-
pression that he knew of the existence of capillaries connect-
ing the arteries and the veins, and had ocular proof of the
circulation through these connecting vessels. But he did not
actually see the blood moving from veins to arteries, and he
knew not of the capillaries. He understood clearly from his
observations and experiments that all the blood passes from
veins to arteries and moves in "a kind of circle"; still, he
thought that it filters through the tissues in getting from one
kind of vessel to the other. It was reserved for Malpighi,
in 1 66 1, and Leeuwenhoek, in 1669, to see, with the aid of
lenses, the movement of the blood through the capillaries
in the transparent parts of animal tissues. (See under
Leeuwenhoek, p. 84.)

The demonstration by Harvey of the movement of the
blood in a circuit was a matter of cogent reasoning, based on
experiments with ligatures, on the exposure of the heart in
animals and the analysis of its movements. It has been com-
monly maintained (as by Whewell) that he deduced the cir-
culation from observations of the valves in the veins, but this
is not at all the case. The central point of Harvey's reason-
ing is that the quantity of blood which leaves the left cavity
of the heart in a given space of time makes necessary its
return to the heart, since in a half-hour (or less) the heart,
by successive pulsations, throws into the great artery more
than the total quantity of blood in the body. Huxley points

48 BIOLOGY AND ITS MAKERS

out that this is the first time that quantitative determinations
were introduced into physiology.

Views of His Predecessors on the Movement of the Blood.

■ — Galen's view of the movement of the blood was not com-
pletely replaced until the establishment of Harvey's view.
The Greek anatomist thought that there was an ebb and flow
of blood within both veins and arteries throughout the
system. The left side of the heart was supposed to contain
blood vitalized by a mixture of animal spirits within the lungs.
The veins were thought to contain crude blood. He sup-
posed, further, that there was a communication between the
right and the left side of the heart through ver}^ minute pores
in the septum, and that some blood from the right side passed
through the pores into the left side and there became charged
with animal spirits. It should also be pointed out that Galen
believed in the transference of some blood through the lungs
from the right to the left side of the heart, and in this fore-
shadowed the views which were later developed by Servetus
and Realdus Columbus.

Vesalius, in the first edition of his work (1543) expressed
doubts upon the existence of pores in the partition-wall of
the heart through which blood could pass ; and in the second
edition (1555) of the Fabrica he became more skeptical.
In taking this position he attacked a fundamental part of
the belief of Galen. The careful structural studies of Vesalius
must have led him very near to an understanding of the con-
nection between arteries and veins. Fig. 11 shows one of
his sketches of the arrangement of arteries and veins. He
saw that the minute terminals of arteries and veins came very
close together in the tissues of the body, but he did not grasp
the meaning of the observation, because his physiology was
still that of Galen; Vesalius continued to believe that the
arteries contained blood mixed with spirits, and the veins
crude blood, and his idea of the movement was that of an

HARVEY AND EXPERIMENTAL OBSERVATION 49

ebb and flow. In reference to the anatomy of the blood-
vessels, he goes so far as to say of the portal vein and the
vena cava in the liver that " the extreme ramifications of these
vems inosculate with each other, and in many places appear

Fig.

-Scheme of the Portal Circulation According
to Vesalius, 1543.

to unite and be continuous." All who followed him had the
advantage of his drawings showing the parallel arrangement
of arteries and veins, and their close approach to each other
in their minute terminal twigs, but no one before Harvey

50 BIOLOGY AND ITS MAKERS

fully grasped the idea of the movement of the blood in a
complete circuit.

Servetus, in his work on the Restoration of Christianity
{Restitutio Christianismi, i553)) the work for which Calvin
accomplished his burning at the stake, expressed more
clearly than Galen had done the idea of a circuit of blood
through the lungs. According to his view, some of the blood
took this course, while he still admits that a part may exude
through the wall of the ventricle from the right to the left
side. This, however, was embodied in a theological treatise,
and had little direct influence in bringing about an altered
view of the circulation. Nevertheless, there is some reason
to think that it may have been the original source of the ideas
of the anatomist Columbus, as the studies into the character
of that observer by Michael Foster seem to indicate.

Realdus Columbus, professor of anatomy at Rome, ex-
pressed a conception almost identical with that of Servetus,
and as this was in an important work on anatomy, published
in 1559, and well known to the medical men of the period,
it lay in the direct line of anatomical thought and had greater
influence. Foster suggests that the devious methods of
Columbus, and his unblushing theft of intellectual property
from other sources, give ground for the suspicion that he had
appropriated this idea from Servetus without acknowledg-
ment. Although Calvin supposed that the complete edition
of a thousand copies of the work of Servetus had been burned
with its author in 1553, a few copies escaped, and possibly
one of these had been examined by Columbus. This as-
sumption is strengthened by the circumstance that Columbus
gives no record of observations, but almost exactly repeats
the words of Servetus.

Caesalpinus, the botanist and medical man, expressed in
1 571 and 1593 similar ideas of the movement of the blood
(probably as a matter of argument, since there is no record

HARVEY AND EXPERIMENTAL OBSERVATION 5^

of either observations or experiments by him). He also laid
hold of a still more important conception, viz., that some of
the blood passes from the left side of the heart through the
arteries of the body, and returns to the right side of the heart
by the veins. But a fair consideration of the claims of these
men as forerunners of Harvey requires quotations from their
works and a critical examination of the evidence thus adduced.
This has been excellently done by Michael Foster in his Lec-
tures on the History of Physiology. Further considerations
of this aspect of the question would lie beyond the purposes
of this book.

At most, before Harvey, the circuit through the lungs had
been vaguely divined by Galen, Servetus, Columbus, and
Caesalpinus, and the latter had supposed some blood to pass
from the heart by the arteries and to return to it by the veins;
but no one had arrived at an idea of a complete circulation
of all the blood through the system, and no one had grasped
the consequences involved in such a conception. Harvey's
idea of the movement of the heart (De Motu Cordis) was new;
his notion of the circulation {et Sanguinis) was new; and
his method of demonstrating these was new.

Harvey's Argument. — The gist of Harvey's arguments is
indicated in the following propositions quoted with slight
modifications from Hall's Physiology: (I) The heart pas-
sively dilates and actively contracts ; (II) the auricles contract
before the ventricles do; (III) the contraction of the auricles
forces:, the blood into the ventricles; (IV) the arteries have
no ^'pulsific power," i.e., they dilate passively, since the pul-
sation of the arteries is nothing else than the impulse of the
blood within them ; (V) the heart is the organ of propulsion
of the blood ; (VI) in passing from the right ventricle to the
left auricle the blood transudes through the parenchyma of
the lungs ; (VII) the quantity and rate of passage of the blood
peripherally from the heart makes it a physical necessity that

52 BIOLOGY AND ITS MAKERS

most of the blood return to the heart ; (VIII) the blood does
return to the heart by way of the veins. It will be noticed
that the proposition VII is the important one; in it is
involved the idea of applying measurement to a physiological
process.

Harvey's Influence. — Harvey was a versatile student.
He was a comparative anatomist as well as a physiologist
and embryologist ; he had investigated the anatomy of about
sixty animals and the embryology of insects as well as of
vertebrates, and his general influence in promoting biological
work was extensive.

His work on the movement of the blood was more than
a record of a series of careful investigations; it was a land-
mark in progress. When we reflect on the part played in
the body by the blood, we readily see that a correct idea of
how it carries nourishment to the tissues, and how it brings
away from them the products of disintegrated protoplasm is
of prime importance in physiology. It is the point from
which spring all other ideas of the action of tissues, and until
this was known the fine analysis of vital processes could not
be made. The true idea of respiration, of the secretion by
glands, the chemical changes in the tissues, in fact, of all the
general activities of the body, hinge upon this conception.
It was these consequences of his demonstration, rather than
the fact that the blood moves in a circuit, which made it so
important. This discovery created modem physiology, and
as that branch of inquiry is one of the parts of general biology,
the bearing of Harvey's discovery upon biological thought
can be readily surmised.

Those who wish to examine Harvey's views at first hand,
without the burden of translating them from the Latin, will
find an edition of his complete works translated into English
by Willis, and published by the Ray Society, of London.

As is always the case with new truths, there was hostility

HARVEY AND EXPERIMENTAL OBSERVATION 53

to accepting his views. In England this hostility was slight
on account of his great personal influence, but on the Conti-
nent there was many a sharp criticism passed upon his work.
His views were so illuminating that they were certain of
triumph, and even in his lifetime were generally accepted.
Thus the new conception of vital activities, together with his
method of inquiry, became permanent parts of biological
science.

CHAPTER IV

THE INTRODUCTION OF THE MICROSCOPE AND
THE PROGRESS OF INDEPENDENT OBSERVATION

The introduction of the microscope greatly increased the
ocular powers of observers, and, in the seventeenth century,
led to many new departures. By its use the observations
were carried from the plane of gross anatomy to that of
minute structure; the anatomy of small forms of life, like in-
sects, began to be studied, and also the smaller microscopic
animalcula were for the first time made known.

Putting aside the disputed questions as to the time of the
invention and the identity of the inventor of the microscope —
whether to Fontana, Galileo, or the Jenssens belongs the
credit — we know that it was improved by the Hollander
Drebbel in the early years of the seventeenth century, but
was not seriously applied to anatomical studies till after the
middle of that century.

«
The Pioneer Microscopists

The names especially associated with early microscopic
observations are those of Hooke and Grew in England,
Malpighi in Italy, and Swammerdam and Leeuwenhoek,
both in Holland. Their microscopes were imperfect, and
were of two kinds : simple lenses, and lenses in combination,
forming what we now know as the compound microscope.
Some forms of these early microscopes will be described and
illustrated later. Although thus early introduced, micro-

54

INTRODUCTION OF THE MICROSCOPE

55

scopic observation did not produce its great results until the
nineteenth century, just after magnifying-lenses had been
greatly improved.

Robert Hooke (1635-1703), of London, published in 1665
a book of observations with the microscope entitled Micro-
graphia, which was embellished with eighty- three plates of
figures. Hooke was a man of fine mental endowment, who
had received a good scientific
training at the University of
Cambridge, but who lacked
fixedness of purpose in the
employment of his talents.
He did good work in math-
ematics, made many models
for experimenting with flying
machines, and claimed to have
discovered gravitation before

Fig. 12. — Hooke's Microscope, 1665.

From Carpenter's T/ie Microscope and Its Revelations. Permission of
P. Blakiston's Sons & Co.

56 BIOLOGY AND ITS MAKERS

Newton, and also the use of a spring for regulating watches
before Huygens, etc. He gave his attention to microscopic
study for a time and then dropped it ; yet, although we can not
accord to him a prominent place in the history of biology,
he must receive mention as a pioneer worker with the micro-
scope. His book gave a powerful stimulus to microscopy in
England, and, partly through its influence, labor in this field
was carried on more systematically by his fellow-countryman
Nehemiah Grew.

The form of the microscope used by Hooke is known
through a picture and a description which he gives of it
in his Micro graphia. Fig. 1 2 is a copy of the illustration.
His was a compound microscope consisting of a combination
of lenses attached to a tube, one set near the eye of the ob-
server and the other near the object to be examined. When
we come to describe the microscopes of Leeuwenhoek, with
which so much good work was accomplished, we shall see
that they stand in marked contrast, on account of their sim-
plicity, to the somewhat elaborate instrument of Hooke.

Grew (1628-1711) devoted long and continuous labor to
microscopic observation, and, although he was less versatile
and brilliant than Hooke, his patient investigations give him
just claim to a higher place in the history of natural science.
Grew applied the microscope especially to the structure of
plants, and his books entitled Idea oj a Philosophical His-
tory of Plants (1673) and Anatomy of Vegetables (1682)
helped to lay the foundations of vegetable histology. When
we come to consider the work of Malpighi, we shall see that
he also produced a work upon the microscopic structure of
plants which, although not more exact and painstaking than
Grew's, showed deeper comprehension. He is the co-
founder with Grew of the science of the microscopic anatomy
of plants.

It IS not necessary to dwell long upon the work of either

INTRODUCTION OF THE MICROSCOPE 57

Hooke or Grew, since that of Malpighi, Swammerdam, and
Leeuwenhoek was more far-reaching in its influence. The
publications of these three men were so important, both in
reference to microscopic study and to the progress of inde-
pendent investigation, that it will be necessary to deal with
them in more detail. In the work of these men we come
upon the first fruits of the application of the methods intro-
duced by Vesalius and Harvey. Of this triumvirate, one —
Malpighi — was an Italian, and the other two were Holland-
ers. Their great service to intellectual progress consisted
chiefly in this — that, following upon the foundations of
Vesalius and Harvey, " they broke away from the thraldom
of mere book-learning, and relying alone upon their own
eyes and their own judgment, won for man that which had
been quite lost — the blessings of independent and unbiased
observation."

It is natural that, working when they did, and independ-
ently as they did, their work overlapped in many ways.
Malpighi is noteworthy for many discoveries in anatomical
science, for his monograph on the anatomy of the silkworm,
for observations of the minute structure of plants, and of the
development of the chick in the hen's egg. Swammerdam
did excellent and accurate work upon the anatomy and
metamorphosis of insects, and the internal structure of mol-
lusks, frogs, and other animals. Leeuwenhoek is distin-
guished for much general microscopic work; he discovered
various microscopic animalcula; he established, by direct
observation, the fact of a connection between arteries and
veins, and examined microscopically minerals, plants, and
animals. To him, more than to the others, the general title
of " microscopist " might be applied.

Since these men are so important in the growth of biol-
ogy, let us, by taking them individually, look a Httle more
closely into their Hves and labors.

58 BIOLOGY AND ITS MAKERS

Marcello Malpighi, 1628-1694

Personal Qualities. — There are several portraits of Mal-
pighi extant. These, together with the account of his
personal appearance given by Atti, one of his biographers,
enable us to tell what manner of man he was. The portrait
shown in Fig. 13 is a copy of the one painted by Tabor and
presented by Malpighi to the Royal Society of London, in
whose rooms it may still be seen. This shows him in the
full attractiveness of his early manhood, with the earnest,
intellectual look of a man of high ideals and scholarly tastes,
sweet-tempered, and endowed with the insight that belongs
to a sympathetic nature. Some of his portraits taken later
are less attractive, and the lines and wrinkles that show
in his face give evidence of imperfect health. According to
Atti, he was of medium stature, with a brown skin, a delicate
complexion, a serious countenance, and a melancholy look.

Accounts of his life show that he was modest, quiet, and
of a pacific disposition, notwithstanding the fact that he lived
in an atmosphere of acrimonious criticism, of jealousy and
controversy. A family dispute in reference to the boundary-
lines between his father's property and the adjoining land of
the Sbaraglia family gave rise to a feud, in which representa-
tives of the latter family followed him all his Kf e with efforts
to injure both his scientific reputation and his good name.
Under all this he suffered acutely, and his removal from
Bologna to Messina was partly to escape the harshness of
his critics. Some of his best qualities showed under these
persecutions; he was dignified under abuse and considerate
in his reply. In reference to the attacks upon his scientific
standing, there were published after his death replies to his
critics that were written while he was smarting under their
injustice and severity, but these replies are free from bitterness
and are written in a spirit of great moderation. The follow-

Fig. 13. — Malpighi, 1628-1694.

6o BIOLOGY AND ITS MAKERS

ing picture, taken from Ray's correspondence, shows the fine
control of his spirit. Under the date of April, 1684, Dr.
Tancred Robinson writes : " Just as I left Bononia I had a
lamentable spectacle of Malpighi's house all in flames,
occasioned by the negligence of his old wife. All his pic-
tures, furniture, books, and manuscripts were burnt. I saw
him in the very heat of the calamity, and methought I never
beheld so much Christian patience and philosophy in any
man before; for he comforted his wife and condoled nothing
but the loss of his papers."

Education. — Malpighi was born at Crevalcuore, near
Bologna, in 1628. His parents were landed peasants, or
farmers, enjoying an independence in financial matters. As
their resources permitted it, they designed to give Marcellus,
their eldest child, the advantage of masters and schools.
He began a life of study; and, before long, he showed a taste
for belles-lettres and for philosophy, which he studied under
Natali.

Through the death of both parents, in 1649, Malpighi
found himself orphaned at the age of twenty-one, and as he
was the eldest of eight children, the management of domestic
affairs devolved upon him. He had as yet made no choice
of a profession ; but, through the advice of Natali, he resolved,
in 165 1, to study medicine. This advice followed, in 1653,
at the age of twenty-five, he received from the University of
Bologna the degree of Doctor of Medicine.

University Positions. — In the course of a few years he
married the sister of Massari, one of his teachers in anatomy,
and became a candidate for a chair in the University of
Bologna. This he did not immediately receive, but, about
1656, he was appointed to a post in the university, and began
his career as a teacher and investigator. He must have
shown aptitude for this work, for he was soon called to the
University of Pisa, where, fortunately for his development,

INTRODUCTION OF THE MICROSCOPE 6l

he became associated with BoreUi, who, as an older man,
assisted him in many ways. They united in some work, and
together they discovered the spiral character of the heart
muscles. But the climate of Pisa did not agree with him,
and after three years he returned, in 1659, to teach in the
University of Bologna, and applied himself assiduously to
anatomy.

Here his fame was in the ascendant, notwithstanding the
machinations of his enemies and detractors, led by Sbaraglia.
He was soon (1662) called to Messina to follow the famous
Castelli. After a residence there of four years he again
returned to Bologna, and as he was now thirty-eight years
of age, he thought it time to retire to his villa near the city
in order to devote himself more fully to anatomical studies,
but he continued his lectures in the university, and also his
practice of medicine.

Honors at Home and Abroad. — Malpighi's talents were
appreciated even at home. The University of Bologna hon-
ored him in 1686 with a Latin eulogium; the city erected a
monument to his memory; and after his death, in the city of
Rome, his body was brought to Bologna and interred with
great pomp and ceremony. At the three hundredth anniver-
sary of his death, in 1894, a festival was held in Bologna,
his monument was unveiled, and a book of addresses by
eminent anatomists was published in his honor.

During his lifetime he received recognition also from
abroad, but that is less remarkable. In 1668 he was elected
an honorary member of the Royal Society of London. He
was very sensible of this honor; he kept in communication
with the society; he presented them with his portrait, and
deposited in their archives the original drawings illustrating
the anatomy of the silkworm and the development of the chick.

In 1 691 he was taken to Rome by the newly elected pope,
Innocent XII, as his personal physician, but under these new

62 BIOLOGY AND ITS MAKERS

conditions he was not destined to live many years. He died
there, in 1694, of apoplexy. His wife, of whom it appears
that he was very fond, had died a short time previously.
Among his posthumous works is a sort of personal psychology
written down to the year 1691, in which he shows the growth
of his mind, and the way in which he came to take up the
different subjects of investigation.

In reference to his discoveries and the position he occupies
in the history of natural science, it should be observed that
he was an " original as well as a very profound observer."
While the ideas of anatomy were still vague, " he applied him-
self with ardor and sagacity to the study of the fine structure
of the different parts of the body," and he extended his inves-
itgations to the structure of plants and of different animals,
and also to their development. Entering, as he did, a new
and unexplored territory, naturally he made many discover-
ies, but no man of mean talents could have done his work.

Activity in Research. — During forty years of his life he
was always busy with research. Many of his discoveries had
practical bearing on the advance of anatomy and physiology
as related to medicine. In 1661 he demonstrated the struc-
ture of the lungs. Previously these organs had been regarded
as a sort of homogeneous parenchyma. He showed the pres-
ence of air-cells, and had a tolerably correct idea of how the
air and the blood are brought together in the lungs, the two
never actually in contact, but always separated by a mem-
brane. These discoveries were first made on the frog, and
applied by analogy to the interpretation of the lungs of the
human body. He was a comparative anatomist, and the
first to insist on analogies of structure between organs
throughout the animal kingdom, and to make extensive
practical use of the idea that discoveries on simpler animals
can be utilized in interpreting the similar structures in the
higher ones.

INTRODUCTION OF THE MICROSCOPE 63,

It is very interesting to note that in connection with this,
work he actually observed the passage of blood through the
capillaries of the transparent lungs of the frog, and also in
the mesenter)\ Although this antedates the similar obser-
vations of Leeuwenhoek (1669), nevertheless the work of
Leeuwenhoek was much more complete, and he is usually
recognized in physiology as the discoverer of the capillary
connection between arteries and veins. At this same period
^lalpighi also observed the blood corpuscles.

Soon after he demonstrated the mucous layer, or pigment-
ary layer of the skin, intermediate between the true and the
scarf skin. He had separated this layer by boiling and
maceration, and described it as a reticulated membrane..
Even its existence was for a long time controverted, but it
remains in modern anatomy under the title of the Malpighian.
kyer.

His observation of glands was extensive, and while it must
be confessed that many of his conclusions in reference to.
glandular structure were erroneous, he left his name connected
with the Malpighian corpuscles of the kidney and of the
spleen. He was also the first to indicate the nature of the
papillae on the tongue. The foregoing is a respectable list of
discoveries, but much more stands to his credit. Those which
follow have a bearing on comparative anatomy, zoology, and
botany.

Monograph on the Structure and Metamorphosis of the
Silkworm. — Malpighi's work on the structure of the silkworm
takes rank among the most famous monographs on the
anatomy of a single animal. Much skill was required to
give to the world this picture of minute structure. The mar-
vels of organic architecture were being made known in the
human body and the higher animals, but ''no insect — ^hardly,
indeed, any animal — had then been carefully described, and
all the methods of the work had to be discovered." He

64 BIOLOGY AND ITS MAKERS

labored with such enthusiasm in this new territory as to throw
himself into a fever and to set up an inflammation in the eyes.
"Nevertheless," says Malpighi, " in performing these re-
searches so many marvels of nature were spread before my
eyes that I experienced an internal pleasure that my pen
could not describe."

He showed that the method of breathing was neither by
lungs nor by gills, but through a system of air-tubes, com-
municating with the exterior through buttonhole shaped
openings, and, internally, by an infinitude of branches reach-
ing to the minutest parts of the body. Malpighi showed an
instinct for comparison; instead of confining his researches
to the species in hand, he extended his observations to other
insects, and has given sketches of the breathing-tubes, held
open by their spiral thread, taken from several species.

The nervous system he found to be a central white cord
with swellings in each ring of the body, from which nerves
are given off to all organs and tissues. The cord, which is, of
course, the central nervous system, he found located mainly
on the ventral surface of the body, but extending by a sort
of collar of nervous matter around the oesophagus, and on
the dorsal surface appearing as a more complex mass, or
brain, from which nerves are given off to the eyes and other
sense organs of the head. As illustrations from this mono-
graph we have, in Fig. 14, reduced sketches of the drawings
of the nervous system and the food canal in the adult silk-
worm. The sketch at the right hand illustrates the central
nerve cord with its ganglionic enlargement in each segment,
the segments being indicated by the rows of spiracles at the
sides. The original drawing is on a much larger scale,
and reducing it takes away some of its coarseness. All
of his drawings lack the finish and detail of Swammerdam's
work.

He showed also the food canal and the tubules connected

INTRODUCTION OF THE MICROSCOPE

6S

with the intestine, which retain his name in the insect anatomy
of to-day, under the designation of Malpighian tubes. The
silk-forming apparatus was also figured and described. These

Fig. 14. — From Malpighi's Anatomy of the Silkworm, 1669.

structures are represented, as Malpighi drew them, on the
left of Fig. 14.

This monograph, which was originally published in 1669
by the Royal Society of London, bears the Latin title, Disser-
laiio Epistolica de Bombyce. It has been several times re-
published, the best edition being that in French, which dates
S

66 BIOLOGY AND ITS MAKERS

from MoRtpellier, in 1878, and which is prefaced by an
account of the life and labors of Malpighi.

Anatomy of Plants. — Malpighi's anatomy of plants con-
stitutes one of his best, as well as one of his most extensive
works. In the folio edition of his works, 1675-79, the
Anatome Plantarum occupies not less than 152 pages and
is illustrated by ninety-three plates of figures. It comprises
an exposition of the structure of bark, stem, roots, seeds, the
process of germination, and includes a treatise on galls, etc.,
etc.

In this work the microscopic structure of plants is amply
illustrated, and he anticipated to a certain degree the ideas on
the cellular structure of plants. Burnett says: "His obser-
vations appear to have been very accurate, and not only did
he maintain the cellular structure of plants, but also declared
that it was composed of separate cells, which he designated
' utricles.' " Thus did he foreshadow the cell theory of plants
as developed by Schleiden in the nineteenth century. When
it came to interpretations, he made several errors. Applying
his often-asserted principle of analogies, he concluded that
the vessels of plants are organs of respiration and of circula-
tion, from a certain resemblance that they bear to the breath-
ing-tubes of insects. But his observations on structure are
good, and if he had accomplished nothing more than this
work on plants he would have a place in the history of botany.

Work in Embryology. — Difficult as was his task in insect
anatomy and plant histology, a more difficult one remains to
be mentioned, viz., his observations of the develo])ment of
animals. He had pushed his researches into the finer struc-
ture of organisms, and now he attempted to answer this
question: How does one of these organisms begin its life,
and by what series of steps is its body built up? He turned
to the chick, as the most available form in which to get an
insight into this process, but he could not extend his obser-

INTRODUCTION OF THE MICROSCOPE 67

vations successfully into periods earlier than about the
twenty-four-hour stage of development. Two memoirs were
written on this subject, both in 1672, which were published
by the Royal Society of England under the titles De Forma-
tione Pulli in Ovo and De Ovo Incubato. Of all Malpighi's
work, this has received the least attention from reviewers,
but it is, for his time, a very remarkable achievement. No
one can look over the ten folio plates without being impressed
wdth the extent and accuracy of his observations. His
sketches arc of interest, not only to students of embryology,
but also to educated people, to see how far observations
regarding the development of animals had progressed in 1672.
Further consideration of his position in embryology will be
found in the chapter on the rise of that subject.

Little is known regarding the form of microscope em-
ployed by Malpighi. Doubtless, much of his work was done
wdth a simple lens, since he speaks of examining the dried
lungs with a microscope of a single lens against the hori-
zontal sun; but he is also known to have observed with an
instrument consisting of two lenses.

Malpighi was a naturalist, but of a new type; he began to
look below the surface, and essayed a deeper level of analysis
in observing and describing the internal and minute structure
of animals and plants, and when he took the further step of
investigating their development he was anticipating the work
of the nineteenth century.

Jan Swammerdam (163 7-1 680)

Swammerdam was a different type of man— nervous,
incisive, very intense, stubborn, and self-willed. Much of his
character shows in the portrait by Rembrandt represented
in Fig. 15. Although its authenticity has been questioned,
it is the only known portrait of Swammerdam.

68 BIOLOGY AND ITS MAKERS

Early Interest in Natural History. — He was born in 1637,
nine years after Malpighi. His father, an apothecary of Am-
sterdam, had a taste for collecting, which was shared by many
of his fellow-townsmen. The Dutch people of this time
sent their ships into all parts of the world, and this vast com-
merce, together with their extensive colonial possessions,
fostered the formation of private museums. The elder
Swammerdam had the finest and most celebrated collection
in all Amsterdam. This was stored, not only with treasures,
showing the civilization of remote countries, but also with
specimens of natural history, for which he had a decided
liking. Thus ''from the earliest dawn of his understanding
the young Swammerdam was surrounded by zoological
specimens, and from the joint influence, doubtless, of hered-
itary taste and early association, he became passionately
devoted to the study of natural history."

Studies Medicine. — His father intended him for the
church, but he had no taste for theology, though he became
a fanatic in religious matters toward the close of his life;
at this period, however, he could brook no restraint in word
or action. He consented to study medicine, but for some
reason he was twenty-six years old before entering the Uni-
versity of Leyden. This delay was very likely owing to his
precarious health, but, in the mean time, he had not been idle;
he had devoted himself to observation and study with great
ardor, and had already become an expert in minute dissec-
tion. When he went to the University of Leyden, therefore,
he at once took high rank in anatomy. Anything demanding
fine manipulation and dexterity was directly in his line. He
continued his studies in Paris, and about 1667 took his degree
of Doctor of Medicine.

During this period of medical study he made some rather
important observations in human anatomy, and introduced
the method of injection that was afterward claimed bv

Fig. 15. SWAMMERDAM, 1637-1680.

70 BIOLOGY AND ITS MAKERS

Ruysch. In 1664 he discovered the valves of lymphatic
vessels by the use of slender glass tubes, and, three years
later, first used a waxy material for injecting blood-vessels.

It should be noted, in passing, that Swammerdam was the
first to observe and describe the blood corpuscles. As early
as 1658 he described them* in the blood of the frog, but not
till fifty-seven years after his death were his observations
published by Boerhaave, and, therefore, he does not get the
credit of this discovery. Publication alone, not first observa-
tion, establishes priority, but there is conclusive evidence
that he observed the blood corpuscles before either Malpighi
or Leeuwenhoek had published his findings.

Love of Minute Anatomy. — ^After graduating in medi-
cine he did not practice, but followed his strong inclination
to devote himself to minute anatomy. This led to differences
with his father, who insisted on his going into practice, but
the self-willed stubbornness and firmness of the son now
shov/ed themselves. It was to gratify no love of ease that
Swammerdam thus held out against his father, but to be
able to follow an irresistible leading toward minute anatomy.
At last his father planned to stop supplies, in order to force
him into the desired channel, but Swammerdam made efforts,
without success, to sell his own personal collection and pre-
serve his independence. His father died, leaving him suffi-
cient property to live on, and brought the controversy to a
close soon after the son had consented to yield to his wishes.

Boerhaave, his fellow-countryman, gathered Swammer-
dam's complete writings after his death and published them
in 1737 under the title Bihlia Naturce. With them is in-
cluded a life of Swammerdam, in which a graphic account is
given of his phenomenal industry, his intense application, his
methods and instruments. Most of the following passages
are selected from that work.

Intensity as a Worker. — He was a very intemperate

INTRODUCTION OF THE MICROSCOPE 7^

worker, and in finishing his treatise on bees (1673) ^^ broke
himself down.

"It was an undertaking too great for the strongest con-
stitution to be continually employed by day in making obser-
vations and almost as constantly engaged by night in record-
ing til em by drawings and suitable explanations. This being
summer work, his daily labors began at six in the morning,
when the sun afforded him light enough to enable him to
survey such minute objects; and from that time till twelve
he continued without interruption, all the while exposed in
the open air to the scorching heat of the sun, bareheaded,
for fear of interrupting the light, and his head in a manner
dissolving into sw^eat under the irresistible ardors of that
powerful luminary. And if he desisted at noon, it was only
because the strength of his eyes was too much weakened by
the extraordinary efflux of light and the use of microscopes
to continue any longer upon such small objects.

"This fatigue our author submitted to for a whole month
together, without any interruption, merely to examine, de-
scribe, and represent the intestines of bees, besides many
months more bestowed upon the other parts ; during which
time he spent whole days in making observations, as long as
there was sufficient light to make any, and whole nights in
registering his observations, till at last he brought his treatise
on bees to the wished-for perfection."

Method of Work. — "For dissecting very minute objects, he
had a brass table made on purpose by that ingenious artist,
Samuel Musschenbroek. To this table were fastened two
brass arms, movable at pleasure to any part of it, and the
up])er portion of these arms was likewise so contrived as to
be susceptible of a very slow vertical motion, by which means
the operator could readily alter their height as he saw most
convenient to his purpose. The ofhce of one of these arms
was to hold the little corpuscles, and that of the other to apply

72 BIOLOGY AND ITS MAKERS

the microscope. His microscopes were of various sizes and
curvatures, his microscopical glasses being of various diam-
eters and focuses, and, from the least to the greatest, the best
that could be procured, in regard to the exactness of the work-
manship and the transparency of the substance.

"But the constructing of very fine scissors, and giving
them an extreme sharpness, seems to have been his chief
secret. These he made use of to cut very minute objects,
because they dissected them equably, whereas knives and
lancets, let them be ever so fine and sharp, are apt to disorder
delicate substances. His knives, lancets, and styles were so
fine that he could not see to sharpen them without the assist-
ance of the microscope; but with them he could dissect the
intestines of bees with the same accuracy and distinctness
that others do those of large animals.

"He was particularly dexterous in the management of
small tubes of glass no thicker than a bristle, drawn to a very
fine point at one end, but thicker at the other."

These were used for inflating hollow structures, and also
for making fine injections. He dissolved the fat of insects
in turpentine and carried on dissections under water.

An unbiased examination of his work will show that it is
of a higher quality than Malpighi's in regard to critical
observation and richness of detail. He also worked with
minuter objects and displayed a greater skill.

The Religious Devotee. — The last part of his life was
dimmed by fanaticism. He read the works of Antoinette
Bourignon and fell under her influence; he began to subdue
his warm and stubborn temper, and to give himself up to
religious contemplation. She taught him to regard scientific
research as worldly, and, following her advice, he gave up his
passionate fondness for studying the works of the Creator,
to devote himself to the love and adoration of that same
Being. Always extreme and intense in everything he under-

INTRODUCTION OF THE MICROSCOPE

13

took, he likewise overdid this, and yielded himself to a sort
of fanatical worship until the end of his life, in 1680. Had
he possessed a more vigorous constitution he would have
been greater as a man. He lived, in all, but forty-three years ;
the last six or seven years were unproductive because of his
mental distractions, and before that, much of his time had
been lost through sickness.

The Biblia Naturae. — It is time to ask, What, with all his
talents and prodigious application, did he leave to science?
This is best answered by an examination of the Biblia Na~
lurcB, under which title all his work was collected. His treatise
on Bees and Mayflies and a few other articles were pub-
lished during his lifetime, but a large part of his observations
remained entirely unknown until they were published in this
book fifty-seven years after his death. In the folio edition
(1737-1738) it embraces 410 pages of text and fifty-three
plates, replete with figures of original observations. It *' con-
tains about a dozen life-histories of insects worked out in more
or less detail. Of these, the mayfly is the most famous, that on
the honey-bee the most elaborate." The greater amount of
his work was in structural entomology. It is known that he
had a collection of about three thousand different species of
insects, which for that period was a very large one. There
is, however, a considerable amount of work on oth er animals ;
the fine anatomy of the snail, the structure of the clam, the
squid; observations on the structure and development of the
frog; observations on the contraction of the muscles, etc., etc.

It is to be remembered that Swammerdam was extremely
exact in all that he did. His descriptions are models of
accuracy and completeness.

Fig. 16 shows reduced sketches of his illustrations of the
structure of the snail. The upper sketch shows the central
nervous system and the nerve trunks connected therev/ith,
and the lower figure shows the shell and the principal muscles.

Fig. i6. — From Swammerdam's Bihlia NaturcB.

INTRODUCTION OF THE MICROSCOPE 75

This is an exceptionally good piece of anatomization for that
time, and is a fair sample of the fidelity with which he worked
out details in the structure of small animals. Besides show-
ing this, these figures also serve the purpose of pointing out
that Swammerdam's fine anatomical work was by no means
confined to insects. His determinations on the structure of
the young frog were equally noteworthy.

But we should have at least one illustration of his handling
of insect anatomy to compare more directly with that of
Malpighi, already given. Fig. 17 is a reduced sketch of the
anatomy of the larva of an ephemerus, showing, besides other
structures, the central nervous system in its natural position.
When compared with the drawings of Malpighi, we see there
is a more masterly hand at the task, and a more critical spirit
back of the hand. The nervous system is very well done,
and the greater detail in other features shows a disposition
to go into the subject more deeply than Malpighi.

Besides working on the structure and life-histories of ani-
mals, Swammerdam showed, experimentally, the irritability
of nerves and the response of muscles after their removal
from the body. He not only illustrates this quite fully, but
seems to have had a pretty good appreciation of the nature
of the problem of the physiologist. He says :

*' It is evident from the foregoing observations that a great
number of things concur in the contraction of the muscles,
and that one should be thoroughly acquainted with that
wonderful machine, our body, and the elements with which
we are surrounded, to describe exactly one single muscle
and explain its action. On this occasion it would be neces-
sary for us to consider the atmosphere, the nature of our food,
the blood, the brain, marrow, and nerves, that most subtle
matter which instantaneously flows to the fibers, and many
other things, before we could expect to attain a sight of the
perfect and certain truth."

Fig. 17. — Anatomy of an Insect: Dissected and Drawn by
Swammerdam.

INTRODUCTION OF THE MICROSCOPE 77

In reference to the formation of animals within the egg,
Swammerdam was, as Malpighi, a believer in the prc-forma-
tion theory. The basis for his position on this question will
be set forth in the chapter on the Rise of Embryology.

There was another question in his time upon which philos-
ophers and scientific men were divided, which was in reference
to the origin of living organisms: Does lifeless matter, some-
times, when submitted to heat and moisture, spring into life ?
Did the rats of Egypt come, as the ancients believed, from
the mud of the Nile, and do frogs and toads have a similar
origin ? Do insects spring from the dew on plants ? etc., etc.
The famous Redi performed his noteworthy experiments
when Swammerdam was twenty-eight years old, but opinion
was divided upon the question as to the possible spontaneous
origin of life, especially among the smaller animals. Upon
this question Swammerdam took a positive stand; he ranged
himself on the side of the more scientific naturalists against
the spontaneous formation of life.

Antony van Leeuwtn'hoek (1632-1723)

In Eeeuwenhoek we find a composed and better-balanced
man. Blessed with a vigorous constitution, he lived ninety-
one years, and worked to the end of his life. He was bom
in 1632, four years after Malpighi, and five before Swammer-
dam; they were, then, strictly speaking, contemporaries.
He stands in contrast with the other men in being self-taught;
he did not have the advantage of a university training, and
apparently never had a master in scientific study. This lack
of systematic training shows in the desultory character of his
extensive observations. Impelled by the same gift of genius
that drove his confreres to study nature with such unexampled
activity, he too followed the path of an independent and
enthusiastic investigator.

78 BIOLOGY AND ITS MAKERS

The portrait (Fig. i8) which forms a frontispiece to his
Arcana Natures represents him at the age of sixty-three,
and shows the pleasing countenance of a firm man in vigor-
ous health. Richardson says: "In the face peering through
the big wig there is the quiet force of Cromwell and the
delicate disdain of Spinoza." "It is a mixed racial type,
Semitic and Teutonic, a Jewish-Saxon; obstinate and yet
imaginative; its very obstinacy a virtue, saving it from flying
too far wild by its imagination."

Recent Additions to His Biography. — There was asingular
scarcity of facts in reference to Leeuwenhoek's life until 1885,
when Dr. Richardson published in TheAsclepiad * the results
of researches made by Mr. A. Wynter Blyth in Leeuwenhoek's
native town of Delft. I am indebted to that article for much
that follows.

His Arcana Natures and other scientific letters contained
a complete record of his scientific activity, but "about his
parentage, his education, and his manner of making a living
there was nothing but conjecture to go upon." The few
scraps of personal history were contained in the PLncyclo-
paedia articles by Carpenter and others, and these were
wrong in sustaining the hypothesis that Teeuwenhoek was
an optician or manufacturer of lenses for the market. Al-
though he ground lenses for his own use, there was no need
on his part of increasing his financial resources by their sale.
He held under the court a minor ofhce designated ' Chamber-
lain of the Sheriff.' The duties of the office were those of a
beadle, and were set forth in his commission, a document
still extant. The requirements were light, as was also the
salary, w^hich amounted to about £26 2i year. He held this
post for thirty-nine years, and the stipend was thereafter
continued to him to the end of his life.

Van Leeuwenhoek was derived from a good Delft family.

* Leeuwenhoek and the Rise of Histology. The Asclepiad, Vol. II, 1885.

Fig. i8. — Leeuwenhoek, 1632-1723.

8o BIOLOGY AND ITS MAKERS

His grandfather and his great-grandfather were Delft brewers,
and his grandmother a brewer's daughter. The family were
doubtless wealthy. His schooling seems to have been brought
to a close at the age of sixteen, when he was '' removed to a
clothing business in Amsterdam, where he filled the office of
bookkeeper and cashier." After a few years he returned to
Delft, and at the age of twenty-two he married, and gave
himself up largely to studies in natural history. Six years
after his marriage he obtained the appointment mentioned
above. He was twice married, but left only one child, a
daughter by his first wife. In the old church at Delft is a
monument erected by this daughter to the memory of her
father.

He led an easy, prosperous, but withal a busy life. The
microscope had recently been invented, and for observation
with that new instrument Leeuwenhoek showed an avidity
amounting to a passion.

''That he was in comfortable, if not affluent, circum-
stances is clear from the character of his writings; that he
was not troubled by any ver}^ anxious and responsible duties
is certain from the continuity of his scientific work; that he
could secure the services of persons of influence is discernible
from the circumstances that, in 1673, De Graaf sent his first
paper to the Royal Society of London; that in 1680 the same
society admitted him as fellow; that the directors of the East
India Company sent him specimens of natural history, and
that, in 1698, Peter the Great paid him a call to inspect his
microscopes and their revelations."

Leeuwenhoek seems to have been fascinated by the mar-
vels of the microscopic world, but the extent and quality of
his work lifted him above the level of the dilettante. He
was not, like Malpighi and Swammerdam, a skilled dissector,
but turned his microscope in all directions; to the mineral
as well as to the vegetable and animal kingdoms. Just when

INTRODUCTION OF THE MICROSCOPE 8l

he began to use the microscope is not known; his first pub-
lication in reference to microscopic objects did not appear
till 1673, when he was forty-one years old.

His Microscopes. — He gave good descriptions and draw-
ings of his instruments, and those still in existence have been
described by Carpenter and others, and in consequence we
have a very good idea of his working equipment. During
his lifetime he sent as a present to the Royal Society of
London twenty-six microscopes, each provided with an object
to examine. Unfortunately, these were removed from the
rooms of the society and lost during the eighteenth century.
His lenses v/ere of fine quality and were ground by himself.
They were nearly all simple lenses, of small size but con-
siderable curvature, and needed to be brought close to the
object examined. He had different microscopes for different
purposes, giving a range of magnifying powers from 40 to 270
diameters and possibly higher. The number of his lenses is
surprising; he possessed not less than 247 complete micro-
scopes, two of which were provided with double lenses, and
one with a triplet. In addition to the above, he had 172
lenses set between plates of metal, which give a total of 419
lenses used by him in his observations. Three were of
quartz, or rock crystal; the rest were of glass. More than
one-half the lenses were mounted in silver; three were in
gold.

It is to be understood that all his microscopes were of
simple construction; no tubes, no mirror; simple pieces
of metal to hold the magnifying-glass and the objects to
be examined, with screws to adjust the position and the
focus.

The three aspects of one of Leeuwenhoek's microscopes

shown in Fig. 19 will give a very good idea of how they were

constructed. These pictures represent the actual size of

the instrument. The photographs were made by Professor

6

82

BIOLOGY AND ITS MAKERS

Nierstrasz from the specimen in possession of the University
of Utrecht. The instrument consists of a double copper plate
in which the circular lens is inserted, and an object-holder — ■
represented in the right-hand lower figure as thrown to one

Fig. 19. — Leeuwenhoek's ^Microscope.
Natural size. From Photographs by Professor Nierstrasz, of Utrecht.

side. By a vertical screw the object could be elevated or
depressed, and by a transverse screw it could be brought
nearer or removed farther from the lens, and thus be brought
into focus.

Fig. 20a shows the way in which the microscope was

INTRODUCTION OF THE MICROSCOPE

83

arranged to examine the circulation of blood in the trans-
parent tail of a small fish. The fish was 'placed in
water in a slender glass tube, and the latter was held in a
metallic frame, to which a
plate (marked D) was joined,
carrying the magnifying
glass. The latter is indi-
cated in the circle above the
letter D, near the tail- fin of
the fish. The eye was ap-
plied close to this circular
magnifying-glass, which was
brought into position and
adjusted by means of screws.
In some instances, he had a
concave reflector with a hole
in the center, in which his
magnifying-glass was insert-
ed; in this form of instru-
ment the objects were illu-
mined by reflected, and not
by transmitted light.

His Scientific Letters. —
His microscopic observations
were described and sent to
learned societies in the form
of letters. " All or nearly all
that he did in a literary way
was after the manner of an
epistle," and his written com-
munications were so numer-
ous as to justify the cogno-
men, "The man of many ,, Fjg. 20a. — Leeuwenhoek's
1 ^. n urr-i T- 1 A 1 Mechanism for Examining the
letters." '' The French x\cad- Circulation of the Blood.

84

BIOLOGY AND ITS MAKERS

emy of Sciences, of which he was elected a corresponding
member in 1697, got twenty-seven; but the lion's share
fell to the young Royal Society of London, which in fifty
years — 1673-1723 — received 375 letters and papers." " The
works themselves, except that they lie in the domain of
natural history, are disconnected and appear in no order
of systematized study. The philosopher was led by what
transpired at any moment to lead him."

The Capillary Circulation. — In 1686 he obscr^'ed the
minute circulation of the blood, and demonstrated the capil-
lary connection between arteries and veins, thus forging the

final link in the chain of

/^- r-

observation showing the
relation between these
blood-vessels. This was
perhaps his most important
observation for its bearing
on physiology. It must be
remembered that Harvey
had not actually seen the
circulation of the blood,
which he announced in
1628. He assumed on en-
tirely sufficient grounds the
existence of a complete cir-
culation, but there was
wanting in his scheme the
direct ocular proof of the
passage of blood from arteries to veins. This was supplied
by Leeuwenhoek. Fig. 2oh shows one of his sketches of the
capillary circulation. In his efforts to see the circulation
he tried various animals; the comb of the young cock, the
ears of white rabbits, the membraneous wing of the bat w^ere
progressively examined. The next advance came when he

Fig. 206. — The Capillary Circula-
tion. (After Leeuwenhoek.)

INTRODUCTION OF THE MICROSCOPE 85

directed his microscope to the tail of the tadpole. Upon
examining this he exclaims:

" A sight presented itself more delightful than any mine
eyes had ever beheld ; for here I discovered more than fifty
circulations of the blood in different places, while the animal
lay quiet in the water, and I could bring it before my micro-
scope to my wish. For I saw not only that in many places
the blood was conveyed through exceedingly minute vessels,
from the middle of the tail tovx-ard the edges, but that each
of the vessels had a curve or turning, and carried the blood
back toward the middle of the tail, in order to be again con-
veyed to the heart. Hereby it plainly appeared to me that
the blood-vessels which I now savv^ in the animal, and w^hich
bear the names of arteries and veins are, in fact, one and the
same; that is to say, that they are properly termed arteries
so long as they convey the blood to the f urtherest extremities
of its vessels, and veins Vv'hen they bring it back to the heart.
And thus it appears that an SLvtery and a vein are one and
the same vessel prolonged or extended."

This description shows that he fully appreciated the course
of the minute vascular circulation and the nature of the
communication between arteries and veins. He afterward
extended his observations to the web of the frog's foot, the
tail of young fishes and eels.

In connection with this it should be remembered that
Malpighi, in 1661, observ^ed the flow of blood in the lungs
and in the mesentery of the frog, but he made little of the
discovery. Leeuwenhoek did more with his, and gave the
first clear idea of the capillary circulation. Leeuwenhoek
was anticipated also by Malpighi in reference to the micro-
scopic structure of the blood. (See also under Swammer-
dam.) To Malpighi the corpuscles appeared to be globules
of fat, while Leeuwenhoek noted that the blood disks of
birds, frogs, and fishes were oval in outline, and those of

86

BIOLOGY AND ITS MAKERS

mammals circular. He reserved the term ' globule ' for
those of the human body, erroneously believing them to
be spheroidal.

Other Discoveries. — Among his other discoveries bear-
ing on physiology and medicine may be mentioned: the
branched character of heart muscles, the stripe in voluntary
muscles, the structure of the crystalline lens, the description
of spermatozoa after they had been pointed out to him in
1674 by Hamen, a medical student in Leyden, etc. Richard-
son dignified him with the title 'the founder of histology,'
but this, in view of the work of his great contemporary,
Malpighi, seems to me an overestimate.

Turning his microscope in all directions, he examined
water and found it peopled with minute animalcules, those
simple forms of animal life propelled through the water by
innumerable hair-like cilia extending from the body like
banks of oars from a galley, except that in
many cases they extend from all surfaces.
He saw- not only the animalcules, but also
the cilia that m.ove their bodies.

He also discovered the Rotifers, those

favorites of the amateur microscopists, made

so familiar to the general public in works

like Gosse's Evenings at the Microscope.

He observed that when water containing

these animalcules

evaporated they were

reduced to fine dust,

but became alive

again, after great

lapses of time, by the

introduction of water.

Fig. 2 1. —Plant Cells. (From Leeuwen- ^^ ^^^^ ^^^y

hoek's Arcana Natures.) observations on the

INTRODUCTION OF THE MICROSCOPE 87

microscopic structure of plants. Fig. 21 gives a fair sample
of the extent to which he observed the cellular construction
of vegetables and anticipated the cell theory. While Mal-
pighi's research in that field was more extensive, these
sketches from Lceuwenhoek represent very well the char-
acter of the work of the period on the minute structures
of plants.

His Theoretical Views. — It remains to say that on the
two biological questions of the day he took a decisive stand.
He was a believer in pre-formation or pre-delineation of the
embr}'0 in an extreme degree, seeing in fancy the complete
outline of both maternal and paternal individuals in the
spermatozoa, and going so far as to make sketches of the
same. But on the question of the spontaneous origin of life
he took the side that has been supported with such triumphant
demonstration in this century ; namely, the side opposing the
theory of the occurrence of spontaneous generation under
present conditions of life.

Comparison of the Three Men. — ^We see in these
three gifted contemporaries different personal characteristics.
I.eeuwenhoek, the composed and strong, attaining an age
of ninety-one; Malpighi, always in feeble health, but direct-
ing his energies with rare capacity, reaching the age of sixty-
seven ; while the great intensity of Swammerdam stopped his
scientific career at thirty-six and burned out his life at the
age of forty-three.

They were all original and accurate observers, but there
is variation in the kind and quality of their intellectual prod-
uct. The two university-trained men showed capacity for
coherent observation; they were both better able to direct
their efforts toward some definite end; LeeuAvenhoek, with
the advantages of vigorous health and long working period,
lacked the systematic training ot the schools, and all his life
wrought in discursive fashion; he left no coherent piece of

88 BIOLOGY AND ITS MAKERS

work of any extent like Malpighi's Anatome Planiarum or
Swammerdam's Anatomy and Metamorphosis of Insects.

Swammerdam was the most critical observer of the three,
if we may judge by his labors in the same field as Malpighi's
on the silkworm. His descriptions are models of accuracy
and completeness, and his anatomical work shows a higher
grade of finish and completeness than Malpighi's. Malpighi,
it seems to me, did more in the sum total than either of the
others to advance the sciences of anatomy and physiology,
and through them the interests of mankind. Leeuwenhoek
had larger opportunity; he devoted himself to microscopic
observations, but he w^andered over the whole field. While
his observations lose all monographic character, nevertheless
they were important in opening new fields and advancing the
sciences of anatomy, physiology, botany, and zoology.

The combined force of their labors marks an epoch
characterized by the acceptance of the scientific method and
the establishment of a new grade of intellectual life. Th rough
their efforts and that of their contemporaries of lesser note
the new intellectual movement was now well under way.

CHAPTER V

THE PROGRESS OF MINUTE ANATOMY.

The work of Malpighi, Swammerdam, and Leeuwenhoek
stimulated investigations into the structure of minute an-
imals, and researches in that field became a feature of the
advance in the next century. Considerable progress was
made in the province of minute anatomy before comparative
anatomy grew into an independent subject.

The attractiveness of observations upon the life-histories
and the structure of insects, as shown particularly in the pub-
lications of Malpighi and Swammerdam, made those animals
the favorite objects of study. The observers were not long
in recognizing that some of the greatest beauties of organic
architecture are displayed in the internal structure of
insects. The delicate tracery of the organs, their minuteness
and perfection are w^ell calculated to awaken surprise. Well
might those early anatomists be moved to enthusiasm over
their researches. Every excursion into this domain gave
only beautiful pictures of a mechanism of exquisite delicacy,
and their wonder grew into amazement. Here began a new
train of ideas, in the unexpected revelation that within the
small compass of the body of an insect w^as embraced such
a complex set of organs; a complete nervous system, fine
breathing-tubes, organs of circulation, of digestion, etc., etc.

Lyonet. — The first piece of structural work after Swam-
merdam's to which we must give attention is that of Lyonet,
who produced in the middle of the eighteenth century one of

89

90

BIOLOGY AND ITS MAKERS

the most noteworthy monographs in the field of minute
anatomy. This was a work like that of Malpighi, upon the
anatomy of a single form, but it was carried out in much

Fig. 22. — Lyonet, 1707-1789.

greater detail. The 137 figures on the 18 plates are models
of close observation and fine execution of drawings.

Lyonet (also written Lyonnet) was a Hollander, born in
The Hague in 1707. He was a man of varied talents, a
painter, a sculptor, an engraver, and a very gifted linguist.

PROGRESS OF MINUTE ANATOMY 9^

It is said that he was skilled in at least eight languages; and
at one time he was the cipher secretary and confidential
translator for the United Provinces of Holland. He was
educated as a lawyer, but, from interest in the subject, de-
voted most of his time to engraving objects of natural history.
Among his earliest published drawings were the figures for
Cesser's Theology oj Insects (1742) and for Trembley's
famous treatise on Hydra (1744).

His Great Monograph. — Finally I>yonet decided to branch
out for himself, and produce a monograph on insect anatomy.
After some preliminary work on the sheep-tick, he settled
upon the caterpillar of the goat moth, which lives upon the
willow-tree. His work, first published in 175c, bore the title
Traite Anatomique de la Chenille qui ronge le hois de Saule.
In exploring the anatomy of the form chosen, he displayed
not only patience, but great skill as a dissector, while his
superiority as a draughtsman was continually shown in his
sketches. He engraved his own figures on copper. The draw-
ings are very remarkable for the amount of detail that they
show. He dissected this form with the same thoroughness
with which medical men have dissected the human body.
The superficial nmscles were carefully drawn and were then
cut away in order to expose the next underlying layer which,
in turn, v/as sketched and then removed. The amount of
detail involved in this work may be in part realized from the
circumstance that he distinguished 4,041 separate muscles.
His sketches show these muscles accurately drawn, and the
principal ones are lettered. When he came to expose the
nerves, he followed the minute branches to individual small
muscles and sketched them, not in a diagrammatic way, but
as accurate drawings from the natural object. The breath-
ing-tubes were followed in the same manner, and the other
organs of the body were all dissected and drawn with remark-
able thoroughness. Lyonet was not trained in anatomy

92

BIOLOGY AND ITS MAKERS

like Malpighi and Swammerdam, but being a man of unusual
patience and manual dexterity, he accomplished notable
results. His great quarto volume is, however, mxrely a de-
scription of the figures, and lacks the insight of a trained
anatomist. His skill as a dissector
is far ahead of his knowledge of
anatomy, and he becomes lost in
the details of his subject.

Extraordinary Quality of the
Drawings. — ^A few figures will serve
to illustrate the character of his
work, but the reduced reproduc-
tions which follow can not do justice
to the copper plates of the original.
Fig. 23 gives a view of the exter-
nal appearance of the caterpillar
which was dissected. When the
skin was removed from the outside
the muscles came into view, as
shown in Fig. 24. This is a view
from the ventral side of the animal.
On the left side the more super-
ficial muscles show, and on the
right the next deeper layer.

Fig. 25 shows his dissection of
the nerves. In this figure the mus-
cles are indicated in outline, and
the distribution of nerves to partic-
ular muscles is shown.

Lyonet's dissection of the head
is an extraordinary feat. The en-
tire head is not more than a quarter of an inch in diam-
eter, but in a series of seven dissections he shows all of the
internal organs in the head. Fig. 26 shows two sketches

1

1 ■'4.>

1

1

1

Fig. 23. — Larva of the
Willow Moth. (From
Lyonet's Monograph,
1750)

'-7:'i^' 'I

Fig. 24.

Fig. 25.

Fig. 24.— Muscles of the Larva of the Willow Moth. (From
Lyonet's Monograph.)

YiG, 25.— Central Nervous System and Nerves of the Same.

94

BIOLOGY AND ITS MAKERS

exhibiting the nervous gangha, the air tubes, and muscles of
the head in their natural position.

Fig. 27 shows the nervous system of the head, including
the extremely fine nervous masses which are designated the
sympathetic nervous system.

The extraordinary character of the drawings in Lyonet's
monograph created a sensation. The existence of such com-
plicated structures within the body of an insect was dis-

FiG. 26. — Dissection of the Head of the Larva of the Willow Moth.

credited, and, furthermore, some of his critics declared that
even if such a fine organization existed, it would be beyond
human possibilities to expose the details as shown in his
sketches. Accordingly, Lyonet was accused of drawing on
his imagination. In order to silence his critics he published
in the second edition of his work, in 1752, drawings of his
instruments and a description of his methods.

Lyonet intended to work out the anatomy of the chrysalis
and the adult form of the same animal. In pursuance of

PROGRESS OF MINUTE ANATOMY

9S

this plan, he made many dissections and drawings, but, at
the age of sixty, on account of the condition of his eyes, he-
was obliged to stop all close work, and his project remained
unfinished. The sketches which he had accumulated were
published later, but they fall far short of those illustrating

1 W: .

mm

1

ii'iG. 27. — The Brain and Head Nerves of the Same Animal.

the Traite Anatomique. Lyonet died in 1789, at the age of
eighty-one.

Roesel, Reaumur, and De Geer on Insect Life. — ^\Ve must
also take note of the fact that, running parallel with this work
on the anatomy of insects, observations and publications had
gone forward on form, habits, and metamorphosis of insects,
that did more to advance the knowledge of insect life than

0 BIOLOGY AND ITS MAKERS

Lyonet's researches. Roesel, in Germany, Reaumur, in
France, and De Geer, in Sweden, were all distinguished ob-
servers in this line. Their works are voluminous and are
well illustrated. Those of Reaumur and De Geer took the
current French title of Memoires pour servir a VHistoire des
Insectes. The plates with which the collected publications
of each of the three men are provided show many sketches
of external form and details of external anatomy, but very
few illustrations of internal anatomy occur. The sketches
of Roesel in particular are worthy of examination at the pres-
ent time. Some of his masterly figures in color are fine
examples of the art of painting in miniature. The name of
Roesel (Fig. 28) is connected also with the earliest observa-
tions of protoplasm and with a notable publication on the
Batrachians.

Reaumur (Fig. 29), who was distinguished for kindly
and amiable personal qualities, was also an important man
in his influence upon the progress of science. He was both
physician and naturalist; he made experiments upon the
physiology of digestion, which aided in the understanding of
that process; he invented the thermometer which bears his
name, and did other services for the advancement of sci-
ence.

Straus-Durckheim's Monograph on Insect Anatomy. —
Insect anatomy continued to attract a number of observers,
but we must go forward into the nineteenth century before
we find the subject taking a new direction and merging into
its modem phase. The remarkable monograph of Straus-
Durckheim represents the next step in the development of
insect anatomy toward the position that it occupies to-day.
His aim is clearly indicated in the opening sentence of his
preface: "Having been for a long time occupied with the
study of articulated animals, I propose to publish a general
work upon the comparative anatomy of that branch of the

\i:(;i\ST lOHAKN

tjr^f^'A ^iurti 4.vi yLrz rji

M.alilen

Fig. 28. — RoESEL von Rosenhof, 1705-1759-

98

BIOLOGY AND ITS MAKERS

animal kingdom." He was working under the influence of
Cuvier, who, some years earlier, had founded the science of
comparative anatomy and whom he recognized as his great
exemplar. His work is dedicated to Cuvier, and is accom-

IG 29.

-Reaumur, 1683-1757.

panied by a letter to that great anatomist expressing his
thanks for encouragement and assistance.

Straus-Diirckheim (i 790-1865) intended that the general
considerations should be the chief feature of his monograph,
but they failed in this particular because, with the further
developments in anatomy, including embryology and the
cell-theory, his general discussions regarding the articulated

PROGRESS OF MINUTE ANATOMY 99

animals became obsolete. The chief value of his work now
lies in what he considered its secondary feature, viz., that of
the detailed anatomy of the cockchafer, one of the common
beetles of Europe. Owing to changed conditions, therefore,
it takes rank with the work of Malpighi and Lyonet, as a
monograph on a single form. Originally he had intended
to publish a series of monographs on the structure of insects
typical of the different families, but that upon the cockchafer
was the only one completed.

Comparison with the Sketches of Lyonet. — The quality
of this work upon the anatomy of the cockchafer was excel-
lent, and in 1824 it was accepted and crowned by the Royal
Institute of France. The finely lithographed plates were
prepared at the expense of the Institute, and the book was
published in 1828 with the following cumbersome title: Con-
sider alions Generales stir PAnatomie com par ee des Animaux
Articules auxquelles on a joint VAnatomie Descriptive du
Melolontha Vulgaris (Hanneton) donnee comme example de
r Organisation des C ol copter es. The 109 sketches with which
the plates are adorned are very beautiful, but one who com-
pares his drawings, figure by figure, with those of Lyonet
can not fail to see that those of the latter are more detailed
and represent a more careful dissection. One illustration
from Straus-Diirckheim will suffice to bring the achievements
of the two men into comparison.

Fig. 30 shows his sketch of the anatomy of the central
nervous system. He undertakes to show only the main
branches of the nerves going to the different segments of the
body, while Lyonet brings to view the distribution of the
minute terminals to particular muscles. Comparison of other
figures — notably that of the dissection of the head— will
bring out the same point, viz., that Lyonet was more detailed
than Straus-Diirckheim in his explorations of the anatomy of
insects, and fully as accurate in drawing what he had seen.

lOO BIOLOGY AND ITS MAKERS

Nevertheless, the work of Straus-Durckheim is conceived
in a different spirit, and is the first serious attempt to make
insect anatomy broadly comparative.

Comment. — Such researches as those of Swammerdam,
Lyonet, and Straus-Durckheim represent a phase in the
progress of the study of nature. Perhaps their chief value
lies in the fact that they embody the idea of critical observa-
tion. As examples of faithful, accurate observations the re-
searches helped to bring about that close study which is our
only means of getting at basal facts. These men were all
enlisted in the crusade against superficial observation. This
had to have its beginning, and v/hen we witness it in its early
stages, before the researches have become illuminated by great
ideas, the prodigious effort involved in the detailed researches
may seem to be poorly expended labor. Nevertheless, though
the writings of these pioneers have become obsolete, their
work was of importance in helping to lift observations upon
nature to a higher level.

Dufour. — Leon Dufour extended the work of Straus-
Diirckheim by publishing, between 1831 and 1834, researches
upon the anatomy and physiology of different families of
insects. His aim was to found a general science of insect
anatomy. That he was unsuccessful in accomplishing this
was owing partly to the absence of embryology and histology
from his method of study.

Newport. — The thing most needed now was not greater
devotion to details and a willingness to work, but a broaden-
ing of the horizon of ideas. This arrived in the Englisliman
Newport, who was remarkable not only for his skill as a
dissector, but for his recognition of the importance of embry-
ology in elucidating the problems of structure. His article
"Insecta" in Todd's Cyclopcedia of Anatomy and Physiol-
ogy^ in 1 84 1, and his papers in the Philosophical Transac-
tions of the Royal Society contain tliis new kind of research.

Fig. 30. — Nervous System of the Cockchafer. (From Straus-
Diirckheim's Monograph, 1828.)

102 BIOLOGY AND ITS MAKERS

Von Baer had founded embryology by his great work on the
development of animals in 1828, before the investigations of
Dufour, but it was reserved for Newport to recognize its
great importance and to apply it to insect anatomy. He saw
clearly that, in order to comprehend his problems, the anat-
omist must take into account the process of building the body,
as well as the completed architecture of the adult. The in-
troduction of this important idea made his achievement a
distinct advance beyond that of his predecessors.

Leydig. — Just as Newport was publishing his conclusions
the cell-theory was established (in 1838-39); and this was
destined to furnish the basis for a new advance. The in-
fluence of the doctrine that all tissues are composed of similar
vital units, called cells, was far-reaching. Investigators began
to apply the idea in all directions, and there resulted a new
department of anatomy, called histology. The subject of
insect histology was an unworked field, but manifestly one
of importance. Franz Leydig (for portrait see p. 175)
entered the new territory with enthusiasm, and through his
extensive investigations all structural studies upon insects
assumed a nev/ aspect. In 1864 appeared his Vom Bau des
Thierchen Korpers, which, together with his special articles,
created a new kind of insect anatomy based upon the micro-
scopic study of tissues. The application of this method of
investigation is easy to see; just as it is impossible to under-
stand the working of a machine without a knowledge of its
construction, so a knowledge of the working units of an organ
is necessary to comprehend its action. For illustration, it is
perfectly evident that we can not understand what is taking
place in an organ for receiving sensory impressions without
first understanding its mechanism and the nature of the
connections between it and the central part of the nervous
system. The sensory organ is on the surface in order more
readily to receive impressions from the outside world. The

PROGRESS OF MINUTE ANATOMY 103

sensory cells are also modifications of surface cells, and, as
a preliminary step to understanding their particular office,
we must know the line along which they have become modi-
fied to fit them to receive stimulation.

Then, if we attempt to follow in the imagination the way
by which the surface stimulations reach the central nervous
system and affect it, we must investigate all the connections.
It thus appears that we must know the intimate structure of
an organ in order to understand its physiology. Leydig
supplied this kind of information for many organs of insects.
In his investigations we see the foundation of that delicate
work upon the microscopic structure of insects which is still
going forward.

Summary. — In this brief sketch we have seen that the
study of insect anatomy, beginning with that of Malpighi
and Swammerdam, was lifted to a plane of greater exactitude
by Lyonet and Straus-Diirckheim. It was further broadened
by the researches of Dufour, and began to take on its modem
aspects, first, through the labors of Newport, who introduced
embryology as a feature of investigation, and, finally, through
Leydig's step in introducing histology. In the combination
of the work of these two observers, the subject for the first
time reached its proper position.

The studies of minute structure in the seventeenth and
eighteenth centuries were by no means confined to insects;
investigations were made upon a number of other forms.
Trembley, in the time of Lyonet, produced his noteworthy
memoirs upon the small fresh-water hydra (Memoires pour
servir a Vhistoire des polypes d'eau douce, 1744); the illustra-
tions for which, as already stated, were prepared by Lyonet.
The structure of snails and other mollusks, of tadpoles, frogs,
and other batrachia, was also investigated. We have seen
that Swammerdam, in the seventeenth century, had begun
observations upon the anatomy of tadpoles, frogs, and snails,

I04 BIOLOGY AND ITS MAKERS

and also upon the minute Crustacea commonly called water-
fleas, which are just large enough to be distinguished by the
unaided eye. We should remember also that in the same
period the microscopic structure of plants began to be inves-
tigated, notably by Grew, Malpighi, and Leeuwenhoek (see
Chapter IV).

In addition to those essays into minute anatomy, in which
scalpel and scissors were employed, an endeavor of more
subtle difficulty made its appeal ; there were forms of animal
life of still smaller size and simpler organization that began
to engage the attention of microscopists. A brief account of
the discovery and subsequent observation of these micro-
scopic animalcula will now occupy our attention.

The Discovery of the Simplest Animals and the Prog-
ress OF Observations upon Them

These single-celled animals, since 1845 called protozoa,,
have become of unusual interest to biologists, because in them
the processes of life are reduced to their sim.pl est expression.
The vital activities taking place in the bodies of higher animals,
are too complicated and too intricately mixed to admit of
clear analysis, and, long ago, physiologists learned that the
quest for explanations of living activities lay along the line
of investigating them in their most rudimentary expression.
The practical recognition of this is seen in our recent text-
books upon human physiology, which commonly begin with
discussions of the life of these simplest organisms. That
greatest of all text-books on general physiology, written by
Max Verworn, is devoted largely to experimental studies
upon these simple organisms as containing the key to the
similar activities (carried on in a higher degree) in higher
animals. This group of animals is so important as a field
of experimental observation that a brief account of their

DISCOVERY OF THE PROTOZOA 105

discovery and the progress of knowledge in reference to them
will be in place in this chapter.

Discovery of the Protozoa. — Leeuw^enhoek left so little
unnoticed in the microscopic world that we are prepared to
find that he made the first recorded observations upon these
animalcula. His earliest observations were communicated
by letter to the Royal Society of London, and were published
in their Transactions in 167 7. It is very interesting to read
his descriptions expressed in the archaic language of the time.
The following quotation from a Dutcli letter turned into
English will suffice to give the flavor of his writing:

"In the year 1675 I discovered living creatures in rain-
water which had stood but four days in a new earthen pot,
glazed blew within. This invited me to view the water with
great attention, especially those little animals appearing to
me ten thousand times less than those represented by Mons.
Swammerdam, and by him called water-fleas or water-lice,
which may be perceived in the water with the naked eye.
The first sorte by me discovered in the said water, I divers
times observ^ed to consist of five, six, seven or eight clear
globules, without being able to discover any film that held
them together or contained them. When these animalcula,
or living atoms, did move they put forth two little horns,
continually moving themselves; the place between these
two horns was flat, though the rest of the body was roundish,
sharpening a little towards the end, where they had a tayle,
near four times the length of the whole body, of the thick-
ness (by my microscope) of a spider's web; at the end of
which appeared a globule, of the bigness of one of those
which made up the body; which tayle I could not perceive
even in very clear water to be mov'd by them. These little
creatures, if they chanced to light upon the least filament
or string, or other such particle, of which there are many in
the water, especially after it has stood some days, they stook

I06 BIOLOGY AND ITS MAKERS

entangled therein, extending their body in a long round, and
striving to dis-entangle their tayle; whereby it came to pass,
that their whole body lept back towards the globule of the
tayle, which then rolled together serpent-like, and after the
manner of copper or iron wire, that having been wound
around a stick, and unwound again, retains those v/indings
and turnings," etc.*

x\ny one who has examined under the microscope the well-
known bell -animalcule will recognize in this first description
of it, the stalk, and its form after contraction under the desig-
nation of a ' tayle which retains those windings and turnings.'

There are many other descriptions, but the one given is
typical of the others. He found the little animals in water,
in infusions of pepper, and other vegetable substances, and
on that account they came soon to be designated infusoria.
His observations were not at first accompanied by sketches,
but in 1 71 1 he sent some drawings with further descriptions.

O. Fr. Mtiller. — These animalcula became favorite ob-
jects of microscopic study. Descriptions began to accu-
mulate and drawings to be made until it became evident that
there were many different kinds. It was, however, more
than one hundred years after their discovery by Leeuwenhoek
that the first standard work devoted exclusively to these
animalcula was published. This treatise by O. Fr. Miiller
was published in 1786 under the title of Animalctda Infusoria,
The circumstance that this volume of quarto size had 367
pages of description with 50 plates of sketches will gi^'e some
indication of the number of protozoa known at that time.

Ehrenberg. — Observations in this domain kept accu-
mulating, but the next publication necessary to mention is that
of Ehrenberg (i 795-1876). This scientific traveler and
eminent observer was the author of several works. He was

* Kent's Manual of the Infusoria, Vol. I, p. 3. Quotation from the
Philosophical Transactions for the year 1677.

DISCOVERY OF THE PROTOZOA 1^7

one of the early observers of nerve fibres and of many other
structures of the animal frame. His book of the protozoa
is a beautifully illustrated monograph consisting of 532 pages
of letterpress and 69 plates of folio size. It was published in
1836 under the German title of Die Injusionsthierchen als
Vollkommene Or ganismen, or ''The Infusoria as Perfect Or-
ganisms." The animalcula which he so faithfully represented
in his sketches have the habit, when feeding, of taking into
the body collections of food -particles, aggregated into spher-
ical globules or food vacuoles. These are distinctly sepa-
rated, and slowly circulate around the single-celled body while
they are undergoing digestion. In a fully fed animal these
food-vacuoles occupy different positions, and are enclosed in
globular spaces in the protoplasm, an adjustment that gave
Ehrenberg the notion that the animals possessed many
stomachs. Accordingly he gave to them the name '' Poly-
gastrica," and assigned to them a much higher grade of
organization than they really possess. These conclusions,
based on the general arrangement of food globules, seem
very curious to us to-day. His publication was almost simul-
taneous with the announcement of the cell-theory (1838-39),
the acceptance of which was destined to overthrow his con-
ception of the protozoa, and to make it clear that tissues and
organs can belong only to multicellular organisms.

Ehrenberg (Fig. 31) was a man of great scientific attain-
ments, and notwithstanding the grotesqueness of some of his
conclusions, was held in high esteem as a scientific investi-
gator. His observations were accurate, and the beautiful
figures vvith which his work on the protozoa is embellished
were executed with such fidelity regarding fine points of
microscopic detail that they are of value to-day.

Dujardin, whom we shall soon come to know as the dis-
coverer of protoplasm, successfully combated the concUisions
of Ehrenberg regarding the organization of the protozoa.

io8

BIOLOGY AND ITS MAKERS

For a time the great German scientist tried to maintain his
point, that the infusoria have many stomachs, but this was
completely swept away, and finally the contention of Von
Siebold was adopted to the effect that these animals are each
composed of a single cell.

In 1845 Stein, whose influence was greater than that of
Ehrenberg, is engrossed in proposing names for the suborders

Fig. 31. — Ehrenberg, 1795-1876.

of infusoria based upon the distribution of cilia upon their
bodies. This simple method of classification, as well as the
names introduced by Stein, is still in use.

Since Stein there have been many workers on protozoa,
but the researches of Richard Hertwig, Biitschli, Doeflein,
and Fritz Schaudinn are of especial importance, and with the

DISCOVERY OF THE PROTOZOA 109

contributions of these and other observers we enter the
modern epoch.

The importance of these animals in affording a field for
experimentation on the simplest expressions of life has al-
ready been indicated. Many interesting problems have
arisen in connection with recent studies of them and, as a
consequence, a separate division of biological study desig-
nated protozoology is recognized. The group embraces the
very simplest manifestations of animal Hfe, and the experi-
ments upon the different forms light the way for studies
of the vital activities of the higher animals. Some of the
protozoa are disease producing; as the microbe of malaria,
of the sleeping sickness, etc., while, as is well known, most
diseases that have been traced to specific germs are caused
by plants — the bacteria. Many experiments of Maupas,
Calkins and others have a bearing upon the discussions
regarding the immortality of the protozoa, an idea which
was at one time a feature of Weissmann's theory of heredity.
Binet and others have discussed the evidences of psychic
life in these micro-organisms, and the daily activity of a
protozoan became the field for observation and record in
an American laboratory of psychology. The extensive stud-
ies of Jennings on the nature of their responses to stim-
ulations form a basis for some of the discussions on animal
behavior.

CHAPTER VI

LINN^US AND SCIENTIFIC NATURAL HISTORY

We turn now from the purely anatomical side to consider
the parallel development of the classification of animals and
of plants. Descriptive natural history reached a very low
level in the early Christian centuries, and remained there
throughout the Middle Ages. The return to the writings of
Aristotle was the first influence tending to lift it to the position
from which it had fallen. After the decline of ancient civili-
zation there was a period in which the writers of classical
antiquity were not read. Not only were the v/ritings of the
ancient philosophers neglected, but so also were those of the
literary men as well, the poets, the story-tellers, and the his-
torians. As related in Chapter I, there were no observations
of animated nature, and the growing tendency of the educated
classes to envelop themselves in metaphysical speculations
was a feature of intellectual life.

The Physiologus or Sacred Natural History. — During this
period of crude fancy, with a fog of mysticism obscuring all
phenomena of nature, there existed a peculiar kind of natural
history that was produced under theological influence. The
manuscripts in which this sacred natural history v/as em-
bodied exist in various forms and in about a dozen languages
of Eastern and Western Europe. The writings are known
under the general title of the Physiologus, or the Bestiarius.
This served for nearly a thousand years as the principal
source of thought regarding natural history. It contains

no

LINN^US AND NATURAL HISTORY m

accounts of animals mentioned in the Bible and others of a
purely mythical character. These are made to be symbolical
of religious beliefs, and are often accompanied by quotations
of texts and by moral reflections. The phoenix rising from
its ashes typifies the resurrection of Christ. In reference to
young lions, the Physiologus says: "The lioness giveth birth
to cubs which remain three days without life. Then cometh
the lion, breath eth upon them, and bringeth them to life. . . .
Thus it is that Jesus Christ during three days was deprived
of life, but God the Father raised him gloriously." (Quoted
from White, p. 35.) Besides forty or fifty common animals,
the unicorn and the dragon of the Scriptures, and the fabled
basilisk and phoenix of secular writings are described, and
morals are drawn from the stories about them. Some of the
accounts of animals, as the lion, the panther, the serpent, the
weasel, etc., etc., are so curious that, if space permitted, it
would be interesting to quote them; but that would keep us
too long from following the rise of scientific natural history
from this basis.

For a long time the religious character of the contempla-
tions of nature was emphasized and the prevalence of theo-
logical influence in natural history is shown in various titles,
as Lesser's Theology oj Insects, Swammerdam's Bihlia
NaturcB, Spallanzani's Tracts, etc.

The zoology of the Physiologus w^as of a much lower grade
than any we know about among the ancients, and it is a
curious fact that progress was made by returning to the
natural history of fifteen centuries in the past. The transla-
tion of Aristotle's writings upon animals, and the disposition
to read them, mark this advance. When, in the Middle
Ages, the boundaries of interest began to be extended, it
came like an entirely new discovery, to find in the writings
of the ancients a storehouse of philosophic thought and a
higher grade of learning than that of the period. The

112 BIOLOGY AND ITS MAKERS

translation and recopying of the writers of classical antiquity
was, therefore, an important step in the revival of learning.
These writings were so much above the thought of the time
that the belief was naturally created that the ancients had
digested all learning, and they were pointed to as unfailing
authorities in matters of science.

The Return to the Science of the Ancients. — The return to
Aristotle was wholesome, and under its influence men turned
their attention once more to real animals. Comments upon
Aristotle began to be made, and in course of time independent
treatises upon animals began to appear. One of the first to
modify Aristotle to any purpose was Edward Wotton, the
English physician, who published in 1552 a book on the dis-
tinguishing characteristics of animals {De Differ entiis Ani-
malium). This was a complete treatise on the zoology of
the period, including an account of the different races of
mankind. It was beautifully printed in Paris, and was
dedicated to Edward VI. Although embracing ten books,
it was by no means so ponderous as were som.e of the treatises
that followed it. The work was based upon Aristotle, but
the author introduced new matter, and also added the group
of zoophytes, or plant-like animals of the sea.

Gesner. — The next to reach a distinctly higher plane was
Conrad Gesner (i 516-1 565), the Swiss, who was a contem-
porary of Vesalius. He was a practising physician who, in
1553, was made professor of natural history in Zurich. A
man of extraordinary talent and learning, he turned out an
astonishing quantity of work. Besides accomplishing much
in scientific lines, he translated from Greek, Arabic, and
Hebrew, and published in twenty volumes a universal cat-
alogue of all works known in Latin, Greek, and Hebrew,
either printed or in manuscript form. In the domain of
natural history be began to look critically at animals with a
view to describing them, and to collect with zealous care new

LINN^US AND NATURAL HISTORY 113

observations upon their habits. His great work on natural
history (Historia Animalium) began to appear in 1551, when
he was thirty-five years of age, and four of the five volumes
were published by 1556. The fifth volume was not pub-
lished until 1587, tv/enty-two years after his death. The
complete work consists of about " 4,500 folio pages," profusely
illustrated with good figures. The edition which the writer
has before him — that of 1 585-1604 — embraces 3,200 pages
of text and 953 figures.

Brooks says: "One of Gesner's greatest serv^ices to nat-
ural science is the introduction of good illustrations, which he
gives his reader by hundreds." He was so exacting about
the quality of his illustrations that his critical supervision of
the work of artists and engravers had its influence upon con-
temporary art. Some of the best woodcuts of the period are
found in his work. Albrecht Diirer supplied one of the
originals — the drawing of the rhinoceros — and it is interest-
ing to note that it is by no means the best, a circumstance
which indicates how effectively Gesner held his engravers
and draughtsmen up to fine work. He was also careful
to mold his writing into graceful form, and this, combined
with the illustrations, " made science attractive without sac-
rificing its dignity, and thus became a great educational
influence."

In preparing his work he sifted the writings of about two
hundred and fifty authors, and while his book is largely a
compilation, it is enriched with many observations of his own.
His descriptions are verbose, but discriminating in separating
facts and observations from fables and speculations. He
could not entirely escape from old traditions. There are re-
tained in his book pictures of the sea-serpent, the mermeids,
and a few other fanciful and grotesque sketches, but for the
most part the drawings are made from the natural objects.
The descriptions are in several parts of his work alphabeti-

114

BIOLOGY AND ITS MAKERS

cally arranged, for convenience of reference, and thus ani-
mals that were closely related are often widely separated.

Gesner (Fig. 32) sacrificed his life to professional zeal
during the prevalence of the plague in Zurich in 1 564. Hav-
ing greatly overworked in the care of the sick, he was seized
with the disease, and died at the age of forty-nine.

Considered from the standpoint of descriptions and illus-
trations, Gesner's Historia Animalium remained for a long

Fig. 32. — Gesner 1516-1565.

time the best work in zoology. He was the best zoologist
between Aristotle and John Ray, the immediate predecessor
of Linnaeus.

Jonston and Aldrovandi. — At about the same period as
Gesner's work there appeared two other voluminous publica-
tions, which are well known — those of Jonston, the Scot

LINNvEUS AND NATURAL HISTORY "5

{Historia Animalium, 1 549-1 553), and Aldrovandi, the
Italian {Opera, 1599-1606). The former consisted of four
foh'o volumes, and the latter of thirteen, of ponderous size,
to which was added a fourteenth on plants. Jonston's works
were translated, and were better known in England than those
of Gesner and Aldrovandi. The wood -engravings in Aldro-
vandi's volume are coarser than those of Gesner, and are by
no means so lifelike. In the Institute at Bologna are pre-
served twenty volumes of figures of animals in color, which
were the originals from which the engravings were made.
These are said to be much superior to the reproductions.
The encyclopaedic nature of the writings of Gesner, Aldro-
vandi, and Jonston has given rise to the convenient and
expressive title of the encyclopaedists.

Ray. — John Ray, the forerunner of Linnaeus, built upon
the foundations of Gesner and others, and raised the natural-
history edifice a tier higher. He greatly reduced the bulk
of publications on natural history, sifting from Gesner and
Aldrovandi their irrelevancies, and thereby giving a more
modern tone to scientific writings. He was the son of a
blacksmith, and was born in southern England in 1628.
The original form of the family name was Wray. He was
graduated at the University of Cambridge, and became a
fellow of Trinity College. Here he formed a friendship with
Francis Willughby, a young man of wealth whose tastes for
natural history were like his own. This association proved
a happy one for both parties. Ray had taken orders in the
Church of England, and held his university position as a
cleric; but, from conscientious scruples, he resigned his
fellowship in 1662. Thereafter he received financial assist-
ance from Willughby, and the two men traveled extensively
in Great Britain and on the Continent, with the view of inves-
tigating the natural history of the places that they visited.
On these excursions Willughby gave particular attention to

Ii6

BIOLOGY AND ITS MAKERS

animals and Ray to plants. Of Ray's several publications
in botany, his Historia Plantarum in three volumes (1686-
1704) is the most extensive. In another work, as early as
1682, he had proposed a new classification of plants, which

Fig. 33. — John Ray, 1628-1705.

in the next century was adopted by Jussieu, and which gives
Ray a place in the history of botany.

Willughby died in 1662, at the age of thirty-eight, leaving
an annuity to Ray, and charging him with the education of

LINN^US AND NATURAL HISTORY H?

his two sons, and the editing of his manuscripts. Ray per-
formed these duties as a faithful friend and in a generous
spirit. He edited and puWished Willughby's book on birds
(1678) and fishes (1686) with important additions of his ow^n,
for which he sought no credit.

After completing his tasks as the literary executor of Wil-
lughby, he returned in 1678 to his birthplace and continued
his studies in natural history. In 1691 he published "The
Wisdom of God manifested in the Works of the Creation,"
which was often reprinted, and became the forerunner of the
works on natural theology like Paley's, etc. This was an
amplification of ideas he had embodied in a sermon thirty-
one years earlier, and which at that time attracted much
notice. He now devoted himself Largely to the study of ani-
mals, and in 1693 published a w^ork on the quadrupeds and
serpents, a work which gave him high rank in the history of
the classification of animals. He died in 1705, but he had
accomplished much good work, and was not forgotten. In
1844 there was founded, in London, in his memory, the Ray
Society for the publication of rare books on botany and
zoology.

Ray's Idea of Species. — One of the features of Ray's
work, in the light of subsequent development, is of special
interest, and that is his limiting of species. He was the first
to introduce into natural history an exact conception of
species. Before his time the word had been used in an
indefinite sense to embrace groups of greater or less extent,
but Ray applied it to individuals derived from similar par-
ents, thus making the term species stand for a particular kind
of animal or plant. He noted some variations among species,
and did not assign to them that unvarying and constant char-
acter ascribed to them by Linnaeus and his followers. Ray
also made use of anatomy as the foundation for zoological
classification, and introduced great precision and clearness

Il8 BIOLOGY AND ITS MAKERS

into his definitions of groups of animals and plants. In the
particulars indicated above he represents a great advance
beyond any of his precursors, and marks the parting of the
ways between mediaeval and modem natural history.

In Germany Klein (1685-1759) elaborated a system of
classification embracing the entire animal kingdom. His
studies were numerous, and his system would have been of
much wider influence in molding natural history had it not
been overshadowed by that of I^innaeus.

Linnaeus or Linne. — The service of Linnaeus to natural
history was unique. The large number of specimens of
animals and plants, ever increasing through the collections
of travelers and naturalists, were in a confused state, and
there was great ambiguity arising from the lack of a method-
ical way of arranging and naming them. They were known
by verbose descriptions and local names. No scheme had
as yet been devised for securing uniformity in applying names
to them. The same animal and plant had different names
in the different sections of a country, and often different
plants and animals had the same name. In different coun-
tries, also, their names were greatly diversified. What was
especially needed was some great organizing mind to cata-
logue the animals and plants in a systematic way, and to give
to natural science a common language. Linnaeus possessed
this methodizing mind and supplied the need. While he did
little to deepen the knowledge of the organization of animal
and plant life, he did much to extend the number of known
forms; he simplified the problem of cataloguing them, and he
invented a simple method of naming them which was adopted
throughout the world. By a happy stroke he gave to biology
a new language that remains in use to-day. The tremendous
influence of this may be realized when we rem^ember that
naturalists everyv/here use identical names for the same
animals and plants. The residents of Japan, of Italy, of

LINN^US AND NATURAL HISTORY II9

Spain, of all the world, in fact, as was just said, employ the
same Latin names in classifying organic forms.

He also inspired many students with a love for natural
history and gave an impulse to the advance of that science
w^iich was long felt. We can not gainsay that a higher class
of service has been rendered by those of philosophic mind
devoted to the pursuit of comparative anatomy, but the step
of Linnaeus was a necessary one, and aided greatly in the
progress of natural history. Without this step the discoveries
and observations of others would not have been so readily
understood, and had it not been for his organizing force all
natural science would have been held back for want of a
common language. A close scrutiny of the practice among
naturalists in the time of Linnaeus shows that he did not
actually invent the binomial nomenclature, but by adopting
the suggestions of others he elaborated the system of classifi-
cation and brought the new language into common use.

Personal History. — Leaving for the present the system of
Linnaeus, we shall give attention to the personal history of
the man. The great Swedish naturalist was born in Rashult
in 1 707. His father was the pastor of the village, and intended
his eldest son, Carl, for the same high calling. The original
family name was Ignomarsen, but it had been changed to Lin-
delius, from a tall linden-tree growing in that part of the coun-
try. In 1761 a patent of nobility was granted by the crown
to Linnaeus, and thereafter he was styled Carl von Linne.

His father's resources were very limited, but he man-
aged to send his son to school, though it must be confessed
that young Linnaeus showed little liking for the ordinary
branches of instruction. His time was spent in collecting
natural-history specimens, and his mind was engaged in
thinking about them. The reports of his low scholarship
and the statement of one of his teachers that he showed no
aptitude for learning were so disappointing to his father that,

I20 BIOLOGY AND ITS MAKERS

in 1726, he prepared to apprentice Carl to a shoemaker, but
was prevented from doing so through the encouragement
of a doctor who, being able to appreciate the quality of mind
possessed by the young Linnaeus, advised allowing him to
study medicine instead of preparing for theology.

Accordingly, with a sum amounting to about $40, all his
father could spare, he set off for the University of Lund, to
pursue the study of medicine. He soon transferred to the
University of Upsala, where the advantages were greater. His
poverty placed himunder thegreatest straits for the necessities
of life, and he enjoyed no luxuries. While in the university
he mended his shoes, and the shoes which were given to him
by some of his companions, with paper and birch-bark, to
keep his feet from the damp earth. But his means did not
permit of his taking his degree at Upsala, and it was not until
eight years later, in 1735, that he received his degree in Holland.

At Upsala he was relieved from his extreme poverty by
obtaining an assistant's position, and so great was his knowl-
edge of plants that he was delegated to read the lectures of
the aged professor of botany, Rudbeck.

In 1732 he was chosen by the Royal Society of Upsala to
visit Lapland as a collector and observer, and left the univer-
sity without his degree. On returning to Upsala, his lack
of funds made itself again painfully felt, and he undertook
to support himself by giving public lectures on botany, chem-
istry, and mineralogy. He secured hearers, but the con-
tinuance of his lectures was prevented by one of his rivals on
the ground that Linnaeus had no degree, and was therefore
legally disqualified from taking pay for instruction. Pres-
ently he became tutor and traveling companion of a wealthy
baron, the governor of the province of Dalecarlia, but this
employment was temporary.

Helped by His Fiancee. — His friends advised him to
secure his medical degree and settle as a practitioner. Al-

LINN^US AND NATURAL HISTORY 121

though he lacked the necessarv funds, one circumstance con-
tributed to bring about this end: he had formed an attach-
ment for the daughter of a weahhy physician, named More
or Moraeus, and on applying for her hand in marriage, her
father made it a condition of his consent that Linnaeus should
take his medical degree and establish himself in the practice
of medicine. The young lady, who was thrifty as well as
handsome, offered her savings, amounting to one hundred
dollars (Swedish), to her lover. He succeeded in adding to
this sum by his own exertions, and with thirty-six Swedish
ducats set off for Holland to qualify for his degree. He had
practically met the requirements for the medical degree by
his previous studies, and after a month's residence at the
University of Hardewyk, his thesis was accepted and he was
granted the degree in June, 1735, in the twenty-eighth year
of his age.

Instead of returning at once to Sweden, he went to
Leyden, and made the acquaintance of several well-known
scientific men. He continued his botanical studies with great
energy, and now began to reap the benefits of his earlier
devotion to natural history. His heart-breaking and harass-
ing struggles were now over.

The Systema Naturae. — He had in his possession the
manuscript of his Systema NaturcF, and with the encourage-
ment of his new friends it was published in the same year.
The first edition (1735) of that notable work, which was
afterward to bring him so much fame, consisted of twelve
printed folio pages. It was merely an outline of the arrange-
ments of plants, animals, and minerals in a methodical cat-
alogue. This work passed through twelve editions during
his lifetime, the last one appearing in 1768. After the first
edition, the books were printed in octavo form, and in the
later editions were greatly enlarged. A copy of the first
edition was sent to Boerhaave, the most distinguished pro-

122 BIOLOGY AND ITS MAKERS

fessor in the University of Leyden, and secured for Linnaeus
an interview with that distinguished physician, who treated
him with consideration and encouraged him in his work.
Boerhaave was already old, and had not long to live; and
when Linnaeus was about to leave Holland in 1738, he ad-
mitted him to his sick-chamber and bade him a most affec-
tionate adieu, and encouraged him to further work by most
kindly and appreciative expressions.

Through the influence of Boerhaave, Linnaeus became the
medical attendant of Cliffort, the burgomaster at Amsterdam,
who had a large botanic garden. Cliffort, being desirous of
extending his collections, sent Linnaeus to England, where
he met Sir Hans Sloane and other eminent scientific men of
Great Britain. After a short period he returned to Holland,
and in 1 737 brought out the Genera Plantarum, a very original
work, containing an analysis of all the genera of plants. He
had previously published, besides the Sy sterna Naturce, his
Fundamenta Botanica, 1735, and Bibliotheca Boianica, 1736,
and these works served to spread his fame as a botanist
throughout Europe.

His Wide Recognition. — ^An illustration of his wide rec-
ognition is afforded by an anecdote of his first visit to Paris
in 1738. "On his arrival he went first to the Garden of
Plants, where Bernard de Jussieu was describing some
exotics in Latin. He entered w^ithout opportunity to intro-
duce himself. There was one plant which the demonstrator
had not yet determined, and which seemed to puzzle him.
The Swede looked on in silence, but observing the hesitation
of the learned professor, cried out 'Hcec planta jaciem Ame-
ricanam habet.^ ' It has the appearance of an American plant.'
Jussieu, surprised, turned about quickly and exclaimed 'You
are Linnaeus.' 'I am, sir,' was the reply. The lecture was
stopped, and Bernard gave the learned stranger an affec-
tionate welcome."

LINN^US AND NATURAL HISTORY I23

Return to Sweden. — After an absence of three and one-
half years, Linnaeus returned to his native country in 1 738, and
soon after was married to the young woman who had assisted
him and had waited for him so loyally. He settled in Stock-
holm and began the practice of medicine. In the period of
his absence he had accomplished much : visited Holland,
England, and France, formed the acquaintance of many
eminent naturalists, obtained his medical degree, published
numerous w^orks on botany, and extended his fame over all
Europe. In Stockholm, however, he w^as for a time neglected,
and he would have left his native country in disgust had it
not been for the dissuasion of his wife.

Professor in Upsala. — In i 741 he was elected professor
of anatomy in the University of Upsala, but by a happy stroke
was able to exchange that position for the professorship of
botany, materia medica, and natural history that had fallen
to his former rival, Rosen. Linnaeus was now in his proper
element; he had opportunity to lecture on those subjects to
which he had been devotedly attached all his life, and he
entered upon the work with enthusiasm.

He attracted numerous students by the power of his per-
sonal qualities and the excellence of his lectures. He became
the most popular professor in the University of Upsala, and,
owing to his drawing power, the attendance at the university
was greatly increased. In 1749 he had 140 students devoted
to studies in natural histor)\ The number of students at
the university had been about 500; " whilst he occupied the
chair of botany there it rose to 1,500." A part of this in-
crease w^as due to other causes, but Linnaeus was the greatest
single drawing force in the university. He was an eloquent
as well as an enthusiastic lecturer, and he aroused great in-
terest among his students, and he gave an astonishing impulse
to the study of natural history in general, and to botany in par-
ticular. Thus Linnaeus, after having passed through great

124 BIOLOGY AND ITS MAKERS

privations in his earlier years, found himself, at the age of
thirty-four, established in a position which brought him rec-
ognition, honor, and large emolument.

In May, 1907, the University of Upsala celebrated the
two hundredth anniversary of his birth with appropriate cer-

FiG. 34. — LiNN^us AT Sixty, 1707-1778.

emonies. Delegations of scientific men from all over the
world were in attendance to do honor to the memory of the
great founder of biological nomenclature.

LINN^US AND NATURAL HISTORY 12$

Personal Appearance. — The portrait of liinnaeus at the
age of sixty is shown in Fig. 34. He was described as of
" medium height, with large limbs, brown, piercing eyes, and
acute vision." His hair in early youth was nearly white, and
changed in his manhood to brown, and became gray with
the advance of age. Although quick-tempered, he was natu-
rally of a kindly disposition, and secured the affection of his
students, with whom he associated and Vv^orked in the most
informal way. His love of approbation was very marked,
and he was so much praised that his desire for fame became
his dominant passion. The criticism to which his work was
subjected from, time to time accordingly threw him into
fits of despondency and rage.

His Influence upon Natural History. — However much we
miay admire the industry and force of Linnxus, we must
admit that he gave to natural history a one-sided develop-
ment, in which the more essential parts of the science received
scant recognition. His students, like their master, w^ere
mainly collectors and classifiers. "In their zeal for naming
and classifying, the higher goal of investigation, knowl-
edge of the nature of animals and plants, was lost sight of
and the interest in anatomy, physiology, and embryolog}^
lagged."

R. Hertwig says of him: "For while he in his Sy sterna
Naturce treated of an extraordinarily larger number of ani-
mals than any earlier naturalist, he brought about no deep-
ening of our knowledge. The manner in which he divided
the animal kingdom, in comparison with the Aristotelian
system, is to be called rather a retrogression than an advance.
Tinnaeus divided the animal kingdom into six classes — Mam-
malia, Aves, Amphibia, Pisces, Insecta, Vermes. The first
four classes correspond to Aristotle's four groups of animals
with blood. In the division of the invertebrated animals into
Insecta and Vermes Linnaeus stands undoubtedly behind

126 BIOLOGY AND ITS MAKERS

Aristotle, who attempted, and in part indeed successfully, to
set up a larger number of groups.

"But in his successors even more than in Linnaeus himself
we see the damage wrought by the purely systematic method
of consideration. The diagnoses of Linnaeus were for the
most part models, which, mutatis ynutandis, cowliXh^ employed
for new species with little trouble. There was needed only
some exchanging of adjectives to express the differences.
With the hundreds of thousands of different species of
anim.als, there was no lack of material, and so the arena was
opened for that spiritless zoology of species-making, which
in the first half of the nineteenth century brought zoology
into such discredit. Zoology would have been in danger of
growing into a Tower of Babel of species-description if a
counterpoise had not been created in the strengthening of the
physiologico-anatomical method of consideration."

His Especial Service. —Nevertheless, the vrork of Lin-
naeus made a lasting impression upon natural history, and we
shall do well to get clearly in mind the nature of his particular
service. In the first place, he brought into use the method
of naming animals and plants which is employed to-day. Li
his Sysiema NaturcB and in other publications he employed
a means of naming every natural production in two words^
and it is therefore called the binomial nomenclature. An
illustration will make this clearer. Those animals which had
close resemblance, like the lion, tiger, leopard, the lynx, and
the cat, he united under the common generic name of Felis^
and gave to each a particular trivial name, or specific nam.e.
Thus the name of the lion became Felis leo, of the tiger Felis
tigris, of the leopard Felis pardus, of the cat Felis calus ; and
to these the modern zoologists have added, making the
Canada lynx Felis Canadensis^ the domestic cat Fells domes-
iicata, etc. In a similar way, the dog-like animals were
united into a genus designated Canis, and the particular

LINN^US AND NATURAL HISTORY 127

kinds or species became Canis lupus, the wolf, Canis vulpes^
the fox, Canis jamiliaris, the common dog. This simple
method took the place of the var}dng names applied to the
same animal in different countries and local names in the
same country. It recognized at once their generic likeness
and their specific individuality.

All animals, plants, and minerals were named according
to this method. Thus there were introduced into nomencla-
ture two groups, the genus and the species. The name of
the genus was a noun, and that of the species an adjective
agreeing with it. In the choice of these names Linnaeus.-
sought to express some distinguishing feature that would be
suggestive of the particular animal, plant, or mineral. The
trivial, or specific, names were first employed by Linnaeus in
1749, and were introduced into his Species Plantarum in
1753, and into the tenth edition of his Systema Naturce in

1758.

We recognize Tinna^us as the founder of nomenclature in
natural history, and by the common consent of naturalists,
the date 1758 has come to be accepted as the starting-point
for determining the generic and specific names of animals..
The much vexed question of priority of names for animals is-
settled by going back to the tenth edition of his Systema Na-
/«r^,v/hile the botanists have adopted his Species Plantarum,.
1753, as their base-line for names. As to his larger divisions,
of animals and plants, he recognized classes and orders. Then
came genera and species. Linnaeus did not use the term
family in his formulae; this convenient designation was lirst
used and introduced in 1780 by Batch.

The Systema Naturce is not a treatise on the organization
of animals and plants ; it is rather a catalogue of the produc-
tions of nature methodically arranged. His aim in fact was.
not to give full descriptions, but to make a methodical,
arrangement.

128 BIOLOGY AND ITS MAKERS

To do justice, however, to the discernment of Linnaeus, it
should be added that he was fully aware of the artificial
nature of his classification. As Kerner has said: ''It is not
the fault of this accomplished and renowned naturalist if a
greater importance were attached to his system than he him-
self ever intended. Linnaeus never regarded his twenty-four
classes as real and natural divisions of the vegetable kingdom,
and specifically says so ; it was constructed for convenience of
reference and identification of species. A real natural system,
founded on the true affinities of plants as indicated by the
structural characters, he regarded as the highest aim of botan-
ical endeavor. He never completed a natural system, leaving
only a fragment (published in 1738)."

Terseness of Descriptions. — His descriptions were marked
by extreme brevity, but by great clearness. This is a second
feature of his work. In giving the diagnosis of a form he
was very terse. He did not employ fully formed sentences
containing a verb, but words concisely put together so as to
bring out the chief things he wished to emphasize. As an
illustration of this, we may take his characterization of the
forest rose, ^^ Rosa sylvestris vulgaris, jlore odorata incarnato.''^
The common rose of the forest with a flesh-colored, sweet-
smelling flower. In thus fixing the attention upon essential
points he got rid of verbiage, a step that was of very great
importance.

His Idea of Species. — A third feature of his work was
that of emphasizing the idea of species. In this he built
upon the work of Ray. We have already seen that Ray
was the first to define species and to bring the conception
into natural history. Ray had spoken of the variability of
species, but Linnaeus, in his earUer publications, declared
that they were constant and invariable. His conception of a
species was that of individuals born from similar parents.
It was assumed that at the original stocking of the earth, one

LINN^US AND NATURAL HISTORY 129

pair of each kind of animals was created, and that existing
species were the direct descendants without change of form
or habit from the original pair. As to their number, he said :
^^ Species tot sunt, quot jormce ah initio created sunt^^ — there
are just so many species as there were forms created in the
beginning; and his oft-quoted remark, "iVw//a species nova,^^
indicates in terse language his position as to the formation of
new species. Linnaeus took up this idea as expressing the cur-
rent thought, without analysis of what was involved in it. He
readily might have seen that if there were but a single pair
of each kind, some of them must have been sacrificed to
tlie hunger of the carnivorous kinds ; but, better than making
any theories, he might have looked for evidence in nature as
to the fixity of species.

While Linnaeus first pronounced upon the fixity of species,
it is interesting to note that his extended observations upon
nature led him to see that variation among animals and plants
is common and extensive, and accordingly in the later editions
of his Systema Nattirce we find him receding from the position
that species are fixed and constant. Nevertheless, it was
owing to his influence, more than to that of any other writer
of the period, that the dogma of fixity of species was estab-
lished. His great contemporary Buffon looked upon species
as not having a fixed reality in nature, but as being fig-
ments of the imagination ; and we shall see in a later section
of this book how the idea of Linnaeus in reference to the
fixity of species gave way to accumulating evidence on the
matter.

Summary. — The chief services of Linnaeus to natural
science consisted of these three things : bringing into current
use the binomial nomenclature, the introduction of terse
formulae for description, and fixing attention upon species.
The first two were necessary steps ; they introduced clearness
and order into the management of the immense number of

130 BIOLOGY AND ITS MAKERS

details, and they made it possible for the observations and
discoveries of others to be understood and to take their place
in the great system of which he was the originator. The
effect of the last step was to direct the attention of naturalists
to species, and thereby to pave the way for the coming con-
sideration of their origin, a consideration which became such
a burning Ci[uestion in the last half of the nineteenth century.

Reform of the Linn^an System

Necessity of Reform. — ^As indicated above, the classifica-
tion established by Linnaeus had grave defects; it was not
founded on a knowledge of the comparative structure of
animals and plants, but in many instances upon superficial
features that were not distinctive in determining their position
and relationships. His system was essentially an artificial
one, a convenient key for finding the names of animals and
plants, but doing violence to the natural arrangement of those
organisms. An illustration of this is seen in his classification
of plants into classes, mainly on the basis of the number of
stamens in the flower, and into orders according to the number
of pistils. Moreover, the true object of investigation was
obscured by the Linnaean system. The chief aim of bio-
logical study being to extend our knowledge of the structure,
development, and physiology of animals and plants as a
means of understanding more about their life, the arrange-
ment of animals and plants into groups should be the out-
come of such studies rather than an end in itself.

It was necessary to follow different methods to bring
natural histor}^ back into the line of true progress. The first
modification of importance to the Linnaean system was that
of Cuvier, who proposed a grouping of animals based upon
a knowledge of their comparative anatomy. He declared

LINN^US AND NATURAL HISTORY 131

that animals exhibit four types of organization, and his types
were substituted for the primary groups of Linnaeus.

The Scale of Being. — In order to understand the bearing
of Cuvier's conclusions we must take note of certain views
regarding the animal kingdom that were generally accepted
at the time of his w-riting. Between Linnceus and Cuvier
there had emerged the idea that all animals, from the lowest
to the highest, form a graduated series. This grouping of
animals into a linear arrangement was called exposing the
Scale of Being, or the Scale of Nature (Scala Naturce).
Buffon, Lamarck, and Bonnet were among the chief ex-
ponents of this idea.

That Lamarck's connection with it was temporary has
been generally overlooked. It is the usual statement in the
histories of natural science, as in the Encyclopcedia Britannica,
in the History of Carus, and in Thomson's Science oj Lije,
that the idea of the scale of nature found its fullest expression
in Lamarck. Thomson says : " His classification (1801-1812)
represents the climax of the attempt to arrange the groups
of animals in linear order from lower to higher, in what was
called a scala naturce^^ (p. 14). Even so careful a writer as
Richard Hertwig has expressed the matter in a similar form.
Now, while Lamarck at first adopted a linear classification,
it is only a partial reading of his works that will support the
conclusion that he held to it. In his Systeme des Animaux
sans Vertebres, published in 1801, he arranged animals in
this way; but to do credit to his discernment, it should be
observed that he was the first to employ a genealogical tree
and to break up the serial arrangement of animal forms. In
1809, in the second volume of his Philosophie Zoologique,
as Packard has pointed out, he arranged animals according
to their relationships, in the form of a trunk with divergent
branches. This was no vague suggestion on his part, but
an actual pictorial representation of the relationship between

132 BIOLOGY AND ITS MAKERS

different groups of animals, as conceived by him. Although
a crude attempt, it is interesting as being the first of its kind.
This is so directly opposed to the idea of scale of being that
we make note of the fact that Lamarck forsook that view at
least twenty years before the close of his life and substituted
for it that of the genealogical tree.

Lamarck's Position in Science. — Lamarck is coming into
full recognition for his part in founding the evolution theor}',
but he is not generally, as yet, given due credit for his work
in zoology. He was the most philosophical thinker engaged
with zoology at the close of the eighteenth and the beginning
of the nineteenth century. He was greater than Cuvier in
his reach of intellect and in his discernment of the true
relationships among living organisms. We are to recollect
that he forsook the dogma of fixity of species, to which Cuvier
held, and founded the first comprehensive theory of organic
evolution. To-day we can recognize the superiority of his
mental grasp over that of Cuvier, but, owing to the personal
magnetism of the latter and to his position, the ideas of
Lamarck, which Cuvier com.bated, received but little atten-
tion when they were promulgated. We shall have occasion
in a later chapter to speak more fully of Lamxarck's contribu-
tion to the progress of biological thought.

Cuvier's Four Branches. — We now return to the type-
theory of Cuvier. By extended studies in comparative anat-
omy, he came to the conclusion that animals are constructed
upon four distinct plans or types: the vertebrate type; the
moUuscan type; the articulated type, embracing animals with
joints or segments; and the radiated type, the latter with a
radial arrangement of parts, like the starfish; etc. These
types are distinct, but their representatives, instead of forming
a linear series, overlap so that the lowest forms of one of the
higher groups are simpler in organization than the higher
forms of a lower group. This was very illuminating, and,

LINN^US AND NATURAL HISTORY 133

being founded upon an analysis of structure, was important.
It was directly at variance with the idea of scale of being, and
overthrew that doctrine.

Cuvier first expressed these views in a pamphlet ])ublished
in 1795, and later in a better-known paper read before the
French Academy in 181 2, but for the full development of
his type-theor}^ we look to his great volume on the animal
kingdom published in 1816. The central idea of his arrange-
ment is contained in the secondary title of his book, "The
Animal Kingdom Arranged According to its Organization '^
{Le Re gne Animal Distrihued'aprhs son Organisation, 1816).
The expression "arranged according to its organization"
embraces the feature in which this analysis of animals differs
from all previous attempts.

Correlation of Parts. — ^An important idea, first clearly
expressed by Cuvier, was that of correlation of parts. The
view that the different parts of an animal are so correlated
that a change in one, brought about through changes in use,
involves a change in another. For illustration, the cleft hoof
is always associated with certain forms of teeth and with the
stomach of a ruminant. The sharp claws of flesh-eating
animals are associated with sharp, cutting teeth for tearing
the flesh of the victims, and with an alimentary tube adapted
to the digestion of -a fleshy diet. Further account of Cuvier
is reserved for the chapter on the Rise of Comparative Anat-
omy, of which he was the founder.

Von Baer. — The next notable advance affecting natural
history came through the work of Von Baer, who, in 1828,
founded the science of development of animal forms. He
arrived at substantially the same conclusions as Cuvier.
Thus the system founded upon - comparative anatomy by
Cuvier came to have the support of Von Baer's studies in
embr}^ology.

The contributions of these men proved to be a turning-

134 BIOLOGY AND ITS MAKERS

point in natural history, and subsequent progress in system-
atic botany and zoology resulted from the application of the
methods of Cuvier and Von Baer, rather than from following
that of Linnaeus. His nomenclature remained a permanent
contribution of value, but the knowledge of the nature of
living forms has been advanced chiefly by studies in com-
parative anatomy and embryology, and, also, in the applica-
tion of experiments.

The most significant advances in reference to the class-
ification of animals was to come as a result of the accept-
ance of the doctrine of organic evolution, subsequent to
1859. Then the relationships between animals were made
to depend upon community of descent, and a distinction
was drawn between superficial or apparent relationships
and those deep-seated characteristics that depend upon close
genetic aihnities.

Alterations by Von Siebold and Leuckart. — But, in the
mean time, naturalists were not long in discovering that the
primary divisions established by Cuvier were not well bal-
anced, and, indeed, that they were not natural divisions of
the animal kingdom. The group Radiata was the least
sharply defined, since Cuvier had included in it not only those
animals which exhibit a radial arrangement of parts, but also
unicellular organisms that were asymmetrical, and some of
the worms that showed bilateral symmetry. Accordingly,
Karl Th. von Siebold, in 1845, separated these animals and
redistributed them. For the simplest unicellular animals he
adopted the name Protozoa, which they still retain, and the
truly radiated forms, as starfish, sea-urchins, hydroid polyps,
coral animals, etc., were united in the group Zoophyta. Von
Siebold also changed Cuvier's branch, Articulata, separating
those forms as Crustacea, insects, spiders, and myriopods,
which have jointed appendages, into a natural group called
Arthropoda, and uniting the segmented worms with those

LINN^US AND NATURAL HISTORY

135

worms that Cuvier has included in the radiate group, into
another branch called Vermes. This separation of the four
original branches of Cuvier was a movement in the right
direction, and v/as destined to be carried still farther.

Fig. 35. — Karl Th. von Siebold, 1804-1885.

Von Siebold (Fig. 35) was an important man in the
progress of zoology, especially in reference to the comparative
anatomy of the invertebrates.

Leuckart (Fig. 36), whose fame as a lecturer and teacher

136

BIOLOGY AND ITS MAKERS

attracted many young men to the University of Leipsic, is
another conspicuous personality in zoological progress.

This distinguished zoologist, following the lead of Von
Siebold, made further modifications. He split Von Siebold's
group of Zoophytes into two distinct kinds of radiated animals:

Fig. 36. — Rudolph Leuckart, 1823-1898.

the star-fishes, sea-urchins, sea-cucumbers, etc., Imving a
spiny skin, he designated Echinoderma; the jelly-fishes,,
polyps, coral animals, etc., not possessing a true body cavity ^
were also united into a natural group, for v/hich he proposed
the name Coelenterata.

From all these changes there resulted the seven primary

LINN^US AND NATURAL HISTORY 137

divisions— branches, subkingdoms, or phyla — ^v^^hich, with
small modifications, are still in use. These are Protozoa,
Coelenterata, Echinoderma, Vermes, Arthropoda, Mollusca,
Vertebrata. These seven phyla are not entirely satisfactory,
and there is being carried on a redistribution of forms, as in
the case of the brachiopods, the sponges, the tunicates, etc.
While all this makes toward progress, the changes are of
more narrow compass than those alterations due to Von
Siebold and Leuckart.

Summary. — In reviewing the rise of scientific natural
history, we observe a steady development from the time of
the Physiologus, first through a return to Aristotle, and
through gradual additions to his observations, notably by
Gesner, and then the striking improvements due to Ray and
Linnaeus. We may speak of the latter two as the founders
of systematic botany and zoology. But the system left by
Linnaeus was artificial, and the greatest obvious need was to
convert it into a natural system founded upon a knowledge
of the structure and the development of living organisms.
This was begun by Cuvier and Von Baer, and was continued
especially by Von Siebold and Leuckart. To this has been
added the study of habits, breeding, and adaptations of or-
ganisms, a study which has given to natural history much
greater importance than if it stood merely for the systematic
classification of animals and plants.

Tabular View of Classifications. — ^A table showing the
primar}^ groups of Linnaeus, Cuvier, Von Siebold, and
Leuckart will be helpful in picturing to the mind the modifi-
cations made in the classification of animals. Such a table
is given on the following page.

L. Agassiz, in his famous essay on Classification, reviews
in the most scholarly way the various systems of classifica-
tion. One peculiar feature of Agassiz's philosophy was his
adherence to the dogma of the fixity of species. The same

133

BIOLOGY AND ITS MAKERS

year that his essay referred to was published (1859) appeared
Darwin's Origin of Species. Agassiz, however, was never
able to accept the idea of the transformations of species.

Linnaeus

Cuvier

Von Siebold

Leuckart

Mammalia

Vertebrata

Vertebrata

Vertebrata

Aves

(Embracing five
classes: Mam-

(Embracing five
classes.)

(Five classes.)

Amphibia

malia, Aves, Rep-
tilia, Batrachia,

Pisces

Pisces.)

Insecta

MoUusca

Mollusca

Mollusca

(Including Crusta-
cea, etc.)

Articulata

( Arthropoda
( Vermes

Arthropoda

Vermes

(Including Mol-
lusca and all
lower forms.)

Radiata

r Zoophyta

( Protozoa

Vermes
\ Echinoderma
} Coelenterata

Protozoa

Steps in Biological Progress from Linn^us to Darwin

The period from Linnaeus to Darwin is one full of im-
portant advances for biology in general. We have considered
in this chapter only those features that related to changes in
the system of classification, but in the mean time the morpho-
logical and the physiological sides of biology were being ad-
vanced not only by an accumulation of facts, but by their
better analysis. It is an interesting fact that, although during
this period the details of the subject were greatly multiplied,
progress was relatively straightforward and by a series of
steps that can be clearly indicated.

It will be of advantage before the subject is taken up in
its parts to give a brief forecast in which the steps of prog-
ress can be represented in outline without the confusion
arising from the consideration of details. Geddes, in 1898,
pointed out the steps in progress, and the account that follows
is based upon his lucid analysis.

LINN^US AND NATURAL HISTORY 139

The Organism. — In the time of Linnaeus the attention of
naturalists was mainly given to the organism as a whole.
Plants and animals were considered from the standpoint of
the organism — the external features w^ere largely dealt with,
the habitat, the color, and the general appearance — features
which characterize the organism as a whole. Linnaeus and
Jussieu represent this phase of the work, and Buffon the
higher type of it. Modern studies in this line are like addi-
tion to the Systema Naturce.

Organs. — The first distinct advance came in investigating
animals and plants according to their structure. Instead
of the complete organism, the organs of which it is composed
became the chief subject of analysis. The organism was
dissected, the organs were examined broadly, and those of
one kind of animal and plant compared with another. This
kind of comparative study centered in Cuvier, w^ho, in the
early part of the nineteenth century, founded the science of
comparative anatomy of animals, and in Hofmeister, who
examined the structure of plants on a basis of broad com-
parison.

Tissues. — Bichat, the famous contemporary of Cuvier,
essayed a deeper level of analysis in directing attention to the
tissues that are combined to make up the organs. He dis-
tinguished tw^enty-one kinds of tissues by combinations of
which the organs are comxposed. This step laid the founda-
tion for the science of histology, or minute anatomy. Bichat
called it general anatomy {Anatomie Generate, 1801).

Cells. — Before long it was shown that tissues are not the
real units of structure, but that they are composed of micro-
scopic elements called cells. This level of analysis was not
reached until magnifying-lenses wxre greatly improved —
it was a product of a closer scrutiny of nature with improved
instruments. The foundation of the work, especially for
plants, had been laid by Leeuwenhoek, Malpighi, and Grew^

I40 BIOLOGY AND ITS MAKERS

But when the broad generah'zation, that all the tissues of
animals and plants are composed of cells, was given to the
world by Schleiden and Schwann, in 1838-39, the entire or-
ganization of living forms took on a new aspect. This was
progress in understanding the morphology of animals and
plants.

Protoplasm. — With improved microscopes and attention
directed to cells, it was not long before the discovery was
made that the cells as units of structure contain protoplasm.
That this substance is similar in plants and animals and is
the seat of all vital activity was determined chiefly by the
researches of Max Schultze, published in 1861. Thus step
by step, from 1758, the date of the tenth edition of the
System a Natures, to 1861, there was a progress on the mor-
phological side, passing from the organism as a whole to
organs, to tissues, to cells, and finally to protoplasm, the study
of which in all its phases is the chief pursuit of biologists.

The physiological side had a parallel development. In
the period of Linnaeus, the physiology of the organism was
investigated by Haller and his school; following him the
physiology of organs and tissues was advanced by J. Miiller,
Bichat, and others. Later, Virchow investigated the physiol-
ogy of cells, and Claude Bernard the chemical activities of
protoplasm.

This set forth in outline will be amplified in the follow-
ing chapters.

CHAPTER VII

CUVIER AND THE RISE OF COMPARATIVE
ANATOMY

After observers like Linnaeus and his followers had at-
tained a knowledge of the externals, it was natural that men
should turn their attention to the organization or internal
structure of living beings, and when the latter kind of inves-
tigation became broadly comparative, it blossomed into com-
parative anatomy. The materials out of which the science
of comparative anatomy was constructed had been long
accumulating before the advent of Cuvier, but the mass of
details had not been organized into a compact science.

As indicated in previous chapters, there had been an in-
creasing number of studies upon the structure of organisms,
both plant and animal, and there had resulted some note-
worthy monographs. All this work, however, was mainly
descriptive, and not comparative. Now and then, the com-
paring tendency had been shown in isolated writings such as
those of Harvey, Malpighi, and others. As early as 1555,
Belon had compared the skeleton of the bird with that of the
human body "in the same posture and as nearly as possible
bone for bone " ; but this was merely a faint foreshadowing
of what was to be done later in comparing the systems of the
more important organs.

We must keep in mind that the study of anatomy em-
braces not merely the bony framework of animals, but also
the muscles, the nervous system, the sense organs, and all the
other structures of both animals and plants. In the rise of

141

142

BIOLOGY AND ITS MAKERS

comparative anatomy there gradually emerged naturalists
who compared the structure of the higher animals with that
of the simpler ones. These comparisons brought out so
many resemblances and so many remarkable facts that anat-

FiG. 37. — Severinus, 1580-1656.

omy, which seems at first a dry subject, became endued with
great interest.

Severinus. — The first book expressly devoted to compara-
tive anatomy was that of Severinus (i 580-1656), designated

RISE OF COMPARATIVE ANATOMY 143

Zootomia DemocritcB. The title was derived from the Roman
naturalist Democritaeus, and the date of its publication, 1645,
places the treatise earlier than the works of Malpighi, Leeu-
wenhoek, and Swammerdam. The book is illustrated by
numerous coarse woodcuts, showing the internal organs of
fishes, birds, and some mammals. There are also a few-
illustrations of stages in the development of these animals.
The comparisons were superficial and incidental ; neverthe-
less, as the first attempt, after the revival of anatomy, to
make the subject comparative, it has some especial interest.
Severinus (Fig. 37) should be recognized as beginning the
line of comparative anatomists which led up to Cuvier.

Forerunners of Cuvier. — ^Anatomical studies began to
take on broad features with the work of Camper, John
Hunter, and Vicq d'Azyr. These three men paved the way
for Cuvier, but it must be said of the two former that their
comparisons were limited and unsystematic.

Camper, whose portrait is shown in Fig. 38, was born in
Leyden, in 1722. He was a versatile man, having a taste
for drawing, painting, and sculpture, as well as for scientific
studies. He received his scientific training under Boerhaavc
and other eminent men in Leyden, and became a professor
and, later, rector in the University of Groningen. Possessing
an ample fortune, and also having married a rich wife, he
was in position to foilov/ his ov/n tastes. He travelled exten-
sively and gathered a large collection of skeletons. He
showed considerable talent as an anatomist, and he made
several discoveries, which, however, he did not develop, but
left to others. Perhaps the possession of riches was one of
his limitations; at any rate, he lacked fixity of purpose.

Among his discoveries may be mentioned the semicircu-
lar canals in the ear of fishes, the fact that the bones of flying
birds are permeated by air, the determination of some fossil
bones, with the suggestion that they belonged to extinct forms.

144

BIOLOGY AND ITS MAKERS

The latter point is of interest, as antedating the conchisions
of Cuvier regarding the nature of fossil bones. Camper also
made observations upon the facial angle as an index of in-
telligence in the different races of mankind, and in lower

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if ■

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mki/snf

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Fig. 38. — Camper, i 722-1 789.

animals. He studied the anatomy of the elephant, the whale,
the orang, etc.

John Hunter (1728-1793), the gifted Scotchman whose
museum in London has been so justly celebrated, was a man
of extraordinary originality, who read few books but went
directly to nature for his facts ; and, although he made errors
from which he would have been saved by a wider acquaint-

RISE OF COMPARATIVE ANATOMY

145

ance with the writings of naturalists, his neglect of reading
left his mind unprejudiced by ihe views of others. He was
a wild, unruly spirit, who would not be forced into the con-
ventional mold as regards either education or manners.
His okicr brother, William, a man of more elegance and
refinement, who well understood the value of polish in refer-

FiG. 39. — John Hunter, i 728-1 793.

ence to worldly success, tried to improve John by arranging
for him to go to the University of Oxford, but John rebelled
and would not have the classical education of the university,
nor would he take on the refinements of taste and manner of
which his brother was a good example. *' Why," the doughty
John is reported to have said, " they wanted to make me study

146 BIOLOGY AND ITS MAKERS

Greek! They tried to make an old woman of me!" How-
ever much lack of appreciation this attitude indicated, it
shows also the Philistine independence of his spirit. This
independence of mind is one of his striking characteristics.

This is not the place to dwell upon tlie unfortunate con-
troversy that arose betv/een these two illustrious brothers
regarding scientific discoveries claimed by each. The posi-
tion of both is secure in the historical development of medicine
and surgery. Although the work of John Hunter Avas largely
medical and surgical, he also made extensive studies on the
comparative anatomy of animals, and has a place as one of
the most conspicuous predecessors of Cuvier. He was very
energetic both in making discoveries and in adding to his
great museum.

The original collections made by Hunter are still open to
inspection in the rooms of the Royal College of Surgeons,
London. It was his object to preserve specimens to illus-
trate the phenomena of life in all organisms, whether in
health or disease, and the extent of his museum may be
divined from the circumstance that he expended upon it
about three hundred and seventy-five thousand dollars. Al-
though he described and compared many types of animals,
it was as maich in bringing this collection together and leaving
it to posterity that he advanced comparative anatomy as in
what he wrote. After his death the House of Commons
purchased his museum for fifteen thousand pounds, and
placed it under the care of the corporation of Surgeons.
Hunter's portrait is shown in Fig. 39.

Vicq d'Azyr (P'ig. 40), more than any other man, holds
the chief rank as a comparative anatomist before the advent
of Cuvier into the same field. He was born in 1748, the son
of a physician, and went to Paris at the age of seventeen to
study medicine, remaining in the metropolis to the time of
his death in 1 794. He was celebrated as a physician, became

RISE OF COMPARATIVE ANATOMY 147

permanent secretary of the newly founded Academy of Med-
icine, consulting physician to the queen, and occupied other
positions of trust and responsibility. He married the niece
of Daubenton, and, largely through his influence, was ad-
vanced to social place and recognition. On the death of
Buffon, in 1788, he took the seat of that distinguished nat-
uralist as a member of the French Academ^y.

Fig. 40. — VicQ d'Azyr, i 748-1 794.

He made extensive studies upon the organization particu-
larly of birds and quadrupeds, making comparisons between
their structure, and bringing out new points that were supe-
rior to anything yet published. His comparisons of the limbs
of man and animals, showing a correspondence between the
flexor and extensor muscles of the legs and arms, were made
with great exactness, and they served to mark the beginning
of a new kind of precise comparison. These were not merely
fanciful comiparisons, but exact ones — part for part; and
his general considerations based upon these comparisons were
of a brilliant character.

148 BIOLOGY AND ITS MAKERS

As Huxley has said, ''he may be considered as the founder
of the modern science of anatomy." His work on the struc-
ture of the brain v/as the most exact which had appeared up
to that time, and in his studies on the brain he entered into
broad comparisons as he had done in the study of the other
parts of the animal organization.

He died at the age of forty-six, without being able to
complete a large work on human anatomy, illustrated with
colored figures. This work had been announced and en-
tered upon, but only that part relating to the brain had
appeared at the time of his death. Besides drawings of the
exterior of the brain, he made sections; but he was not able
to determine with any particular degree of accuracy the
course of fiber tracts in the brain. This was left for other
workers. He added many new facts to those of his pred-
ecessors, and by introducing exact comparisons in anatomy
he opened the field for Cuvier.

Cuvier. — When Cuvier, near the close of the eighteenth
century, committed himself definitely to the progress of
natural science, he found vast accumulations of separate
mionographs to build upon, but he undertook to dissect
representatives of all the groups of animals, and to found
his comparative anatomy on personal observations. The
work of Vicq d'Azyr marked the highest level of attain-
ment, and afforded a good model of what comparisons
should be; but Cuvier had even larger ideas in reference
to the scope of comparative anatomy than had his great
predecessor.

The particular feature of Cuvier's service was that in his
investigations he covered the whole field of animal organiza-
tion from the lowest to the highest, and uniting his results
with what had already been accomplished, he established
comparative anatomy on broad lines as an independent
branch of natural science. Almost at the outset he conceived

RISE OF COMPARATIVE ANATOMY 149

the idea of making a comprehensive study of the structure of
the animal kingdom. It was fortunate that he began his
investigations with thorough work upon the invertebrated
animals; for from this view-point there was gradually un-
folded to his great mind the plan of organization of the entire
series of animals. Not only is a knowledge of the structure
of the simplest animals an essential in understanding that of
the more modified ones, but the more delicate work required
in dissecting them gives invaluable training for anatomizing
those of more complex construction. The value attached to
this part of his training by Cuvier is illustrated by the advice
that he gave to a young medical student w^ho brought to his
attention a supposed discovery in anatomy. " Are you an
entomologist ? " inquired Cuvier. " No," said the young man.
"Then," replied Cuvier, ''go first and anatomize an insect,
and return to me; and if you still believe that your obser\^a-
tions are discoveries I will then believe you."

Birth and Early Education. — Cuvier was born in 1769,
at Montbeliard, a village at that tim^e belonging to Wurttem-
berg, but now a part of the French Jura. His father was a
retired militar}' officer of the Swiss army, and the family,
being Protestants, had moved to ^lontbeliard for freedom
from religious persecution. Cuvier was christened Leopold-
Christian-Frederic-Dagobert Cuvier, but early in youth took
the name of Georges at the wish of his mother, who had lost
an infant son by that name.

He gave an early promise of intellectual leadership, and
his mother, although not well educated, took the greatest
pains in seeing that he formed habits of industry and con-
tinuous work, hearing him recite his lessons in Latin and
other branches, although she did not possess a knovvledge of
Latin. He early showed a leaning toward natural history;
having access to the v/orks of Cesner and Buffon, he profited
by reading these two writers. So great was his interest that

150 BIOLOGY AND ITS MAKERS

he colored the plates in Buffon's Natural History from de-
scriptions in the text.

It was at first contemplated by his family that he should
prepare for theology, but failing, through the unfairness of
one of his teachers, to get an appointment to the theological
seminary, his education was continued in other directions.
He was befriended by the sister of the Duke of Wurttemberg,
who sent him as a pensioner to the famous Carolinian acad-
emy at Stuttgart. There he showed great application, and
with the wonderful memory with which he was endowed, he
took high rank as a student. Here he met Kielmeyer, a
young instructor only four years older than himself, who
shared his taste for natural history and, besides this, intro-
duced him to anatomy. In after-years Cuvier acknowledged
the assistance of Kielmeyer in determining his future work
and in teaching him to dissect.

Life at the Seashore. — In 1788 the resources of his
family, which had always been slender, became further re-
duced by the inability of the government to pay his father's
retiring stipend. As the way did not open for employ-
ment in other directions, young Cuvier took the post of in-
structor of the only son in the family of Count d'Hericy,
and went with the family to the sea-coast in Normandy,
near Caen. For six years (i 788-1 794) he lived in this noble
family, with much time at his disposal. For Cuvier this
period, from the age of nineteen to twenty-five, was one of
constant research and reflection.

While Paris was disrupted by the reign of terror, Cuvier,
who, although of French descent, regarded himself as a Ger-
man, was quietly carrying on his researches into the struQure
of the life at the seaside. These years of diligent study and
freedom from distractions fixed his destiny. Here at the
sea-coast, without the assistance of books and the stimulus
of intercourse with other naturalists, he was drawn directly

RISE OF COMPARATIVE ANATOMY 151

to nature, and through his great industry he became an in-
dependent observer. Here he laid the foundation of his ex-
tensive knowledge of comparative anatomy, and from this
quiet spot he sent forth his earliest scientific writings, which
served to carry his name to Paris, the great center of scien-
tific research in France,

Goes to Paris. — His removal from these provincial sur-
roundings v.as mainly owing to the warm support of Tessier,
who was spending the time of the reign of terror in retirement
in an adjacent village, under an assumed name. He and
Cu\'ier met in a scientific society, where the identity of Tessier
was discovered by Cuvier on account of his ease of speech
and his great familiarity with the topics discussed. A friend-
ship sprung up between them, and Tessier addressed some
of his scientific friends in Paris in the interest of Cuvier.
By this powerful introduction, and also through the inter-
vention of Geoffroy Saint-Hilaire, he came to Paris in 1 795
and was welcomed into the group of working naturalists
at the Jardin des Plantes, little dreaming at the time that
he should be the leader of the group of men gathered around
this scientific institution. He was modest, and so uncertain
of his future that for a year he held to his post of instructor,
bringing his young charge with him to Paris.

Notwithstanding the doubt which he entertained regard-
ing his abilities, his career proved successful from the begin-
ning. In Paris he entered upon a brilliant career, which was
a succession of triumphs. His unmistakable talent, com-
bined with industry and unusual opportunities, brought him
rapidly to the front. The large amount of material already
coll ec':ed, and the stimulating companionship of other scien-
tific workers, afforded an environment in which he grew
rapidly. He responded to the stimulus, and developed not
only into a great naturalist, but expanded into a finished
gentleman of the world. Circumstances shaped themselves

152 BIOLOGY AND ITS MAKERS

SO that he was called to occupy prominent offices under the
government, and he came uhimately to be the head of the
group of scientific men into which he had been welcomed as
a young man from the provinces.

His Physiognomy.— It is ver}^ interesting to note in his
portraits the change in his physiognomy accompanying his
transformation from a young man of provincial appearance

Fig. 41. — CuviER (1769-1832) as a Young Man.

into an elegant personage. Fig. 41 shows his portrait in the
early days when he was less mindful of his personal appear-
ance. It is the face of an eager, strong, youzig man, still re-
taining traces of his provincial life. His long, light-colored
hair is unkempt, but does not hide the magnificent propor-
tions of his head. Fig. 42 shows the growing refinement of
features which came with his advancement, and the aristo-
cratic look of supremacy which set upon his countenance after

RISE OF COMPARATIVE ANATOMY

^53

his wide recognition passing by a gradation of steps from the
position of head of the educational system, to that of baron
and peer of France.

Cuvier was a man of commanding power and colosal

Fig. 42. — Cuvier at the Zenith of His Power.

attainments ; he was a favorite of Napoleon Bonaparte, who
elevated him to office and made him director of the higher
educational institutions of the Empire. But to whatever
place of prominence he attained in the government, he never

154 BIOLOGY AND ITS MAKERS

lost his love for natural science. With him this was an
absorbing passion, and it may be said that he ranks higher
as a zoologist than as a legislator.

Comprehensiveness of Mind. — Soon after his arrival in
Paris he began to lecture upon comparative anatomy and to
continue work in a most comprehensive way upon the subjects
which he had cultivated at Caen. He saw ever}^thing on a
large scale. This led to his making extensive studies of what-
ever problems engaged his mind, and his studies were com-
bined in such a manner as to give a broad view of the subject.

Indeed, comprehensiveness of mind seems to have been
the characteristic which most impressed those who were
acquainted with him. Flourens says of him: " Ce qui ca-
racterise pariout M. Cuvier, c'est V esprit vaster His broad
and comprehensive mind enabled him to map out on great
lines the subject of comparative anatomy. His breadth was
at times his undoing, for it must be confessed that when the
details of the subject are considered, he was often inaccurate.
This was possibly owing to the conditions under which he
worked; having his mind diverted into many other chan-
nels, never neglecting his state duties, it is reasonable to
suppose that he lacked the necessary time to prove his ob-
servations in anatomy, and we may in this way account for
some of his inaccuracies.

Besides being at fault in some of his comparative anat-
omy, he adhered to a number of ideas that served to retard
the progress of science. He v/as opposed to the ideas of his
contemporary Lamarck, on the evolution of animals. He
is remembered as the author of the dogma of catastrophism
in geology. He adhered to the old notion of the pre-forma-
tion of the embryo, and also to the theory of the sponta-
neous origin of life.

Founds Comparative Anatomy. — Regardless of this
qualification, he was a great and distinguished student, and

RISE OF COMPARATIVE ANATOMY 1 55

founded comparative anatomy. From 1801 to 1805 appeared
his Legons cTAnatomie Comparec, a systematic treatise on the
comparative anatomy of animals, embracing both the in-
vertebrates and the vertebrates. In 181 2 was pubhshed his
great work on the fossil bones about Paris, an achievement
which founded the science of vertebrate palaeontology. His
extensive examination of the structure of fishes also added
to his already great reputation. His book on the animal
kingdom (Le Regne Animal distrihue d'apres son Organisa-
tion, 1816), in which he expounded his type-theory, has been
considered in a previous chapter.

He was also deeply interested in the historical develop-
ment of science, and his volumes on the rise of the natural
sciences give us almost the best historical estimate of the
progress of science that we have at the present day.

His Domestic Life. — Mrs. Lee, in a chatty account of
Cuvier, shows one of his methods of work. He had the
faculty of making others assist him in various ways. Not
only members of his family, but also guests in his household
were pressed into service. They were invited to examine
different editions of works and to indicate the differences in
the plates and in the text. This practice resulted in saving
much time for Cuvier, since in the preparation of his histor-
ical lectures he undertook to examine all the original sources
of the history with which he was engaged. In his lectures he
summarized facts relating to different editions of books, etc.

Mrs. Lee also gives a picture of his family life, which was,
to all accounts, very beautiful. He was devoted to his wife
and children, and in the midst of exacting cares he found
time to bind his family in love and devotion. Cuvier was
called upon to suffer poignant grief in the loss of his chil-
dren, and his direct family was not continued. He was
especially broken by the death of his daughter who had
grown to young womanhood and was about to be married.

15^ BIOLOGY AND ITS MAKERS

From the standpoint of a sincere admirer, Mrs. Lee
writes of his generosity and nobility of temperament, declar-
ing that his career demonstrated that his mind was great
and free from both envy and smallness.

Some Shortcomings. — Nevertheless, there are certain
things in the life of Cuvier that we wish might not have been.
His break with his old friends Lamarck and Saint-Hilaire
seems to show a domination of qualities that were not gen-
erous and kindly; those observations of Lamarck showing a
much profounder insight than any of which he himself was
the author were laughed to scorn. His famous controversy
with Saint-Hilaire marks a historical moment that will be
dealt with in the chapter on Rise of Evolutionary Thought.

George Bancroft, the American historian, met him during
a visit to Paris in 1827. He speaks of his magnificent eyes
and his fine appearance, but on the whole Cuvier seems to
have impressed Bancroft as a disagreeable man.

Some of his shortcomings that served to retard the prog-
ress of science have been mentioned. Still, with all his faults,
he dominated zoological science at the beginning of the nine-
teenth century, and so powerful was his influence and so un-
disputed was his authority among the French people that
the rising young men in natural science sided with Cuvier
even when he was wrong. It is a noteworthy fact that France,
under the influence of the traditions of Cuvier, was the last
country slowly and reluctantly to harbor as true the ideas
regarding the evolution of animal life.

Cuvier's Successors

While Cuvier's theoretical conclusions exercised a retard-
ing influence upon the progress of biology, his practical
studies more than compensated for this. It has been pointed
out how his type-theory led to the reform of the Linnaean

RISE OF COMPARATIVE ANATOMY

157

system, but, besides this, the stimulus which his investiga-
tions gave to studies in comparative anatomy was even of
more beneficent influence. As time passed the importance
of comparative anatomy as one division of biological science
impressed itself more and more upon naturalists. A large
number of investigators in France, England, and Germany
entered the field and took up the work where Cuvier had

Fig. 43. — H. Milne-Edwards, 1800-1885.

left it. The more notable of these successors of Cuvier
should come under consideration.

His intellectual heirs in France were Milne-Edwards and
Lacaze-Duthiers.

Milne-Edwards. — H. Milne-Edwards (1800-1885) was a
man of great industry and fine attainments ; prominent alike
in comparative anatomy, comparative physiology, and general
zoolog}', professor for many years at the Sorbonne in Paris.

158 BIOLOGY AND ITS MAKERS

In 1827 he introduced into biology the fruitful idea of the divi-
sion of physiological labor. He completed and published
excellent researches upon the structure and development of
many animals, notably Crustacea, corals, etc. His Vvork on
comparative anatomy took the form of explanations of the
activities of animals, or comparative physiology. His com-
prehensive treatise Legons sur la Physiologie et rAnaiomie
Comparee, in fourteen volumes, 185 7-1 881, is a mine of
information regarding comparative anatomy as v/ell as the
physiology of organisms.

Lacaze-Duthiers. — Henri de Lacaze-Duthiers (1821-
1901), the man of comprehensive mind, stimulating as an
instructor of young men, inspiring other workers, and pro-
ducing a large amount of original research on his own ac-
count, director of the Seaside Stations atRoscoff and Banyuls,
the founder of a noteworthy periodical of experimental zool-
ogy— this great man, whose portrait is shown in Fig. 44, was
one of the leading comparative anatomists in France.

R. Owen. — In England Richard Owen (1804-1892) carried
on the influence of Cuvier. At the age of twenty-seven he
went to Paris and renewed acquaintance with the great Cuvier,
whom he had met the previous year in England. He spent
some time at the Jardin des Plantes examining the extensive
collections in the museum. Although the idea was repudiated
by Owen and some of his friends, it is not unlikely that the
collections of fossil animals and the researches upon them
which engaged Cuvier at that time had great influence upon
the subsequent studies of Ow^en. Although he never studied
under Cuvier, in a sense he may be regarded as his disciple.
Owen introduced into anatomy the important conceptions
of analogy and homology, the former being a likeness based
upon the use to which organs are put, as the wing of a butter-
fly and the wing of a bat ; while homology is a true relation-
ship founded on likeness in structure and development, as

RISE OF COMPARATIVE ANATOMY

159

the wing of a bat and the foreleg of a dog. i\nalogy is a
superficial, and often a deceiving relationship; homology is
a true genetic relationship. It is obvious that this distinction

Fig. 44. — Lacaze-Duthiers, 1821-1901.

is of great importance in comparing the different parts of
animals. He made a large number of independent discov-
eries, and published a monumental work on the comparative

160

BIOLOGY AND ITS MAKERS

anatomy of vertebrates (1866-68). In much of his thought
he was singular, and many of his general conclusions have
not stood the test of time. He undertook to establish the
idea of an archtype in vertebrate anatomy. He clung to the
vertebral theory of the skull long after Huxley had shown such
a theory to be untenable. The idea that the skull is made up

Fig. 45. — Lorenzo Oken, 1779-1851

of modified vertebrae was propounded by Goethe and Oken.
In the hands of Oken it became one of the anatomical con-
clusions of the school of Naturphilosophie. This school of
transcendental philosophy was founded by Schelling, and
Oken (Fig. 45) was one of its typical representatives. The
vertebral theory of the skull was, therefore, not original
with Owen, but he adopted it, greatly elaborated it, and

RISE OF COMPARATIVE ANATOMY

i6l

clung to it blindly long after the foundations upon which it
rested were removed.

Richard Owen (Fig. 46) was succeeded by Huxley (1825-
1895), whose exactness of observation and rare judgment

Fig. 46. — Richard Owen, 1804-1892.

as to the main facts of comparative anatomy mark him as
one of the leaders in this field of research. The influence
of Huxley as a popular exponent of science is dealt with
in a later chapter.

l62 BIOLOGY AND ITS MAKERS

Meckel. — Just as Cuvier stands at the beginning of the
school of comparative anatomy in France, so does J. Fr.
Meckel in Germany. Meckel (i 781-1833) was a man of
rare talent, descended from a family of distinguished anat-
omists. From 1804 to 1806 he studied in Paris under Cuvier,
and when he came to leave the French capital to become
professor of anatomy at Halle, he carried into Germany the

Fig. 47. — J. Fr. Meckel, i 781-1833.

teachings and methods of his master. He was a strong force
in the university, attracting students to his department by
his excellent lectures and his ability to arouse enthusiasm.
Some of these students were stimulated to undertake re-
searches in anatomy, and there came from his laboratory a
number of investigations that were published in a periodical
which he founded. Meckel himself produced many scientific
papers and works on comparative anatomy, which assisted

RISE OF COMPARATIVE ANATOMY 163

materially in the advancement of that science. His portrait,
which is rare, is shown in Fig. 47.

Rathke. — Martin Henry Rathke (i 793-1860) greatly
advanced the science of comparative anatomy by insisting
upon the importance of elucidating anatomy with researches
in developmicnt. This is such an important consideration
that his influence upon the progress of comparative anatomy
can not be overlooked. After being a professor in Dorpat,
he came, in 1835, to occupy the position of professor of anat-
omy and zoology at Konigsberg, which had been vacated by
Von Bacr on the removal of the latter to St. Petersburg. His
writings are composed with great intelligence, and his facts
are carefully coordinated. Rathke belonged to the good old
school of German writers whose researches were profound
and extensive, and whose expression was clear, being based
upon matured thought. His papers on the aortic arches
and the Wolffian body are those most commonly referred to
at the present time.

Miiller. — Johannes Miiller (1801-1858), that phenomenal
man, besides securing recognition as the greatest physiol-
ogist of the nineteenth century, also gave attention to com-
parative anatomy, and earned the title of the greatest mor-
phologist of his time. His researches were so accurate, so
complete, so discerning, that his influence upon the develop-
ment of comparative anatomy was profound. Although he
is accorded, in history, the double distinction of being a great
anatomist and a great physiologist, his teaching tended to
physiology; and most of his distinguished students were
physiologists of the broadest type, uniting comparative anat-
om.y with their researches upon functional activities. (For
Miiller's portrait see p. 187.)

Gegenbaur. — In Karl Gegenbaur (i 826-1 903) scientific
anatomy reached its highest expression. His work was char-
acterized by broad and masterly analysis of the facts of strur-

l64 BIOLOGY AND ITS MAKERS

ture, to which were added the ideas derived from the study of
the development of organs. He was endowed with an intensely
keen insight, an insight which enabled him to separate from
the vast mass of facts the important and essential features,
so that they yielded results of great interest and of lasting im-
portance. This gifted anatomist attracted many young men

Fig. 48. — Karl Gegenbaur, 1826-1903.

from the United States and from other countries to pursue
under his direction the study of comparative anatomy. He
died in Heidelberg in 1903, where he had been for many years
professor of anatomy in the university.

In the group of living German anatomists the names of
Furbringer, Waldeyer, and Wiedersheim can not go unmen-
tioned.

RISE OF COMPARATIVE ANATOMY 105

E. D. Cope. — In America the greatest comparative
anatomist was E. D. Cope (1840-1897), a man of the highest
order of attainment, who dealt with the comparative anatomy
not only of living forms, but of fossil life, and made contribu-
tions of a permanent character to this great science; a man
whose title to distinction in the field of com.parative anatomy
will become clearer to later students with the passage of time.
For Cope's portrait see p. 336.

Of the successors of Cuvier, we would designate Meckel,
Owen, Gegenbaur, and Cope as the greatest.

Comparative anatomy is a very rich subject, and when
elucidated by embryology, is one of the firm foundations of
biology. If we regard anatomy as a science of statics, we
recognize that it should be united with physiology, which
represents the dynamical side of life. Comparative anatomy
and comparative physiology should go hand in hand in the
attempt to interpret living forms. Advances in these two
subjects embrace nearly all our knowledge of living organisms.
It is a cause for congratulation that comparative anatomy
has now become experimental, and that gratifying progress is
being made along the line of research designated as experi-
mental morphology. Already valuable results have been
attained in this field, and the outlook of experimental mor-
phology is most promising.

CHAPTER VIII
BICHAT AND THE BIRTH OF HISTOLOGY

We must recognize Bichat as one of the foremost men in
biological histoiy, although his name is not well known to the
general public, nor constantly referred to by biologists as
that of one of the chief luminaries of their science. In him
was combined extraordinary talent with powers of intense
and prolonged application; a combination which has always
produced notable results in the world. He died at the age
of thirty-one, but, within a productive period of not more
than seven years, he made observations and published work
that created an epoch and made a lasting impression on bio-
logical history.

His researches supplemented those of Cuvier, and carried
the analysis of animal organization to a deeper level. Cuvier
laid the foundations of comparative anatomy by dissecting
and arranging in a comprehensive system the organs of ani-
mals, but Bichat went a step further and made a profound
study of the tissues that unite to make up the organs. As we
have already noted in a previous chapter, this was a step in
reaching the conception of the real organization of living
beings.

Buckle's Estimate of Bichat. — It is interesting to note
the impression made by Bichat upon one of the greatest
students of the history of civilization. Buckle says of him:
''Great, however, as is the name of Cuvier, a greater still
remains behind. I allude, of course, to Bichat, whose repu-

166

THE BIRTH OF HISTOLOGY 167

tation is steadily advancing as our knowledge advances;
who, if we compare the shortness of his life with the reach and
depth of his views, must be pronounced the most profound
thinker and consummate observer by whom the organization
of the animal frame has yet been studied.

"We may except Aristotle, but between Aristotle and
Bichat I find no middle man."

Whether or not we agree fully with this panegyric of
Buckle, we must, I think, place Bichat among the most illus-
trious men of biological history, as Vesalius, J. Miiller, Von
Baer, and Balfour.

Marie Francois Xavier Bichat was born in 1771 at
Thoirette, department of the Ain. His father, who was a
physician, directed the early education of his son and had
the satisfaction of seeing him take kindly to intellectual pur-
suits. The young student was distinguished in Latin and
mathematics, and showed early a fondness for natural his-
tory. Having elected to follow the calling of his father, he
went to Lyons to study medicine, and came under the
instruction of Petit in surgery.

Bichat in Paris. — It was, on the whole, a fortunate cir-
cumstance for Bichat that the turbulent events of the French
Revolution drove him from Lyons to Paris, where he could
have the best training, the greatest stimulus for his growth,
and at the same time the widest field for the exercise of his
talents. We find him in Paris in 1793, studying under the
great surgeon Desault.

He attracted attention to himself in the class of this dis-
tinguished teacher and operator by an extemporaneous report
on one of the lectures. It was the custom in Desault's classes
to have the lectures of the professor reported upon before an
assistant by some student especially appointed for the pur-
pose. On one occasion the student who had been appointed
to prepare and deliver the review was absent, and Bichat,

l68 BIOLOGY AND ITS MAKERS

who was gifted v/ith a powerful memory, vohmteered without
previous notice to take his place. The lecture was a long and
difficult one on the fractures of the clavicle, but Bichat's
abstract was so clear, forceful, and complete that its delivery
in well-chosen language produced a great sensation both upon
the instructor and the students. This notable performance
served to bring him directly to the attention of Desault, who
invited him to become his assistant and to live in his family.
The association of Bichat with the great surgeon was most
happy. Desault treated him as a son, and when he suddenly
died in 1795, the care of preparing his works for the printer
was left to Bichat.

The fidelity with which Bichat executed this trust was
characteristic of his noble nature. He laid aside his own
personal interests, and his researches in which he was already
immersed, and by almost superhuman labor completed the
fourth volume of Desault's Journal oj Surgery and at the
same time collected and published his scattered papers. To
these he added observations of his ov/n, making alterations
to bring the work up to the highest plane. Thus he paid
the debt of gratitude which he felt he owed to Desault for
his friendship and assistance.

In 1797 he was appointed professor of anatomy, at the
age of twenty-six, and from then to the end of his life, in 1801,
he continued in his career of remarkable industry.

The portrait of this very attractive man is shown in
Fig. 49. His face shows strong intellectuality. He is de-
scribed as of " middling stature, with an agreeable face lighted
by piercing and expressive eyes." He was much beloved by
his students and associates, being "in all relations of life
most amiable, a stranger to envy or other hateful passions,
modest in demeanor and lively in his manners, which were
open and free."

His Phenomenal Industry. — His industry was phenom-

THE BIRTH OF HISTOLOGY 169

enal; besides doing the work of a professor, he attended to
a considerable practice, and during a single winter he is said
to have examined with care six hundred bodies in the pur-
suance of his researches upon pathological anatomy.

Fig. 49. — BicHAT, 1771-1801.

In the year 1800, when he was thirty years old, began to
appear the results of his matured researches. We speak of
these as being matured, not on account of his age or the great
number of years he had labored upon them, but from the

lyo BIOLOGY AND ITS MAKERS

intensity and completeness with which he had pursued his
investigations, thus giving to his work a lasting quality.

First came his treatise on the membranes {Traite des
Membranes)) followed quickly by his Physiological Re-
searches into the Phenomena of Life and Death (Recherches
Physiologiques sur la Vie et la Mort); then appeared his
General Anatomy {Anatomie Generak) in 1801, and his trea-
tise upon Descriptive Anatomy, upon which he was working
at the time of his death.

His death occurred in i8ci, and was due partly to an
accident. He slipped upon the stairs of the dissecting-room,
and his fall was followed by gastric derangement, from which
he died.

Results of His Work. — ^The new science of the anatomy
of the tissues which he founded is now known as histology,
and the general anatomy, as he called it, has now become
the study of minute anatomy of the tissues. Bichat studied
the membranes or tissues very profoundly, but he did not
employ the microscope and make sketches of their cellular
construction. The result of his work was to set the world
studying the minute structure of the tissues, a consequence
of which led to the modern study of histology. Since this
science was constructed directly upon his foundation, it is
proper to recognize him as the founder of histology.

Carpenter says of him : "Altogether Bichat left an impress
upon the science of life, the depth of which can scarcely be
overrated; and this not so much by the facts which he col-
lected and generalized, as by the method of inquiry which
he developed, and by the systematic form which he gave to
the study of general anatomy in its relations both to physi-
ology and pathology."

Bichat's More Notable Successors. — ^His influence ex-
tended far, and after the establishment of the cell-theory
took on a new phase. Microscopic study of the tissues has

THE BIRTH OF HISTOLOGY I?!

now become a separate division of the science of anatomy,
and engages the attention of a very large number of workers.
While the men who built upon Bichat's foundation are nu-
merous, we shall select for especial mention only a few of the
more notable, as Schwann, Koelliker, Schultze, Virchov/,
Leydig, and Ramon y Cajal, whose researches stand in the
direct Hne of development of the ideas promulgated by
Bichat.

Schwann. — Schwann's cell-theory was the result of close
attention to the microscopic structure of the tissues of ani-
mals. It was an extension of the knowledge of the tissues
which Bichat distinguished and so thoroughly investigated
from other points of view. The cell-theory, which took rise
in 1839, was itself epoch-making, and the science of general
anatomy was influenced by it as deeply as was the science of
embryology. The leading founder of this theory was
Theodor Schwann, whose portrait is shown on page 245,
where there is also a more extended account of his labors in
connection with the cell-theory. Had not the life of Bichat
been cut off in his early manhood, he might well have lived
to see this great discovery added to his own.

Koelliker. — ^Albrecht von Koelliker (181 7-1905) was one
of the greatest histologists of the nineteenth century. He is a
striking figure in the development of biology in a general way,
distinguished as an embryologist, as a histologist, and in
other connections. During his long life, from 181 7 to 1905,
he made an astounding number of additions to our knowledge
of microscopic anatomy. In the early years of his scientific
activity, ^'he helped in establishing the cell-theory, he traced
the origin of tissues from the segmenting ovum through the
developing embryo, he demonstrated the continuity between
nerve-fibers and nerve-cells of vertebrates (1845), • • • ^^^
much more." He is mentioned further, in connection with
the rise of embryology, in Chapter X.

172 BIOLOGY AND ITS MAKERS

The strong features of this veteran of research are shown
in the portrait, Fig. 50, which represents him at the age of
seventy.

In 1847 h^ was called to the University of Wiirzburg,
where he remained to the time of his death. From 1850 to
1900, scarcely a year passed without some important contri-
bution from Von Koelliker extending the knowledge of his-
tology. His famous text-book on the structure of the tissues
(Handbuch der Gewehelehre) passed through six editions from
1852 to 1893, the final edition of it being worked over and
brought up to date by this extraordinary man after he had
passed the age of seventy-five. By workers in biology this
will be recognized as a colossal task. In the second volume
of the last edition of this work, which appeared in 1893, he
went completely over the ground of the vast accumulation of
information regarding the nerv^ous system which an army of
gifted and energetic workers had produced. This was all
thoroughly digested, and his histological work brought down
to date.

Schultze. — The fine observations of Max Schultze (1825-
1874) may also be grouped with those of the histologists.
We shall have occasion to speak of him. more particularly in
the chapter on Protoplasm.. He did memorable ser\ace for
general biology in establishing the protoplasm doctrine, but
many of his scientific memoirs are in the line of normal
histology ; as, those on the structure of the olfactory mem-
brane, on the retina of the eye, the muscle elements, the
nerves, etc., etc.

Normal Histology and Pathology. — But histology has
two phases: the investigation of the tissues in health, which
is called normal histology; and the study of the tissues in
disease and under abnormal conditions of development,
which is designated pathological histology. The latter divi-
sion, on account of its importance to the medical man, has

Fig. 50. — Von Koelliker, 1817-1905.

174 BIOLOGY AND ITS MAKERS

been extensively cultivated, and the development of patho-
logical study has greatly extended the knowledge of the
tissues and has had its influence upon the progress of normal
histology. Goodsir, in England, and Henle, in Germany,
entered the lield of pathological histology, both doing work

Fig. 51. — Rudolph Virchow, 1821-1903.

of historical importance. They were soon followed b}- Vir-
chow, whose eminence as a man and a scientist has made
his name familiar to people in general.

Virchow. — Rudolph Virchow (1821-1903), for many
years a professor in the University of Berlin, was a notable
man in biological science and also as a member of the German

THE BIRTH OF HISTOLOGY 175

parliament. He assisted in molding the cell-theory into
better form, and in 1858 published a work on Cellular
Pathology, which applied the cell-theory to diseased tissues.
It is to be remembered that Bichat was a medical man, in-
tensely interested in pathological, or diseased, tissues, and we

Fig. 52. — Franz Leydig, 1821-1908.
Courtesy of Dr. Wm. M. Wheeler.

see in Virchow the one who especially extended Bichat's work
on the side of abnormal histology. Virchow's name is asso-
ciated also with the beginning of the idea of germinal conti-
nuity, which is the basis of Ijiological ideas regarding hered-
ity (see, further. Chapter XV).

Leydig. — Franz Leydig (Fig. 52) was early in the field
as a histologist with his handbook {Lehrhuch der Histologie

176

BIOLOGY AND ITS MAKERS

des Menschen mid der Thiere) published in 1857. He applied
histology especially to the tissues of insects in 1864 and sub-
sequent years, an account of which has already been given
in Chapter V.

Cajal as Histologist. — Ramon y Cajal, professor in the
University of Madrid, is a histologist whose work in a special

Fig, 53. — S. Ramon y Cajal, 1850-

field of research is of world-wide renown. His investigations
into the microscopic texture of the nervous system and sense-
organs have in large part cleared up the questions of the com-
plicated relations between the nervous elements. In com-
pany with other European investigators he visited the United
States in 1899 on the invitation of Clark University, where his
lectures were a feature of the celebration of the tenth anni-

THE BIRTH OF HISTOLOGY 177

versary of that university. Besides receiving many honors in
previous years, in 1906 he was awarded, in conjunction with
the Italian histologist Golgi, one of the Nobel prizes in recog-
nition of his notable investigations. Golgi invented the stain-
ing methods that Ramon y Cajal has applied so extensively
and so successfully to the histology of the nervous system.

These men in particular may be remembered as the inves-
tigators who expanded the work of Bichat on the tissues:
Schwann, for disclosing the microscopic elements of animal
tissues and founding the cell-theory; Koclliker, as the typical
histologist after the analysis of tissues into their elementary
parts; Virchow, as extending the cell-idea to abnormal his-
tology; Leydig, for applying histology to the lower animals ;
and Ramon y Cajal, for investigations into the histology of
the nervous system.

Text-Books of Histology. — ^Besides the works mentioned,
the text-books of Frey, Strieker, Ranvier, Klein, Schafer,
and others represent a period in the general introduction of
histology to students between 1859 and 1885. But these
excellent text-books have been largely superseded by the
more recent ones of Stohr, Boem-Davidoff, Piersol, Szy-
monowicz, and others. The number of living investigators
in histology is enormous; and their work in the subject of
cell-structure and in the department of embryology now
overlaps.

In pathological histology may be observed an illustration
of the application of biological studies to medicine. While
no attempt is made to give an account of these practical ap-
plications, they are of too great importance to go unmen-
tioned. Histological methods are in constant use in clinical
diagnosis, as in blood counts, the study of inflammations, of
the action of phagocytes, and of all manner of abnormal
growths.

In attempting to trace the beginning of a definite founda-

178 BIOLOGY AND ITS MAKERS

tion for the work on the structure of tissues, we go back to
Bichat rather than to Leeuwenhoek, as Richardson has pro-
posed. Bichat was the first to give a scientific basis for
histology founded on extensive observations, since all earlier
observers gave only separated accounts of the structure of
particular tissues.

CHAPTER IX

THE RISE OF PHYSIOLOGY
Harvey Haller Johannes Muller

Physiology had a parallel development with anatomy,
but for convenience it will be considered separately. Anatomy
shows us that animals and plants are wonderfully con-
structed, but after we understand their architecture and even
their minute structure, the questions remain, What are all
the organs and tissues for ? and what takes place within the
parts that are actually alive ? Physiology attempts to answer
questions of this nature. It stands, therefore, in contrast
with anatomy, and is supplementary to it. The activities of
living organisms are varied, and depend on life for their
manifestations. These manifestations may be called vital
activities. Physiology embraces a study of them all.

Physiology of the Ancients. — ^This subject began to at-
tract the attention of ancient medical men who wished to
fathom the activities of the body in order to heal its diseases,
but it is such a difficult thing to begin to comprehend the
activities of life that even the simpler relationships were im-
perfectly understood, and they resorted to mythical explana-
tions. They spoke of spirits and humors in the body as
causes of various changes; the arteries were supposed to
can-y air, the veins only blood ; and nothing was known of the
circulation. There arose among these early medical men
the idea that the body was dominated by a subtle spirit.
This went under the name pneuma, and the pneuma-theory
held sway until the period of the Revival of Learning.

179

l8o BIOLOGY AND ITS MAKERS

Among the ancient physiologists the great Roman phy-
sician Galen is the most noteworthy figure. As he was the
greatest anatomist, so he was also the greatest physiologist
of ancient times. All physiological knowledge of the time
centered in his wTitings, and these were the standards of
physiology for many centuries, as they were also for anatomy.
In the early days anatomy, physiology, and medicine were all
united into a poorly digested mass of facts and fancies. This
state of affairs lasted until the sixteenth century, and then the
awakening came, through the efforts of gifted men, endued
with the spirit of independent investigation. The advances
made depended upon the work or leadership of these men,
and there are certain periods of especial importance for the
advance of physiology that must be pointed out.

Period of Harvey. — ^The first of these epochs to be espe-
cially noted here is the period of Harvey (15 78- 165 7). In his
time the old idea of spirits and humors was giving way, but
there was still much vagueness regarding the activities of the
body. He helped to illuminate the subject by showing a con-
nection between arteries and veins, and by demonstrating
the circulation of the blood. As we have seen in an earlier
chapter, Harvey did not observe the blood passing through
the capillaries from arteries to veins, but his reasoning was
unassailable that such a connection must exist, and that the
blood made a complete circulation. He gave his conclusions
in his medical lectures as early as 1619, but did not publish
his views until 1628. It was reserved for Malpighi, in 1661,
actually to see the circulation through the capillaries under
the microscope, and for Leeuwenhoek, in 1669 and later
years, to extend these observations.

It was during Harvey's life that the microscope vras
brought into use and was of such great assistance in advanc-
ing knowledge. Harvey himself, however, made little use
of this instrument. It was during his life also that the knowl-

THE RISE OF PHYSIOLOGY l8l

edge of development was greatly promoted, first through his
own efforts, and later through those of Malpighi.

Harvey is to be recognized, then, as the father of modem
physiology. Indeed, before his time physiology as such can
hardly be spoken of as having come into existence. He intro-
duced experimental work into physiology, and thus laid the
foundation of modem investigation. It was the method of
Harvey that made definite progress in this line possible, and
accordingly we honor him as one of the greatest as well as
the earliest of physiologists.

Period of Haller.^From Harvey's time we pass to the
period of Haller (i 708-1 777), at the beginning of which
physiology was still wrapped up with medicine and anatomy.
The great work of Haller was to create an independent science
of physiology. He made it a subject to be studied for its
own sake, and not merely as an adjunct to medicine. Haller
was a man of vast and varied leaming, and to him was applied
by unsympathetic critics the title of " that abyss of leaming.'*
His portrait, as shown in Fig. 54, gives the impression of
a somewhat pompous and overbearing personality. He
was egotistical, self-complacent, and possessed of great
self-esteem. The assurance in the inerrancy of his own
conclusions was a marked characteristic of Haller's mind.
While he was a good observer, his own work showing con-
scientious care in observation, he was not a good interpreter,
and we are to recollect that he vigorously opposed the idea
of development set forth by Wolff, and we must also recog-
nize that his researches formed the chief starting-point of an
erroneous conception of vitality.

As Verwom points out, Haller's own experiments upon
the phenomena of irritability were exact, but they were
misinterpreted by his followers, and through the molding
influence of others the attempted explanation of their mean-
ing grew into the conception of a special vital force belong-

l82

BIOLOGY AND ITS MAKERS

ing to living organisms only. In its most complete form,
this idea provided for a distinct dualism between living and
lifeless matter, making all vital actions dependent upon the

Fig. 54. — Albrecht Haller, i 708-1 777.

operation of a mystical supernatural agency. This assump-
tion removed vital phenomena from the domain of clear
scientific analysis, and for a long time exercised a retarding
influence upon the progress of physiology.

THE RISE OF PHYSIOLOGY 183

His chief service of permanent value was that he brought
into one work all the facts and the chief theories of physiology
carefully arranged and digested. This, as has been said,
made physiology an independent branch of science, to be
pursued for itself and not merely as an adjunct to the study
of medicine. The work referred to is his Elements of Physi-
ology {Elementa Physiologice Corporis Humani, 1758), one
of the noteworthy books marking a distinct epoch in the
progress of science.

To the period of Haller also belongs the discovery of
oxygen, in 1774, by Priestley, a discovery which was destined
to have profound influence upon the subsequent development
of physiology, so that even now physiology consists largely
in tracing the way in which oxygen enters the body, the
manner in which it is distributed to the tissues, and the vari-
ous phases of vital activity that it brings about within the
living tissues.

Charles Bell.— The period of Haller may be considered
as extending beyond his lifetime and as terminating when the
influence of Muller began to be felt. Another discovery com-
ing in the closing years of Haller's period marks a capital
advance in physiology. I refer to the discovery of Charles
Bell (i 774-1842) showing that the nerve iibers of the anterior
roots of the spinal cord belong to the motor type, while those
of the posterior roots belong to the sensor)^ type.

This great truth was arrived at theoretically, rather than
as the result of experimental demonstration. It was first ex-
pounded by Bell in 181 1 in a small essay entitled Idea of a
New Anatomy of the Brain, which was printed for private
distribution. It was expanded in his papers, beginning in
1821, and published in the Philosophical Transactions of
the Royal Society of London, and finally embodied in his
work on the nervous system, published in 1830. At this
latter date Johannes Muller had reached the age of twenty-

1^4 BIOLOGY AND ITS MAKERS

nine, and had already entered upon his career as the lead-
ing physiologist of Germany. What Bell had divined he
demonstrated by experiments.

Charles Bell (Fig. 55) was a surgeon of eminence; in
private life he was distinguished by " unpretending amenity,
and simplicity of manners and deportment.''

Fig. 55. — Charles Bell, 1774-1842.

Period of Johannes Miiller. — The period that marks the
beginning of modern physiology came next, and was due to
the genius and force of Johannes Miiller (i 801-1858). Ver-
wom says of him: "He is one of those monumental fig-
ures that the history of every science brings forth but orxe.

THE RISE OF PHYSIOLOGY 185

They change the whole aspect of the field in which they work,
and all later growth is influenced by their labors." Johannes
MuUer was a man of very unusual talent and attainments,
the possessor of a master mind. Some have said, and not
without reason, that there was something supernatural about
Mliller, for his whole appearance bore the stamp of the un-
common. His portrait, with its massive head above the broad
shoulders, is shown in Fig. 56. In his lectures his manner
and his gestures reminded one of a Catholic priest. Early in
his life, before the disposition to devote himself to science
became so overwhelming, he thought of entering the priest-
hood, and there clung to him all his life some marks of
the holy profession. In his highly intellectual face we find
''a trace of severity in his mouth and compressed lips, with
the expression of most earnest thought on his brow and eyes,
and with the remembrance of a finished work in every
wrinkle of his countenance."

This extraordinary man exercised a profound influence
upon those who came into contact with him. He excited
almost unbounded enthusiasm and great veneration among
his students. They were allowed to work close by his side,
and so magnetic was his personality that he stimulated them
powerfully and succeeded in transmitting to them some
of his own mental qualities. As professor of physiology in
Berlin, MuUer trained many gifted young men, among whom
were Briicke (1819-1892), Du Bois-Reymond (1818-1896),
and Helmholtz (1821-1894), who became distinguished
scholars and professors in German universities. Helmholtz,
speaking of MuUer's influence on students, paid this tribute
to the grandeur of his teacher: "Whoever comes into contact
with men of the first rank has an altered scale of values in life.
Such intellectual contact is the most interesting event that
life can offer."

The particular service of Johannes Miiller to science was

l86 BIOLOGY AND ITS MAKERS

to make physiology broadly comparative. So comprehensive
was his grasp upon the subject that he gained for himself
the title of the greatest physiologist of modem times. He
brought together in his great work on the physiology of man
not only all that had been previously made known, carefully
sifted and digested, but a great mass of new information,
which was the result of his own investigations and of those
of his students. So rigorous were his scientific standards
that he did not admit into this treatise anything which had
been untested either by himself or by some of his assistants
or students. Verworn says of this monumental work, which
appeared in 1833, under the title Handbuch der Physiologie
des Menschen: "This work stands to-day unsurpassed in
the genuinely philosophical manner in which the material,
swollen to vast proportions by innumerable special researches,
was for the first time sifted and elaborated into a unitary
picture of the mechanism within the living organism. In this
respect the Handbuch is to-day not only unsurpassed, but
unequalled."

Miiller was the most accurate of observers; indeed, he is
the most conspicuous example in the nineteenth century of a
man who accomplished a prodigious amount of work all of
which was of the highest quality. In physiology he stood on
broader lines than had ever been used before. He employed
every means at his command — experimenting, the obser\^a-
tion of simple animals, the microscope, the discoveries in
physics, in chemistry, and in psychology.

He also introduced into physiology the pnnciples of psy-
chology, and it is from the period of Johannes Miiller that
we are to associate recognition of the close connection be-
tween the operations of the mind and the physiology of the
brain that has come to occupy such a conspicuous position
at the present time.

Miiller died in 1858, having reached the age of fifty -seven,

Fig. 56. — Johannes Muller, 1801-1858.

i^S BIOLOGY AND ITS MAKERS

but his influence was prolonged through the teachings of his
students.

Physiology after Muller.

Ludwig.— Among the men who handed on the torch of
Muller, Ludwig (Fig. 57) must be mentioned. Although

Fig. 57.— Ludwig, 1816-1895.

he was never a pupil of Muller, he gathered stimulus from
his writings and researches. For many years he lectured
in the University of Leipsic, attracting to that university
high-minded, eager, and gifted young men, who received

THE RISE OF PHYSIOLOGY

189

from this great luminary of physiology by expression what
he himself had derived from contact with Mtiller and his
writings. There are to-day distributed through the univer-
sities a number of young physiologists who stand only one

Fig. 58. — Du Bois-Reymond, 1818-1896.

generation removed from Johannes Miiller, and who still
labor in the spirit that was introduced into this depart-
ment of study by that great master.

Du Bois-Reymond. — Du Bois-Reymond (Fig. 58), an-
other of his distinguished pupils, came to occupy the chair

IQO BIOLOGY AND ITS MAKERS

which Mliller himself had filled in the University of Berlin,
and during the period of his vigor was in physiology one of
the lights of the world. It is no uncommon thing to find
recently published physiologies dedicated either to the mem-
ory of Johannes MuUer, as in the case of that remarkable
General Physiology by Verworn ; or to Ludwig, or to Du
Bois-Reymond, who were in part his intellectual product.
From this disposition among physiologists to do homage to
Miiller, we are able to estim^ate somewhat more closely the
tremendous reach of his influence.

Bernard. — ^When Miiller was twelve years old there was
born in Saint- Julien, department of the Rhone, Claude
Bernard, who attained an eminence as a physiologist, of which
the French nation are justly proud. Although he was little
thought of as a student, nevertheless after he came under the
influence of Magendie, at the age of twenty-six, he developed
rapidly and showed his true metal. He exhibited great
manual dexterity in performing experiments, and also a
luminous quality of mind in interpreting his observations.
One of his greatest achievements in physiology was the dis-
covery of the formation within the liver of glycogen, a sub-
stance chemically related to sugar. Later he discovered the
system of vaso-motor nerves that control and regulate the
caliber of the blood-vessels. Both of these discoveries as-
sisted materially in understanding the wonderful changes
that are going on within the human body. But besides his
technical researches, any special consideration of which lies
quite beyond the purpose of this book, he published in 1878-
1879 a work upon the phenomena of life in animals and
vegetables, a work that had general influence in extending
the knowledge of vital activities. I refer to his now classic
Legons sur les Phenomenes de la vie communs aux animaux et
aux vegetaux.

The thoughtful face of Bernard is shown in his portrait^

THE RISE OF PHYSIOLOGY 191

Fig. 59. He was one of those retiring, silent men whose
natures are difficult to fathom, and who are so frequently
misunderstood. A domestic infelicity, that led to the separa-
tion of himself from his family, added to his isolation and
loneliness. When touched by the social spirit he charmed

Fig. 59. — Claude Bernard, 1813-1878.

people by his personality. He was admired by the Emperor
Napoleon Third, through whose influence Bernard acquired
two fine laboratories. In 1868 he was elected to the
French Academy, and became thereby one of the "Forty
Immortals."

Foster describes him thus: "Tall in stature, with a fine

192 BIOLOGY AND ITS MAKERS

presence, with a noble head, the eyes full at once of thought
and kindness, he drew the look of observers upon him wher-
ever he appeared. As he walked in the streets passers-by
might be heard to say ' I wonder who that is ; he must be
some distinguished man.' "

Two Directions of Growth. — Physiology, established on
the broad foundations of Muller, developed along two inde-
pendent pathways, the physical and the chemical. We find
a group of physiologists, among whom Weber, Ludwig,
Du Bois-Reymond, and Helmholtz were noteworthy leaders,
devoted to the investigations of physiological facts through
the application of measurements and records made by ma-
chinery. With these men came into use the time-markers, the
myographs, and the ingenious methods of recording blood-
pressure, changes in respiration, the responses of muscle and
nerve to various forms of stimulation, the rate of transmission
of nerve-currents, etc.

The investigation of vital activities by means of measure-
ments and instrumental records has come to represent one
especial phase of modern physiolog}' . As might have been
predicted, the discoveries and extensions of knowledge re-
sulting from this kind of experimentation have been remark-
able, since it is obvious that permanent records made by
mechanical devices will rule out many errors; and, moreover,
they afford an opportunity to study at leisure phenomena
that occupy a very brief time.

The other marked line of physiological investigation has
been in the domain of chemistry, where Wohler, Liebig,
Kuhne, and others have, through the study of the chemical
changes occurring in its body, observed the various activities
that take place within the organism. They have reduced all
tissues and all parts of the body to chemical analysis, studied
the chemical changes in digestion, in respiration, etc. The
more recent observ^ers have also made a particular feature of

THE RISE OF PHYSIOLOGY 193

the study of the chemical changes going on within the living
matter.

The union of these two chief tendencies into the physico-
chemical aspects of physiology has established the modem
way of looking upon vital activities. These vital activi-
ties are now regarded as being, in their ultimate analysis,
due to physical and chemical changes taking place within the
living substratum. All along, this physico-chemical idea has
been in contest with that of a duality between the body and
the life that is manifested in it. The vitalists, then, have had
many controversies with those who make their interpretations
along physico-chemical lines. We will recollect that vitalism
in the hands of the immediate successors of Haller became
not only highly speculative, but highly mystical, tending to
obscure any close analysis of vital activity and throwing
explanations all back into the domain of mysticism. Johannes
Miiller was also a vitalist, but his vitalism was of a more
acceptable form. He thought of changes in the body as
being due to vitality — to a living force; but he did not deny
the possibility of the transformation of this vital energy into
other forms of energy ; and upon the basis of Miiller's work
there has been built up the modem conception that there is
found in the human body a particular transformation-form
of energy, not a mystical vital force that presides over all
manifestations of life.

The advances in physiology, beginning with those of
William Harvey, have had immense influence not only upon
medicine, but upon all biology. We find now the successful
and happy union between physiology and morphology in the
work which is being so assiduously carried on to-day under
the title of experimental morphology.

The great names in physiology since Muller are numerous,
and perhaps it is invidious to mention particular ones; but,
inasmuch as Ludwig and Du Bois-Reymond have been
13

194 BIOLOGY AND ITS MAKERS

spoken of, we may associate with them the names of Sir
Michael Foster and Burdon- Sanderson, in England ; and of
Briicke (one of Muller's disciples) and Verworn, in Ger-
many, as modern leaders whose investigations have pro-
moted advance, and whose clear exposition of the facts and
the theories of physiology have added much to the dignity
of the science.

CHAPTER X

VON BAER AND THE RISE OF EMBRYOLOGY

Anatomy investigates the arrangement of organic tissues ;
embryology, or the science of development, shows how they
are produced and arranged. There is no more fascinating
division of biological study. As Minot says: "Indeed, the
stories which embryology has to tell are the most romantic
known to us, and the wildest imaginative creations of Scott
or Dumas are less startling than the innumerable and almost
incredible shifts of role and change of character which
embryology has to entertain us with in her histories."

Embiyology is one of the most important biological sci-
ences in furnishing clues to the past history of animals.
Every organism above the very lowest, no matter how com-
plex, begins its existence as a single microscopic cell, and
between that simple state and the fully formed condition
every gradation of structure is exhibited. Every time an
animal is developed these constructive changes are repeated
in orderly sequence, and one who studies the series of steps
in development is led to recognize that the process of
building an animal's body is one of the most wonderful
in all nature.

Rudimentary Organs.— But, strangely enough, the course
of development in any higher organism is not straightforward,
but devious. Instead of organs being produced in the most
direct manner, unexpected by-paths are followed, as when
all higher animals acquire gill-clefts and many other rudi-

195

19^ BIOLOGY AND ITS MAKERS

mentary organs not adapted to their condition of life. Most
of the rudimentary organs are transitory, and bear testimony,
as hereditary survivals, to the line of ancestry. They are
clues by means of which phases in the evolution of animal
life may be deciphered.

Bearing in mind the continually shifting changes through
which animals pass in their embryonic development, one
begins to see why the adult structures of animals are so diffi-
cult to understand. They are not only complex ; they are also
greatly modified. The adult condition of any organ or tissue
is the last step in a series of gradually acquired modifications,
and is, therefore, the farthest departure from that which is
ancestral and archetypal. But in the process of formation
all the simpler conditions are exhibited. If, therefore, we
wish to understand an organ or an animal, we must follow its
development, and see it in simpler conditions, before the
great modifications have been added.

The tracing of the stages whereby cells merge into tissues,
tissues into organs, and determining how the organs by com-
binations build up the body, is embryology. On account of
the extended applications of this subject in biology, and the
light which it throws on all structural studies, we shall be
justified in giving its history at somewhat greater length
than that adopted in treating of other topics.

Five Historical Periods. — The story of the rise of this
interesting department of biology can, for convenience, be
divided into five periods, each marked by an advance in
general knowledge. These are: (i) the period of Harvey
and Malpighi; (2) the period of Wolff; (3) the period of
Von Baer; (4) the period from Von Baer to Balfour; and
(5) the period of Balfour, with an indication of present tend-
encies. Among all the leaders Von Baer stands as a monu-
mental figure at the parting of the ways between the new
and the old — the sane thinker, the great observer.

THE RISE OF EMBRYOLOGY 197

The Period of Harvey and Malpighi

In General.— The usual account of the rise of embryol-
ogy is derived from German writers. But there is reason to
depart from their traditions, in which Wolff is heralded as its
founder, and the one central figure prior to Pander and
Von Baer.

The embryological work of Wolff's great predecessors,
Harv^ey and Malpighi, has been passed over too lightly.
Although these men have received ample recognition in
closely related fields of investigation, their insight into those
mysterious events that culminate in the formation of a new
animal has been rarely appreciated. Now and then a few
writers, as Brooks and Whitman, have pointed out the great
worth of Harvey's work in embryology, but fewer have
spoken for Malpighi in this connection. Koelliker, it is true,
in his address at the unveiling of the statue of Malpighi, in
his native town of Crevalcuore, in 1894, gives him well-
merited recognition as the founder of embryology, and the
late Sir Michael Foster has written in a similar vein in his
delightful Lectures on the History oj Physiology.

However great was Harvey's work in embryology, I ven-
ture to say that Maipighi's was greater when considered as a
piece of observation. Harvey's v/ork is more philosophical;
he discusses the nature of development, and shows unusual
powers as an accurate reasoner. But that part of his treatise
devoted to observation is far less extensive and exact than
Maipighi's, and throughout his lengthy discussions he has
the flavor of the ancients.

Maipighi's work, on the contrary, flavors more of the
modems. In terse descriptions, and with many sketches, he
shows the changes in the hen's egg from the close of the first
day of development onward.

It is a noteworthy fact that, at the period in which he

19^ BIOLOGY AND ITS MAKERS

lived, Malpighi could so successfully curb the tendency to
indulge in wordy disquisitions, and that he was satisfied to
observe carefully, and tell his story in a simple way. This
quality of mind is rare. As Emerson has said: "I am im-
pressed with the fact that the greatest thing a human soul
ever does in this world is to see something, and tell what it
saw in a plain way. Hundreds of people can talk for one
who can think, but thousands can think for one who can see.
To see clearly is poetry, philosophy, and religion all in one."
But ''to see " here means, of course, to interpret as well as
to observe.

Although there were observers in the field of embryology
before Harvey, little of substantial value had been produced.
The earliest attempts were vague and uncritical, embracing
only fragmentary views of the more obvious features of body-
formation. Nor, indeed, should we look for much advance
in the field of embryology even in Harvey's time. The reason
for this w^ill become obvious when we remember that the
renewal of independent observation had just been brought
about in the preceding century by Vesalius, and that Harvey
himself was one of the pioneers in the intellectual awakening.
Studies on the development of the body are specialized,
involving observations on minute structures and recondite
processes, and must, therefore, wait upon considerable ad-
vances in anatomy and physiology. Accordingly, the science
of embryology was of late development.

Harvey. — Harvey's was the first attempt to make a criti-
cal analysis of the process of development, and that he did not
attain more was not owing to limitations of his powers of dis-
cernment, but to the necessity of building on the general level
of the science of his time, and, further, to his lack of instru-
ments of observation and technique. Nevertheless, Harvey
may be considered as having made the first independent
advance in embryology.

THE RISE OF EMBRYOLOGY 199

By clearly teaching, on the basis of his own observations,
the gradual formation of the body by aggregation of its parts,
he anticipated Wolff. This doctrine came to be known under
the title of "epigenesis," but Harv^ey's epigenesis* was not,
as Wolff's was, directed against a theory of pre-delineation of
the parts of the embryo, but against the ideas of the medical
men of the time regarding the metamorphosis of germinal
elements. It lacked, therefore, the dramatic setting which
surrounded the work of Wolff in the next century. Had the
doctrine of pre-formation been current in Harvey's time, we
are quite justified in assuming that he would have assailed it
as vigorously as did Wolff.

His Treatise on Generation.— Harvey's embiyological
work was published in 1651 under the title Exercitationes de
Generaiione Animalium. It embraces not only observations
on the development of the chick, but also on the deer and some
other mammals. As he was the court physician of Charles I,
that sovereign had many deer killed in the park, at interv^als,
in order to give Harvey the opportunity to study their devel-
opment.

As fruits of his observation on the chick, he showed the
position in which the embryo arises within the egg, viz., in
the white opaque spot or cicatricula; and he also corrected
Aristotle, Fabricius, and his other predecessors in many par-
ticulars.

Harvey's greatest predecessor in this field, Fabricius, was
also his teacher. When, in search of the best training in
medicine, Harvey took his way from England to Italy, as
already recounted, he came under the instruction of Fa-
bricius in Padua. In 160c, Fabricius published sketches
showing the development of animals; and, again, in 1625,
six years after his death, appeared his illustrated treatise on

* As Whitman has pointed out, Aristotle taught epigenesis as clearly as
Harvey, and is, therefore, to be regarded as the founder of that conception.

200 BIOLOGY AND ITS MAKERS

the development of the chick. Except the figures of Coiter
(1573), those of Fabricius were the earliest published illus-
trations of the kind. Altogether his figures show develop-
mental stages of the cow, sheep, pig, galeus, serpent, rat, and
chick.

Harvey's own treatise was not illustrated. With that
singular independence of mind for which he was conspicuous,
the vision of the pupil was not hampered by the authority of
his teacher, and, trusting only to his own sure observation
and reason, he described the stages of development as he
saw them in the egg, and placed his own construction on
the facts.

One of the earliest activities to arrest his attention in the
chick was a pulsating point, the heart, and, from this observa-
tion, he supposed that the heart and the blood were the first
formations. He says: "But as soon as the egg, under the
influence of the gentle warmth of the incubating hen, or of
warmth derived from another source, begins to pullulate,
this spot forthwith dilates, and expands like the pupil of the
eye; and from thence, as the grand center of the egg, the
latent plastic force breaks forth and germinates. This first
commencement of the chick, however, so far as I am aware,,
has not yet been observed by any one."

It is to be understood, however, that the descriptive part
of his treatise is relatively brief (about 40 pages out of 350 in
Willis's translation), and that the bulk of the 106 '' exercises "
into which his work is divided is devoted to comments on the
older writers and to discussions of the nature of the process
of development.

The aphorism, " omne vivum ex ovo,''' though not invented
by Harvey, was brought into general use through his wTitings.
As used in his day, however, it did not have its full modern
significance. With Harvey it meant simply that the embr}^os
of all animals, the viviparous as well as the oviparous, orig-

Fig. 6o. — Frontispiece to Harvey's Generatione Animalium (165 1).

202 BIOLOGY AND ITS MAKERS

nate in eggs, and it was directed against certain contrary
medical theories of the time.

The first edition of his Generatione Animalium, London,
1 65 1, is provided with an allegorical frontispiece embodying
this idea. As shown in Fig. 60, it represents Jove on a
pedestal, uncovering a round box, or ovum, bearing the
inscription ^' ex ovo omnia,''^ and from the box issue all forms
of living creatures, including also man.

Malpighi. — ^The observer in embryology who looms into
prominence between Harvey and Wolff is Malpighi. He
supplied what was greatly needed at the time — an illustrated
account of the actual stages in the development of the chick
from the end of the first day to hatching, shorn of verbose
references and speculations.

His observations on development are in two separate
memoirs, both sent to the Royal Society in 1672, and pub-
lished by the Society in Latin, under the titles De Formatione
Pulli in Ovo and De Ovo Incuhato. The two taken together
are illustrated by twelve plates containing eighty-six figures,
and the twenty-two quarto pages of text are nearly all devoted
to descriptions, a marked contrast to the 350 pages of Harvey
unprovided with illustrations.

His pictures, although not correct in all particulars, repre-
sent what he was able to see, and are very^ remarkable for
the age in which they were made, and considering the instru-
ments of observation at his command. They show successive
stages from the time the embryo is first outlined, and, taken
in their entirety, they cover a wide range of stages.

His observations on the development of the heart, com-
prising twenty figures, are the most complete. He clearly
illustrates the aortic arches, those transitory structures of
such great interest as showing a phase in ancestral history.

He was also the first to show by pictures the formation of
the head-fold and the neural groove, as well as the brain-

Fig. 6i. — Selected Sketches from Malpighi's Works, Showing
Stages in the Development of the Chick (1672).

204

BIOLOGY AND ITS MAKERS

vesicles and eye-pockets. His delineation of heart, brain,
and eye-vesicles are far ahead of those illustrating Wolff's
Tlieoria Generationis, made nearly a hundred years later.

Fig. 6i shows a few selected sketches from the various
plates of his embryological treatises, to compare with those of
Wolff. (See Fig. 63.)

The original drawings for De Ovo Inctibato, still in pos-
session of the Royal Society, are made in pencil and red chalk,

Fig. 62. — Marcello Malpighi, 1628--1694.

and an examination of them shows that they far surpass the
reproductions in finish and accuracy.

While Harvey taught the gradual formation of parts,
Malpighi, from his own observations, supposed the rudiments

THE RISE OF EMBRYOLOGY 205

of the embryo to pre-exist within the egg. He thought that,
possibly, the blood-vessels were in the form of tubes, closely
Avrapped together, which by becoming filled with blood were
distended. Nevertheless, in the treatises mentioned above
he is very temperate in his expressions on the whole matter,
and evidently believed in the new formation of many parts.

The portrait of Malpighi shown in Fig. 62 is taken from
his life by Atti. From descriptions of his personal appear-
ance (see page 58) one would think that this is probably a
better likeness than the strikingly handsome portrait painted
by Tabor, and presented by Malpighi to the Royal Society
of London. For a reproduction of the latter see page 59.

Malpighi*s Rank. — On the whole, Malpighi should rank
above Harvey as an embryologist, on account of his dis-
coveries and fuller representation, by drawings and descrip-
tions, of the process of development. As Sir Michael Foster
has said: "The first adequate description of the long series
of changes by which, as they melt the one into the other,
like dissolving views, the little white opaque spot in the egg
is transformed into the feathered, living, active bird, was
given by Malpighi. And where he left it, so for the most
part the matter remained until even the present century.
For this reason we may speak of him as the founder of
embryology."

The Period of Wolff

Between Harvey and Wolff, embryology had become
dominated by the theory that the embryo exists already
pre-formed within the egg, and, as a result of the rise of this
new doctrine, the publications of Wolff had a different setting
from that of any of his predecessors. It is only fair to say
that to this circumstance is owing, in large part, the prom-
inence of his name in connection with the theory of epigenesis.

2o6, BIOLOGY AND ITS MAKERS

As we have already seen, Harvey, more than a century before
the publications of Wolff, had clearly taught that develop-
ment is a process of gradual becoming. Nevertheless, Wolff's
work, as opposed to the new theory, was very important.

While the facts fail to support the contention that he was
the founder of epigenesis, it is to be remembered that he has
claims in other directions to rank as the foremost student of
embryology prior to Von Baer.

As a preliminary to discussing Wolff's position, we should
bring under consideration the doctrine of pre-formation and
encasement.

Rise of the Theory of Pre-delineation. — The idea of pre-
formation in its first form is easily set forth. Just as when
we examine a seed we find within an embryo plantlet, so it
was supposed that the various forms of animal life existed
in miniature within the egg. The process of development
was supposed to consist of the expansion or unfolding of this
pre-formed embryo. The process was commonly illustrated
by reference to flower-buds. '^ Just as already in a small bud
all the parts of the flower, such as stamens and colored petals,
are enveloped by the green and still undeveloped sepals;
just as the parts grow in concealment and then suddenly
expand into a blossom, so also in the development of animals,
it was thought that the already present, small but transparent
parts grow, gradually expand, and become discernible."
(Hertwig.) From the feature of unfolding this was called
in the eighteenth century the theory of evolution, giving to
that term quite a different meaning from that attached to it
at the present time.

This theory, strange as it may seem to us now, was
founded on a basis of actual observation — not entirely on
speculation. Although it was a product of the seventeenth
century, from several printed accounts one is likely to gather
the impression that it arose in the eighteenth century, and that

THE RISE OF EMBRYOLOGY 207

Bonnet, Haller, and I^eibnitz were among its founders. This
implication is in part fostered by the circumstance that
Swammerdam's Bihlia Naiurcg, which contains the germ of
the theor}^, was not pubHshed until 1737 — more than half a
century after his death — although the obser^^ations for it were
completed before Malpighi's first paper on embryology was
published in 1672. While it is well to bear in mind that date
of publication, rather than date of observation, is accepted
as establishing the period of emergence of ideas, there were
other men, as Malpighi and Leeuwenhoek, contemporaries
of Swammerdam, who published in the seventeenth century
the basis for this theory.

Malpighi supposed (1672) the rudiment of the embryo to
pre-exist within the hen's egg, because he observed evidences
of organization in the unincubated egg. This was in the
heat of the Italian summer (in July and August, as he him-
self records), and Dareste suggests that the developmental
changes had gone forward to a considerable degree before
Malpighi opened the eggs. Be this as it may, the imperfec-
tion of his instruments and technique would have made it
very difficult to see anything definitely in stages under
twenty-four hours.

In reference to his obser^^ations, he says that in the unin-
cubated egg he saw a small embryo enclosed in a sac which
he subjected to the rays of the sun. "Frequently I opened
the sac with the point of a needle, so that the animals con-
tained within might be brought to the light, nevertheless to
no purpose; for the individuals were so jelly-like and so very
small that they were lacerated by a light stroke. Therefore,
it is right to confess that the beginnings of the chick pre-exist
in the egg, and have reached a higher development in no other
way than in the eggs of plants." (" Quare ptdli stamina in ovo
prcEexistere, altioremque originem nacta esse fateri convenit,
haud dispari ritu, ac in Plantarum ovis.")

2o8 BIOLOGY AND ITS MAKERS

Swammerdam (1637-1680) supplied a somewhat better
basis. He observed that the parts of the butterfly, and other
insects as well, are discernible in the chrysalis stage. Also,
on observing caterpillars just before going into the pupa
condition, he saw in outline the organs of the future stage,
and very naturally concluded that development consists of
an expansion of already formed parts.

A new feature was introduced through the discovery, by
Leeuwenhoek, about 1677,* of the fertilizing filaments of
eggs. Soon after, controversies began to arise as to whether
the embryo pre-existed in the sperm or in the egg. By
/ Leeuwenhoek, Hartsoeker, and others the egg was looked
upon as simply a nidus within which the sperm developed,
and they asserted that the future animal existed in miniature
in the sperm. These controversies gave rise to the schools
of the animalculists, who believed the sperm to be the animal
germ., and of the ovulists, who contended for the ovum in that
role.

It is interesting to follow the metaphysical speculations
which led to another aspect of the doctrine of pre-formation.
There were those, notably Swammerdam, Leibnitz, and
Bonnet, who did not hesitate to follow the idea to the logical
consequence that, if the animal germ exists pre-formed, one
generation after another must be encased within it. This
gave rise to the fanciful idea of encasement or embottement,
which was so greatly elaborated by Bonnet and, by Leibnitz,
applied to the development of the soul. Even Swammerdam
(who, by the way, though a masterly observer, was always
a poor generalizer) conceived of the germs of all forthcoming
generations as having been located in the common mother
Eve, all closely encased one within the other, like the boxes
of a Japanese juggler. The end of the human race was con-

* The discovery is also attributed to Harnm, a medical student, and to
Hartsoeker, who claimed priority in the discovery.

/'"'^^

f??

-#-^34^:^^,,

%f.^

*'

^Jonii^fjf,

fm^

M

Fig. 63. — Plate from Wollil'sTheoria Generationis (1759), Showing
Stages in the Development of the Chick.

2IO BIOLOGY AND ITS MAKERS

ceived of by him as a necessity, when the last germ of this
wonderful series had been unfolded.

His successors, in efforts to compute the number of
homunculi which must have been condensed in the ovary of
Eve, arrived at the amazing result of two hundred millions.

Work of Wolff. — Friedrich Kaspar Wolff, as a young
man of twenty-six years, set himself against this grotesque
doctrine of pre-formation and encasement in his Theoria
Generationis, published in 1759. This consists of three
parts : one devoted to the development of plants, one to the
development of animals, and one to theoretical considera-
tions. He contended that the organs of animals make their
appearance gradually, and that he could actually follow their
successive stages of formation.

The figures in it illustrating the development of the chick,
some of which are shown in Fig. 63, are not, on the whole,
so good as Malpighi's. Wolff gives, in all, seventeen figures,
while Malpighi published eighty-six, and his twenty figures
on the development of the heart are more detailed than any
of Wolff's. When the figures represent similar stages of
development, a comparison of the two men's work is favor-
able to Malpighi. The latter shows much better, in corre-
sponding stages, the series of cerebral vesicles and their rela-
tion to the optic vesicles. Moreover, in the wider range of
his work, he shows many things — such as the formation of
the neural groove, etc. — not included in Wolff's observations.
Wolff, on the other hand, figures for the first time the prim-
itive kidneys, or "Wolffian bodies," of which he was the
discoverer.

Although Wolff was able to show that development con-
sists of a gradual formation of parts, his theory of develop-
ment was entirely mystical and unsatisfactory. The fruitful
idea of germinal continuity had not yet emerged, and the
thought that the egg has inherited an organization from

THE RISE OF EMBRYOLOGY 2II

the past was yet to be expressed. Wolff was, therefore, in
the same quandary as his predecessors when he undertook to
explain development. Since he assumed a total lack of
organization in the beginning, he was obliged to make devel-
opment '^miraculous " through the action on the egg of a
hyperphysical agent. From a total lack of organization, he
conceived of its being lifted to the highly organized product
through the action of a " vis essentialis corporis^

He returned to the problem of development later, and, in
1 768-1 769, published his best work in this field on the devel-
opment of the intestine.* This is a very original and strong
piece of observational work. While his investigations for the
Theoria Generationis did not reach the level of Malpighi's,
those of the paper of 1 768 surpassed them and held the posi-
tion of the best piece of embryological work up to that of
Pander and Von Baer. This work was so highly appreciated
by Von Baer that he said: ''It is the greatest masterpiece of
scientific observation v/hich we possess." In it he clearly
demonstrated that the development of the intestine and its
appendages is a true process of becoming. Still later, in
1789, he published further theoretical considerations.

Opposition to Wolff's Views. — But all W^olff's work was
launched into an uncongenial atmosphere. The great physi-
ologist Haller could not accept the idea of epigenesis, but
opposed it energetically, and so great was his authority that
the views of Wolff gained no currenc}^. This retarded
progress in the science of anmial development for more than
a half -century.

Bonnet was also a prolific writer in opposition to the ideas
of Wolff, and we should perhaps have a portrait of him
(Fig. 64) as one of the philosophical naturalists of the time.
His prominent connection with the theory of pre-delineation

* De Formatione Intestinorum, Nova Commentar, Ac. Sci. Petrop.,
St. Petersburg, XII., 1768; XIII., 1769.

212 BIOLOGY AND ITS MAKERS

in its less grotesque form, his discovery of the development
of the eggs of plant-lice without previous fertilization, his
researches on regeneration of parts in polyps and worms,
and other observations place him among the conspicuous

Fig. 64. — Charles Bonnet, 1720-1793.

naturalists of the period. His system of philosophy, which
has been carefully analyzed by Whitman, is designated by
that writer as a system of negations.

In 1 82 1, J. Fr. Meckel, recognizing the great value of

THE RISE OF EMBRYOLOGY 213

Wolff's researches on the development of the intestines,
rescued the work from neglect and obscurity by publishing
a German translation of the same, and bringing it to the
attention of scholars. From that time onward Wolff's labor
was fruitful.

His De Formatione Intestinorum rather than his Theoria
Generationis embodies his greatest contribution to embry-
ology. Not only is it a more fitting model of observation, but
in it he foreshadows the idea of germ-layers in the embryo,
which, under Pander and Von Baer, became the fundamental
conception in structural embryology. Throughout his re-
searches both early and late, he likens the embryonic rudiments,
which precede the formation of organs, to leaflets. In his
work of 1768 he described in detail how the leaf -like layers
give rise to the systems of organs ; showing that the nervous
system arises first from a leaf -like layer, and is followed,
successively, by a flesh layer, the vascular system, and lastly,
by the intestinal canal— all arising from original leaf-like
layers.

In these important generalizations, although they are
verbally incorrect, he reached the truth as nearly as it was
possible at the time, and laid the foundation of the germ-
layer theory.

Wolff was a man of great power as an obser/er, and al-
though his influence was for a long time retarded, he should
be recognized as the foremost investigator in embr}^olog}^
before Von Baer.

Few Biographical Facts. — The little known of his life
is gained through his correspondence and a letter by his
amanuensis. Through personal neglect, and hostility to his
work, he could not secure a foothold in the universities of
Germany, and, in 1764, on the invitation of Catherine of
Russia, he went to the Academy of Sciences at St. Petersburg,
where he spent the last thirty years of his life.

214 BIOLOGY AND ITS MAKERS

It has been impossible to discover a portrait of Wolff,
although I have sought one in various ways for several years.
The secretar}^ of the Academy of Sciences at St. Petersburg
writes that no portrait of Wolff exists there, and that the
Academy will gratefully receive information from any source
regarding the existence of a portrait of the great acade-
mician.

His sincere and generous spirit is shown in his correspond-
ence with Haller, his great opponent. " And as to the matter
of contention between us, I think thus: For me, no more
than for you, glorious man, is truth of the very greatest con-
cern. Whether it chance that organic bodies emerge from
an invisible into a visible condition, or form themselves out
of the air, there is no reason why I should wish the one were
truer than the other, or wish the one and not the other. And
this is your view also, glorious man. We are investigating
for truth only ; we seek that which is true. Why then should
I contend with you?" (Quoted from Wheeler.)

The Period of Von Baer

What Johannes MuUer was for physiology, von Baer
was for embryology; all subsequent growth was influenced
by his investigations.

The greatest classic in embryology is his Development of
Animals (Entwickelungsgeschichte der Tiere — Beohachtung
nnd Reflexion), the first part of which was published in 1828,
and the work on the second part completed in 1834, although
it was not published till 1837. This second part was never
finished according to the plan of Von Baer, but was issued by
his publisher, after vainly waiting for the finished manu-
script. The final portion, which Von Baer had withheld, in
order to perfect in some particulars, was published in 1888,
after his death, but in the form in which he left it in 1834.

THE RISE OF EMBRYOLOGY 215

The observations for the first part began in 1819, after he
had received a copy of Pander's researches, and covered a
period of seven years of close devotion to the subject; and
the observations for the last part were carried on at interv^als
for several years.

It is significant of the character of his Reflexionen that,
although published before the announcement of the cell-
theor}^, and before the acceptance of the doctrine of organic
evolution, they have exerted a molding influence upon
embryology to the present time. The position of von Baer
in embryology is owing as much to his sagacity in specula-
tion as to his powers as an observer. "Never again have
observation and thought been so successfully combined in
embryological work " (Minot).

Von Baer was bom in 1792, and lived on to 1876, but his
enduring fame in embryology rests on work completed more
than forty years before the end of his useful life. After his
removal from Konigsberg to St. Petersburg, in 1834, he very
largely devoted himself to anthropology in its widest sense,
and thereby extended his scientific reputation into other
fields.

If space permitted, it would be interesting to give the
biography* of this extraordinary man, but here it will be
necessary to content ourselves with an examination of his
portraits and a brief account of his work.

Portraits. — Several portraits of von Baer showing him
at different periods of his life have been published. A very
attractive one, taken in his early manhood, appeared in
Harper^ s Magazine for 1898. The expression of the face is
poetical, and the picture is interesting to compare with the
more matured, sage-like countenance forming the frontispiece

* Besides biographical sketches by Stieda, Waldeyer, and others, we have
a very entertaining autobiography of Von Baer, published in 1864, for pri-
vate circulation, but afterward (1866) reprinted and placed on sale.

2l0

BIOLOGY AND ITS MAKERS

of Stieda's Life of Von Baer (see Fig. 65). This, perhaps
the best of all his portraits, shows him in the full devel-
opment of his powers. An examination of it impresses one

Fig. 65. — Karl Ernst von Baer, 1792-1876.

with confidence in his balanced judgment and the thorough-
ness and profundity of his mental operations.

The portrait of Von Baer at about seventy years of age,

THE RISE OF EMBRYOLOGY 217

reproduced in Fig. 66, is, however, destined to be the one by
which he is commonly known to embryologists, since it forms
the frontispiece of the great cooperative Handbook oj Em-

FiG. 66. — ^VoN Baer at about Seventy Years of Age.

bryology just pubhshed under the editorship of Oskar
Hertwig.

Von Baer's Especial Service. — Apart from special dis-

2l8 BIOLOGY AND ITS MAKERS

coveries, Von Baer greatly enriched embr}^ology in three di-
rections : In the first place, he set a higher standard for all
work in embryology, and thereby lifted the entire science to
a higher level. Activity in a great field of this kind is, with
the rank and file of workers, so largely imitative that this
feature of his influence should not be overlooked. In the
second place, he established the germ-layer theory, and, in
the third, he made embryology comparative.

In reference to the germ-layer theory, it should be recalled
that Wolff had distinctly foreshadowed the idea by showing
that the material out of which the embryo is constructed is,
in an early stage of development, arranged in the form of
leaf-like layers. He showed specifically that the alimentary
canal is produced by one of these sheet-like expansions fold-
ing and rolling together.

Pander, by observations on the chick (1817), had ex-
tended the knowledge of these layers and elaborated the
conception of Wolff. He recognized the presence of three
primary layers — an outer, a middle, and an inner — out of
which the tissues of the body are formed.

The Germ-Layers.— But it remained for Von Baer,* by
extending his observ^ations into all the principal groups of
animals, to raise this conception to the rank of a general lav/
of development. He was able to show that in all animals

* It is of more than passing interest to remember that Pander and Von
Baer were associated as friends and fellow -students, under Dollinger at
Wiirzburg. It was partly through the influence of Von Baer that Pander
came to study with DoUinger, and took up investigations on development.
His ample private means made it possible for him to bear the expenses con-
nected with the investigation, and to secure the services of a fine artist for
making the illustrations. The result was a magnificently illustrated treatise.
His unillustrated thesis in Latin (1817) is more commonly known, but the
illustrated treatise in German is rarer. Von Baer did not take up his re-
searches seriously until Pander's were published. It is significant of their
continued harmonious relations that Von Baer's work is dedicated " An
meinen Jugendfreund, Dr. Christian Pander."

I

THE RISE OF EMBRYOLOGY 219

except the very lowest there arise in the course of devel-
opment leaf-like layers, which become converted into the
"fundamental organs" of the body.

Now, these elementary layers are not definitive tissues of
the body, but are embryonic, and therefore may appropriately
be designated "germ-layers." The conception that these
germ-layers are essentially similar in origin and fate in all
animals was a fuller and later development of the germ-layer
theory, a conception which dominated embryological study
until a recent date.

Von Baer recognized four such layers; the outer and inner
ones being formed first, and subsequently budding off a
middle layer composed of two sheets. A little later (1845)
Remak recognized the double middle layer of Von Baer as a
unit, and thus arrived at the fundamental conception of three
layers — the ecto-, endo-, and mesoderm — which has so long
held sway. For a long time after Von Baer the aim of em-
bryologists was to trace the history of these germ-layers, and
so in a wider and miuch qualified sense it is to-day.

It will ever stand to his credit, as a great achievement,
that Von Baer was able to make a very complicated feature
of development clear and relatively simple. Given a leaf -like
rudiment, with the layers held out by the yolk, as is the case
in the hen's egg, it was no easy matter to conceive how
they are transformed into the nerv^ous system, the body-wall,
the alimentary canal, and other parts, but Von Baer saw
deeply and clearly that the fundamental anatomical features
of the body are assumed by the leaf -like rudiments being
rolled into tubes.

Fig. 67 shows four sketches taken from the plates illus-
trating von Baer's work. At A is shown a stage in the forma-
tion of the embryonic envelope, or amnion, which surrounds
the embryos of all animals above the cla:ss of amphibia. Bj
another figure of an ideal section, shows that, long before the

220 BIOLOGY AND ITS MAKERS

day of microtomes, Von Baer made use of sections to represent
the relationships of his four germ-layers. At C and D is
represented diagrammatically the way in which these layers
are rolled into tubes. He showed that the central nervous
system arose in the form of a tube, from the outer layer ; the
body -wall in the form of a tube, composed of skin and muscle
layers; and the alimentary tube from mucous and vascular
layers.

The generalization that embryos in development tend to
recapitulate their ancestral history is frequently attributed to
Von Baer, but the qualified way in which he suggests some-
thing of the sort will not justify one in attaching this con-
clusion to his work.

Von Baer was the first to make embryology truly com-
parative, and to point out its great value in anatomy and
zoology. By embryological studies he recognized four types
of organization — as Cuvier had done from the standpoint of
comparative anatomy. But, since these types of organiza-
tion have been greatly changed and subdivided, the impor-
tance of the distinction has faded away. As a distinct break,
however, with the old idea of a linear scale of being it was
of moment.

Among his especially noteworthy discoveries may be
mentioned that of the egg of mammals (1827), and the noto-
chord as occurring in all vertebrate animals. His discovery
of the mammalian egg had been preceded by Purkinje's
observations upon the germinative spot in the bird's egg

(1825).

Von Baer*s Rank. — Von Baer has come to be dignified
with the title of the "father of modern embryology." No
man could have done more in his period, and it is owing to
his superb intellect, and to his talents as an observer, that he
accomplished what he did. As Minot says: "He worked
out, almost as fully as was possible at this time, the genesis

Fig. 67. — Sketches from Von Baer's Embryological Treatise (1828).

222 BIOLOGY AND ITS MAKERS

of all the principal organs from the germ-layers, instinctively
getting at the truth as only a great genius could have done."

After his masterly work, the science of embryology could
never return to its former level; he had given it a new direc-
tion, and through his influence a period of great activity was
introduced.

The Period from Von Baer to Balfour

In the period between Von Baer and Balfour there were
great general advances in the knowledge of organic structure
that brought the whole process of development into a new
light.

Among the most important advances are to be enumerated
the announcement of the cell-theory, the discovery of proto-
plasm, the beginning of the recognition of germinal continuity,
and the establishment of the doctrine of organic evolution.

The Cell-Theory. — ^The generalization that the tissues of
all animals and plants are structurally composed of similar
units, called cells, was given to the world through the com-
bined labors of Schleiden and Schwann. The history of this
doctrine, together with an account of its being remodeled
into the protoplasm doctrine, is given in Chapter XII.

The broad -reaching effects of the cell-theory may be easily
imagined, since it united all animals on the broad plane of
likeness in microscopic structure. Now for the first time
the tissues of the body were analyzed into their units ; now
for the first time was comprehended the nature of the germ-
layers of Von Baer.

Among the first questions to emerge in the light of the new
researches were concerning the origin of cells in the organs,
the tissues, and the germ-layers. The road to the investiga-
tion of these questions was already opened, and it was fol-
lowed, step by step, until the egg and the sperm came to be

THE RISE OF EMBRYOLOGY 223

recognized as modified cells. This position was reached,
for the egg, about 1861, when Gegenbaur showed that the
eggs of all vertebrate animals, regardless of size and con-
dition, are in reality single cells. The sperm was put in the
same category about 1865.

The rest was relatively easy: the egg, a single cell, by
successive divisions produces many cells, and the arrange-
ment of these into primary embryonic layers brings us to the
starting-point of Wolff and Von Baer. The cells, continuing
to multiply by division, not only increase in number, but also
undergo changes through division of physiological labor,
whereby certain groups are set apart to perform a particular
part of the work of the body. In this way arise the various
tissues of the body, which are, in reality, similar cells per-
forming a similar function. Finally, from combinations of
tissues, the organs are formed.

But the egg, before entering on the process of develop-
ment, must be stimulated by the union of the sperm with the
nucleus of the egg, and thus the starting-point of every animal
and plant, above the lowest group, proves to be a single cell
with protoplasm derived from two parents. While questipns
regarding the origin of cells in the body were being answered,
the foundation for the embr}^ological study of heredity was
also laid.

Advances were now more rapid and more sure; flashes of
morphological insight began to illuminate the way, and the
facts of isolated observations began to fit into a harmonized
whole.

Apart from the general advances of this period, men-
tioned in other connections, the work of a few individuals
requires notice.

Rathke and Remak wxre engaged with the broader aspects
of embryology, as well as with special investigations. From
Rathke's researches came great advances in the knowledge of

224 BIOLOGY AND ITS MAKERS

the development of insects and other invertebrates, and Remak
is notable for similar work with the vertebrates. As already
mentioned, he was the first to recognize the middle layer as
a unit, through which the three germ-layers of later embry-
ologists emerged into the literature of the subject.

Koelliker, i8i 7-1905, the veteran embryologist, for so
many years a professor in the University of Wiirzburg, carried
on investigations on the segmentation of the egg. Besides
work on the invertebrates, later he followed with care the
development of the chick and the rabbit; he encompassed
the whole field of embryology, and published, in 1861 and
again in 1876, a general treatise on vertebrate embryology,
of high merit. The portrait of this distinguished man is
shown in Chapter VIII, where also his services as a histologist
are recorded.

Huxley took a great step toward unifying the idea of germ-
layers throughout the animal kingdom, when he maintained,
in 1849, that the two cell-layers in animals like the hydra
and oceanic hydrozoa correspond to the ectoderm and
endoderm of higher animals.

Kow^alevsky (Fig. 68) made interesting discoveries of a
general bearing. In 1866 he showed the practical identity,
in the early stages of development, between one of the lowest
vertebrates (amphioxus) and a tunicate. The latter up to
that time had been considered an invertebrate, and the effect
of Kowalevsky's observations was to break down the sharply
limited line supposed to exist between the invertebrates and
the vertebrates. This was of great influence in subsequent
work. Kowalevsky also founded the generalization that all
animals in development pass through a gastrula stage — a
doctrine associated, since 1874, with the name of Haeckel
under the title of the gastraea theory.

Beginning of the Doctrine of Germinal Continuity. —
The conception that there is unbroken continuity of germinal

THE RISE OF EMBRYOLOGY 225

substance between all living organisms, and that the egg and
the sperm are endowed with an inherited organization of
great complexity, has become the basis for all current theories
of heredity and development. So much is involved in this
conception that, in the present decade, it has been designated
(Whitman) " the central fact of modem biology." The first
clear expression of it is found in Virchow's Cellular Pa-
thology, published in 1858. It was not, however, until the

Fig. 68. — A. Kowalevsky, 1840-1901.

period of Balfour, and through the work of Fol, Van Beneden
(chromosomes, 1883), Boveri, Hertwig, and others, that the
great importance of this conception began to be appreciated,
and came to be woven into the fundamental ideas of de-
velopment.

Influence of the Doctrine of Organic Evolution. — ^This

doctrine, although founded in its modern sense by Lamarck

in the early part of the nineteenth century, lay dormant until

Darwin, in 1859, brought a new feature into its discussion

15

226 BIOLOGY AND ITS MAKERS

by emphasizing the factor of natural selection. The general
acceptance of the doctrine, which followed after fierce oppo-
sition, had, of course, a profound influence on embryology.
The latter science is so intimately concerned with the gene-
alogy of animals and plants, that the newly accepted doc-
trine, as affording an explanation of this genealogy, was the
thing most needed.

The development of organisms was now seen in the light
of ancestral history, rudim_entary organs began to have
meaning as hereditary survivals, and the whole process of
development assumed a dift'erent aspect. This doctrine
supplied a new impulse to the interpretation of nature at
large, and of the embr^^ological record in particular. The
meaning of the embryological record was so greatly em-
phasized in the period of Balfour that it will be commented
upon under the next division of our subject.

The period between Von Baer and Balfour proved to be
one of great importance on account of the general advances
in knowledge of all organic nature. Observ^ations were
moving toward a better and more consistent conception of
the structure of animals and plants. A new comparative
anatomy, more profound and richer in meaning than Cu-
vier's, was arising. The edifice on the foundation of Von
Baer's work was now emerging into recognizable outlines.

The Period of Balfour, with an Indication of Present
Tendencies

Balfour's Masterly Work.— The workers of this period
inherited all the accumulations of previous efforts, and the
time was ripe for a new step. Observations on the develop-
ment of different animals, vertebrates and invertebrates, had
accumulated in great number, but they w^ere scattered
through technical periodicals, transactions of learned societies,

THE RISE OF EMBRYOLOGY

227

monographs, etc., and there was no compact science of em-
bryology with definite outlines. Balfour reviewed all this
mass of information, digested it, and molded it into an organ-
ized wliole. The results were published in the form of two
volumes with the title of Comparative Embryology. This
book of "almost priceless value" was given to the world in
1880-1881. It was a colossal undertaking, but Balfour was

Fig. 69. — Francis M. Balfour, 1851-1882.

a phenomenal worker. Before his untimely death at the age
of thirty-one, he had been able to complete this work and to
produce, besides, a large number of technical researches.
The period of Balfour is taken arbitrarily in this volume as
beginning about 1874, when he published, with Michael
Foster, The Elements of Embryology.

His University Career. — Balfour (Fig. 69) was bom in

228 BIOLOGY AND ITS MAKERS

1 85 1. During his days of preparation for the university he
was a good student, but did not exhibit in any marked way
the powers for which later he became distinguished. At
Cambridge, his distinguished teacher, the late Sir Michael
Foster, recognized his great talents, and encouraged him to
begin work in embryology. His labors in this field once
begun, he threw himself into it with great intensity. He rose
rapidly to a professorship in Cambridge, and so great was
his enthusiasm and earnestness as a lecturer that in seven
years " voluntaiy attendance on his classes advanced from
ten to ninety." He was also a stimulator of research, and at
the time of his death there were twenty students engaged in
his laboratory on problems of development.

He was distinguished for personal attractiveness, and
those who met him were impressed with his great sincerity,
as well as his personal charm. He was welcomed as an
addition to the select group of distinguished scientific men of
England, and a great career was predicted for him. Huxley,
when he felt the call, at a great personal sacrifice, to lay aside
the more rigorous pursuits of scientific research, and to devote
himself to molding science into the lives of the people, said
of Balfour: "He is the only man who can carry out my
work."

His Tragic Fate. — But that was not destined to be. The
story of his tragic end need be only referred to. After com-
pleting the prodigious labor on the Comparative Embry-
ology he went to Switzerland for recuperation, and met his
death, with that of his guide, by slipping from an Alpine
height into a chasm. His death occurred in July, 1882.

The memorial edition of his works fills four quarto vol-
umes, but the ''Comparative Embryology" is Balfour's
monument, and will give him enduring fame. It is not only
a digest of the work of others, but contains also general
considerations of a far-seeing quality. He saw develop-

THE RISE OF EMBRYOLOGY 229

mental processes in the light of the hypothesis of organic
evolution. His speculations were sufficiently reserved, and
nearly always luminous. It is significant of the character
of this work to say that the speculations contained in the
papers of the rank and file of embryological workers for more
than two decades, and often fondly believed to be novel,
were for the most part anticipated by Balfour, and were also
better expressed, with better qualifications.

The reading of ancestral history in the stages of develop-
ment is such a characteristic feature of the embryological
work of Balfour's period that some observ^ations concerning
it will now be in place.

Interpretation of the Embryological Record. — Perhaps
the most impressive feature of animal development is the
series of similar changes through which all pass in the embr}^o.
The higher animals, especially, exhibit all stages of organiza-
tion from the unicellular fertilized ovum to the fully formed
animal so far removed from it. The intermediate changes
constitute a long record, the possibility of interpreting which
has been a stimulus to its careful examination.

Meckel, in 182 1, and later Von Baer, indicated the close
similarity between embryonic stages of widely different
animals; Von Baer, indeed, confessed that he was unable to
distinguish positively between a reptile, a bird, and a mam-
malian embryo in certain early stages of growth.

In addition to this similarity, which is a constant feature of
the embryological record, there is another one that may be
equally significant ; viz., in the course of embryonic history,
sets of rudimentary organs arise and disappear. Rudiment-
ary teeth make their appearance in the embr}^'o of the wdiale-
bone whale, but they are transitory and soon disappear with-
out having been of service to the animal. In the embrj'os
of all higher vertebrates, as is well know^n, gill-clefts and
gill-arches with an appropriate circulation, make their ap-

230 BIOLOGY AND ITS MAKERS

pcarancc, but disappear long before birth. These indica-
tions, and similar ones, must have some meaning.

Now whatever qualities an animal exhibits after birth
are attributed to heredity. May it not be that all the inter-
mediate stages are also inheritances, and, therefore, represent
phases in ancestral history? If they be, indeed, clues to
ancestral conditions, m.ay we not, by patching together our
observations, be able to interpret the record, just as the his-
tory of ancient peoples has been made out from fragments
in the shape of coins, vases, implements, hieroglyphics, in-
scriptions, etc.?

The Recapitulation Theory. — The results of reflection in
this direction led to the foundation of the recapitulation
theory, according to which animals are supposed, in their
individual development, to recapitulate to a considerable
degree phases of their ancestral history. This is one of the
widest generalizations of embryology. It was suggested in
the writings of Von Baer and Louis Agassiz, but received its
first clear and complete expression in 1863, in the writings of
Fritz Muller.

Although the course of events in development is a record,
it is, at best, only a fragmentary and imperfect one. Many
stages have been dropped out, others are unduly prolonged
or abbreviated, or appear out of chronological order, and,
besides this, some of the structures have arisen from adapta-
tion of a particular organism to its conditions of develop-
ment, and are, therefore, not ancestral at all, but, as it were,
recent additions to the text. The interpretation becomes a
difficult task, which requires much balance of judgment and
profound analysis.

The recapitulation theory was a dominant note in all
Balfour's speculations, and in that of his contemporary and
fellow-student Marshall. It has received its most sweeping
application in the works of Ernst Haeckel.

THE RISE OF EMBRYOLOGY 23I

Widely spread throughout recent literature is to be noted
a reaction against the too wide and unreserved application
of this doctrine. This is naturally to be expected, since it
is the common tendency in all fields of scholarship to demand

Fig. 70. — OsKAR Hertwig in 1890.

a more critical estimate of results, and to undergo a reaction
from the earlier crude and sweeping conclusions.

Nearly all problems in anatomy and structural zoology
are approached from the embryological side, and, as a con-
sequence, the work of the great army of anatomists and

232 BIOLOGY AND ITS MAKERS

zoologists has been in a measure embryological. Many of
them have produced beautiful and important researches, but
the work is too extended to admit of review in this connection.

Oskar Hertwig, of Berlin (Fig. 70), is one of the repre-
sentative embryologists. of Europe, while, in this country,
lights of the first magnitude are Brooks, Minot, Whitman,
E. B. Wilson, and others.

Although no attempt is made to review the researches of
the xCcent period, we cannot pass entirely without mention
the discovery of chromosomes, and of their reduction in the
ripening of the egg and in the formation of sperm. This has
thrown a flood of light on the phenomena of fertilization, and
has led to the recognition of chromosomes as probably the
bearers of heredity. The nature of fertilization, investigated
by Fol, O. Hertwig, and others, formed the starting-point for
a series of brilliant discoveries.

The embryological investigations of the late Wilhelm His
(Fig. 71) are also deserving of especial notice. His luminous
researches on the development of the ners^ous system, the
origin of nerve fibers, and his analysis of the development of
the human embryo are all veiy important.

Recent Tendencies. Experimental Embryology. — Soon
after the publication of Balfour's great work on " Comparative
Embryology," a new tendency in research began to appear
which led onward to the establishment of experimental em-
brj'ology. All previous work in this field had been concerned
with the structure, or architecture, of organisms, but now the
physiological side began to receive attention. Whitman has
stated with great aptness the interdependence of these two
lines of work, as follows: " Morphology raises the question^
How came the organic mechanism into existence? Has it
had a history, reaching its present stage of perfection through
a long series of gradations, the first term of which w^as a
relatively simple stage ? The embryological history is traced

Fig. 71. — WiLHELM His, 1831-1904. At Sixty-four Years.

234 BIOLOGY AND ITS MAKERS

out, and the palaeontological records are searched, until the
evidence from both sources establishes the fact that the organ
or organism under study is but the summation of modifica-
tions and elaborations of a relatively simple primordial. This
point settled, physiology is called upon to complete the story.
Have the functions remained the same through the series?
or have they undergone a series of modifications, differentia-
tions, and improvements more or less parallel with the mor-
phological series?"

Since physiolog}^ is an experimental science, all questions
of this nature must be investigated with the help of experi-
ments. Organisms undergoing development have been sub-
jected to changed conditions, and their responses to various
forms of stimuli have been noted. In the rise of experimental
embryology we have one of the most promising of the recent
departures from the older aspects of the subject. The results
already attained in this attractive and suggestive field make
too long a story to justify its telling in this volume. Roux,
Herbst, Loeb, Morgan, E. B. Wilson, and many others have
contributed to the grov/th of this new division of embryology.
Good reasons have been adduced for believing that qualitative
changes take place in the protoplasm as development pro-
ceeds. And a curb has been put upon that ''great fault of
embryology, the tendency to explain any and every operation
of development as merely the result of inheritance." It has
been demonstrated that surrounding conditions have much
to do with individual development, and that the course of
events may depend largely upon stimuli coming from with-
out, and not exclusively on an inherited tendency.

Cell-Lineage. — Investigations on the structural side have
reached a high grade of perfection in studies on cell-lineage.
The theoretical conclusions in the germ-layer theory are
based upon the assumption of identity in origin of the differ-
ent layers. But the lack of agreement among observ^ers, espe-

THE RISE OF EMBRYOLOGY 235

cially in reference to the origin of the mesoderm, made it
necessary to study more closely the early developmental stages
before the establishment of the germ-layers. It is a great
triumph of exact observation that, although continually
changing, the consecutive history of the individual cells has
been followed from the beginning of segmentation to the time
v^^hen the germ-layers are established. Some of the beautifully
illustrated memoirs in this field are highly artistic.

Blochman (1882) was a pioneer in observations of this
kind, and, following him, a number of American investigators
have pursued studies on cell-lineage with great success.
The researches of Whitman, Wilson, Conklin, Kofoid, Lillie,
Mead, and Castle have given us the history of the origin of
the germ-layers, cell by cell, in a variety of animal forms.
These studies have shown that there is a lack of uniformity
in the origin of at least the middle layer, and therefore
there can be no strict homology of its derivatives. This
makes it apparent that the earlier generalizations of the
germ-layer theory were too sweeping, and, as a result, the
theory is retained in a much modified form.

Theoretical Discussions. — Certain theoretical discus-
sions, based on embryological studies, have been rife in recent
years. And it is to be recognized without question that dis-
cussions regarding heredity, regeneration, the nature of the
developmental process, the question of inherited organiza-
tion within the egg, of germinal continuity, etc., have done
much to advance the subject of embryolog}\

Embryology is one of the three great departments of
biology which, taken in combination, supply us with a knowl-
edge of living forms along lines of structure, function, and
development. The embiyological method of study is of in-
creasing importance to comparative anatomy and physiology.
Formerly it was entirely structural, but it is now becoming
also experimental, and it will therefore be of more service to

236 BIOLOGY AND ITS MAKERS

physiology. While it has a strictly technical side, the science
of embryology must always remain of interest to intelligent
people as embracing one of the most wonderful processes
in nature — the development of a complex organism from the
single-celled condition, with a panoramic representation of
all the intermediate stages.

CHAPTER XI

THE CELL THEORY— SCHLEIDEN, SCHWANN,
SCHULTZE

The recognition, in 1838, of the fact that all the various
tissues of animals and plants are constructed on a similar plan
wsis an important step in the rise of biology. It was progress
along the line of microscopical observation. One can readily
understand that the structural analysis of organisms could
not be completed until their elementaiy parts had been dis-
covered. When these units of structure were discovered
they were called cells — from a misconception of their nature —
and, although the misconception has long since been cor-
rected, they still retain this historical but misleading name.

The doctrine that all tissues of animals and plants are
composed of aggregations of these units, and the derivatives
from the same, is known as the cell-theory. It is a general-
ization which unites all animals and plants on the broad plane
of similitude of structure, and, when we consider it in the
light of its consequences, it stands out as one of the great
scientific achievements of the nineteenth century. There is
little danger of overestimating the importance of this doctrine
as tending to unify the knowledge of living organisms.

Vague Foreshado wings of the Cell-Theory. — In attempt-
ing to trace the growth of this idea, as based on actual observa-
tions, we first encounter vague foreshadowings of it in the
seventeenth and the eighteenth centuries. The cells were
seen and sketched by many early observers, but were not
understood.

237

238

BIOLOGY AND ITS MAKERS

As long ago as 1665 Robert Hooke, the great English
microscopist, observed the cellular construction of cork, and
described it as made up of " little boxes or cells distinguished
from one another." He made sketches of the appearance of
this plant tissue; and, inasmuch as the drawings of Hooke
are the earliest ones made of cells, they possess especial in-

FiG. 72. — The Earliest Known Picture of Cells from Hooke 's
Micrographia (1665). From the edition of 1780.

terest and consequently are reproduced here. Fig. 72, taken
from the Micrographia, shows this earliest drawing of Hooke.
He made thin sections with a sharp penknife; "and upon
examination they were found to be all cellular or porous in
the manner of a honeycomb, but not so regular."

We must not completely overlook the fact that Aristotle
(384-322 B.C.) and Galen (130-20C a.d.), those profound
thinkers on anatomical structure, had reached the theoretical
position ''that animals and plants, complex as they may

THE CELL THEORY

239

appear, are yet composed of comparatively few elementary
parts, frequently repeated"; but we are not especially con-
cerned with the remote history of the idea, so much as with
the principal steps in its development after the beginning of
microscopical observations.

Pictures of Cells in the Seventeenth Century. — ^The
sketches illustrating the microscopic observations of Malpighi,

Fig. 73.— Sketch from Malpighi 's Treatise on the Anatomy of
Plants (1670).

Leeuwenhoek, and Grew show so many pictures of the cel-
lular construction of plants that one who views them for the
first time is struck with surprise, and might readily exclaim:
''Here in the seventeenth century we have the foundation of
the cell-theory." But these drawings were merely faithful
representations of the appearance of the fabric of plants;

240 BIOLOGY AND ITS MAKERS

the cells were not thought of as uniform elements of organic
architecture, and no theory resulted. It is true that Malpighi
understood that the cells were separable ''utricles," and that
plant tissue was the result of their union, but this was only
an initial step in the direction of the cell-theory, which, as
we shall see later, was founded on the supposed identity in
development of cells in animals and plants. Fig. 73 show^s
a sketch, made by Malpighi about 1670, illustrating the micro-
scopic structure of a plant. This is similar to the many
drawings of Grew and Leeuwenhoek illustrating the struc-
ture of plant tissues.

Wolff. — Nearly a century after the work of Malpighi, we
find Wolff, in 1759, proposing a theory regarding the organ-
ization of animals and plants based upon observations of
their mode of development. He was one of the most acute
scientific observers of the period, and it is to be noted that his
conclusions regarding structure were all founded upon what he
was able to see; while he gives some theoretical conclusions
of a purely speculative nature, Wolff was careful to keep
these separate from his observations. The purpose of his
investigations was to show that there was no pre-formation
in the embryo; but in getting at the basis of this question, he
worked out the identity of structure of plants and animals
as shown by their development. In his famous publication
on the Theor}^ of Development ( Theoria Generationis) he used
both plants and animals.

Huxley epitomjzes Wolff's views on the development of
elementary parts as follows: ''Every organ, he says, is com-
posed at first of a little mass of clear, viscous, nutritive fluid,
w^hich possesses no organization of any kind, but is at most
composed of globules. In this semifluid mass cavities
(Bldschen, Zellen) are now developed ; these, if they remain
round or polygonal, become the subsequent cells; if they
elongate, the vessels ; and the process is identically the same,

THE CELL THEORY 241

whether it is examined in the vegetating point of a plant, or
in the young budding organs of an animal."

Wolff was contending against the doctrine of pre-forma-
tion in the embryo (see further under the chapter on Embry-
ology), but on account of his acute analysis he should be
regarded, perhaps, as the chief forerunner of the founders of
the cell-theory. He contended for the same method of de-
velopment that was afterward emphasized by Schleiden and
Schwann. Through the opposition of the illustrious physi-
ologist Haller his work remained unappreciated, and was
finally forgotten, until it was revived again in 181 2.

We can not show that Wolff's researches had any direct in-
fluence in leading Schleiden and Schwann to their announce-
ment of the cell-theory. Nevertheless, it stands, intellectually,
in the direct line of development of that idea, while the views
of Haller upon the construction of organized beings are a
side-issue. Haller declared that "the solid parts of animals
and vegetables have this fabric in common, that their ele-
ments are either fibers or unorganized concrete." This
formed the basis of the fiber-theory, which, on account of the
great authority of Haller in physiology, occupied in the
accumulating writings of anatomists a greater place than
the views of Wolff.

Bichat, although he is recognized as the founder of his-
tology, made no original observations on the microscopic units
of the tissues. He described very minutely the membranes
in the bodies of animals, but did not employ the microscope
in his investigations.

Oken. — In the work of the dreamer Oken (i 779-1851),
the great representative of the German school of ''Natur-
philo Sophie,'''' we find, about 1808, a very noteworthy state-
ment to the effect that "animals and plants are throughout
nothing else than manifoldly divided or repeated vesicles, as
I shall prove anatomically at the proper time." This is
16

242 BIOLOGY AND ITS MAKERS

apparently a concise statement of the cell-idea prior to
Schleiden and Schwann; but we know that it was not
founded on observation. Oken, as was his wont, gave rein
to his imagination, and, on his part, the idea was entirely
theoretical, and amounted to nothing more than a lucky guess.

Haller's fiber-theory gave place in the last part of the
eighteenth century to the theory that animals and plants are
composed of globules and formless material, and this globular
theory was in force up to the time of the great generalization
of Schleiden and Schwann. It was well expounded by Milne-
Edwards in 1823, and now we can recognize that at least
some of the globules which he described were the nucleated
cells of later writers.

The Announcement of the Cell-Theory. — ^We are now ap-
proaching the time when the cell-theory was to be launched.
During the first third of the nineteenth century there had ac-
cumulated a great mass of separate observations on the mi-
croscopic structure of both animals and plants. For several
years botanists, in particular, had been observing and writing
about cells, and interest in these structures Vv^as increasing.
*' We must clearly recognize the fact that for some time prior
to 1838 the cell had come to be quite universally recognized
as a constantly recurring element in vegetable and animal
tissues, though little importance was attached to it as an
element of organization, nor had its character been clearly
determined " (Tyson).

Then, in 1838, came the ''master-stroke in generaliza-
tion " due to the combined labors of two friends, Schleiden
and Schwann. But, although these two men are recognized
as co-founders, they do not share honors equally; the work
of Schwann was much more comprehensive, and it was he
who first used the term cell-theory, and entered upon the
theoretical considerations which placed the theory before the
scientific world.

THE CELL THEORY 243

Schleiden was educated as a lawyer, and began the prac-
tice of that profession, but his taste for natural science was
so pronounced that when he was twenty-seven years old
he deserted law, and went back to the university to study
medicine. After graduating in medicine, he devoted himself
mainly to botany. He saw clearly that the greatest thing
needed for the advancement of scientific botany was a study
of plant organization from the standpoint of development.
Accordingly he entered upon this work, and, in 1837, arrived
at a new view regarding the origin of plant cells. It must
be confessed that this new view was founded on erroneous
observations and conclusions, but it was revolutionary, and
ser\'ed to provoke discussion and to awaken observation.
This was a characteristic feature of Schleiden's influence upon
botany. His work acted as a ferment in bringing about new
activity.

The discovery of the nucleus in plant cells by Robert
Brown in 1831 was an important preliminary step to the work
of Schleiden, since the latter seized upon the nucleus as the
starting-point of new cells. He changed the name of the
nucleus to cytoblast, and supposed that the new cell started
as a small clear bubble on one side of the nucleus, and by
continued expansion grew into the cell, the nucleus, or
cytoblast, becoming encased in the cell-wall. All this was
shown by Nageli and other botanists to be wrong; yet, curi-
ously enough, it was through the help of these false observa-
tions that Schwann arrived at his general conclusions.

Schleiden was acquainted with Schwann, and in October,
1838, while the two were dining together, he told Schwann
about his observations and theories. He mentioned in par-
ticular the nucleus and its relationship to the other parts of
the cell. Schwann was immediately struck v/ith the simi-
larity between the observations of Schleiden and certain of his
own upon animal tissues. Together they went to his labo-

244 BIOLOGY AND ITS MAKERS

ratoryand examined the sections of the dorsal cord, the par-
ticular structure upon which Schwann had been working.
Schleiden at once recognized the nuclei in this structure as
being similar to those which he had observed in plants, and
thus aided Schwann to come to the conclusion that the ele-
ments in animal tissues were practically identical with those in
plant tissues.

Schwann. — ^The personalities of the co-founders of the
cell-theory are interesting. Schwann was a man of gentle,
pacific disposition, who avoided all controversies aroused by
his many scientific discoveries. In his portrait (Fig. 74) we see
a man whose striking qualities are good -will and benignity.
His friend Henle gives this description of him : "He was a man
of stature below the medium, with a beardless face, an almost
infantile and always smiling expression, smooth, dark-brown
hair, wearing a fur-trimmed dressing-gown, living in a poorly
lighted room on the second floor of a restaurant which was
not even of the second class. He would pass whole days
there without going out, with a few rare books around him,
and numerous glass vessels, retorts, vials, and tubes, simple
apparatus which he made himself. Or I go in imagina-
tion to the dark and fusty halls of the Anatomical Institute
w^here we used to w^ork till nightfall by the side of our excellent
chief, Johann M tiller. We took our dinner in the evening,
after the English fashion, so that we might enjoy more of the
advantages of daylight."

Schwann drew part of his stimulus from his great master,
Johannes Miiller. He was associated with him as a student,
first in the University of Wiirzburg, where Miiller, with rare
discernment for recognizing genius, selected Schwann for
especial favors and for close personal friendship. The influ-
ence of his long association with Miiller, the greatest of all
trainers of anatomists and physiologists of the nineteenth
century, must have been very uplifting. A few years later,

THE CELL THEORY

245

Schwann found himself at the University of Berlin, where
Miiller had been called, and he became an assistant in the
master's laboratory. There he gained the powerful stimulus
of constant association with a great personality.

Fig. 74. — Theodor Schwann, 1810-1882.

In 1839, just after the publication of his work on the cell-
theory, Schwann was called to a professorship in the Univer-
sity of Louvain, and after remaining there nine years, was
transferred to the University of Liege. He was highly re-

246 BIOLOGY AND ITS MAKERS

spected in the university, and led a useful life, although after
going to Belgium he published only one work — that on the
uses of the bile. He was recognized as an adept experi-

FlG. 75. M. SCHLEIDEN, 1804-1881.

menter and demonstrator, and "clearness, order, and method '*

are designated as the characteristic qualities of his teaching.

His announcement of the cell-theory was his most impor-

THE CELL THEORY 247

tant work. Apart from that his best -known contributions to
science are: experiments upon spontaneous generation, his
discovery of the " sheath of Schwann," in nerve fibers, and
his theory of fermentation as produced by microbes.

Schleiden.— Schleiden (Fig. 75) was quite different in
temperament from Schwann. He did not have the fine self-
control of Schwann, but was quick to take up the gauntlet
and enter upon controversies. In his caustic replies to his
critics, he indulged in sharp personalities, and one is at times
inclined to suspect that his early experience as a lawyer had
something to do with his method of handling opposition.
With all this he had correct ideas of the object of scientific
study and of the methods to be used in its pursuit. He in-
sisted upon observation and experiment, and upon the neces-
sity of studying the development of plants in order to under-
stand their anatomy and physiology. He speaks scornfully
of the botany of mere species-making as follows:

'^ Most people of the world, even the most enlightened, are
still in the habit of regarding the botanist as a dealer in bar-
barous Latin names, as a man who gathers flowers, names
them, dries them, and wraps them in paper, and all of whose
wisdom consists in determining and classifying this hay
which he has collected with such great pains."

Although he insisted on correct micthods, his ardent nature
led him to champion conclusions of his own before they were
thoroughly tested. His great influence in the development
of scientific botany lay in his earnestness, his application of
new methods, and his fearlessness in drawing conclusions,
which, although frequently wrong, formed the starting-point
of new^ researches.

Let us now examine the original publications upon which
the cell-theory was founded.

Schleiden*s Contribution. — Schleiden's paper was par-
ticularly directed to the question. How does the cell originate?

248 BIOLOGY AND ITS MAKERS

and was published in MuUer's ArchiVj in 1838, under the
German title of Ueber Phylogenesis. As stated above, the
cell had been recognized for some years, but the question of
its origin had not been investigated. Schleiden says : '' I may
omit all historical introduction, for, so far as I am acquainted.
no direct observations exist at present upon the development
of the cells of plants."

He then goes on to define his view of the nucleus (cyto-
blast) and of the development of the cell around it, saying:
" As soon as the cytoblasts have attained their full size, a
delicate transparent vesicle arises upon their surface. This
is the young cell." As to the position of the nucleus in the
fully developed cell, he is very explicit: "It is evident," he
says, " from the foregoing that the cytoblast can never lie
free in the interior of the cell, but is always enclosed in the
cell- wall," etc.

Schleiden fastened these errors upon the cell-theory, since
Schwann relied upon his observations. On another point of
prime importance Schleiden was wrong: he regarded all new
cell-formation as the formation of "cells within cells," as dis-
tinguished from cell-division, as we now know it to take place.

Schleiden made no attempt to elaborate his views into a
comprehensive cell-theory, and therefore his connection as
a co-founder of this great generalization is chiefly in paving
the way and giving the suggestion to Schwann, which enabled
the latter to establish the theory. Schleiden's paper occupies
some thirty-two pages, and is illustrated by two plates. He
was thirty-four years old when this paper was published, and
directly afterward was called to the post of adjunct professor
of botany in the University of Jena, a position which with
promotion to the full professorship he occupied for twenty-
three years.

Schwann's Treatise. — In 1838, Schwann also announced
his cell-theory in a concise form in a German scientific period-

THE CELL THEORY 249

ical, and, later, to the Paris Academy of Sciences; but it was
not till 1 839 that the fully illustrated account was published.
This treatise with the cumbersome title, ''Microscopical
Researches into the Accordance in the Structure and Growth
of Animals and Plants" (Mikroscopische Untersuchungenuher
die Uebereinstimmung in der Structur und dem Wachsthum
der Thiere und Pflanzen) takes rank as one of the great classics
in biology. It fills 215 octavo pages, and is illustrated with
four plates.

"The purpose of his researches was to prove the identity
of structure, as shown by their development, between animals
and plants." This is done by direct comparisons of the ele-
mentary parts in the two kingdoms of organic nature.

His writing in the "Microscopical Researches" is clear
and philosophical, and is divided into three sections, in the
first two of which he confines himself strictly to descriptions
of observations, and in the third part of which he enters upon
a philosophical discussion of the significance of the observa-
tions. He comes to the conclusion that "the elementary
parts of all tissues are formed of cells in an analogous, though
very diversified manner, so that it may be asserted that there
is one universal principle of development for the elementary
parts of organisms, however different, and that this principle
is the formation of cells."

It was in this treatise also that he made use of the term
cell-theory, as follows: "The development of the proposition
that there exists one general principle for the formation of all
organic productions, and that this principle is the formation
of cells, as well as the conclusions which may be drawn from
this proposition, may be comprised under the term cell-theory j
using it in its more extended signification, while, in a more
limited . sense, by the theory of cells .we understand whatever
mxay be inferred from this proposition with respect to the
powers from which these phenomena result."

250 BIOLOGY AND ITS MAKERS

One comes from the reading of these two contributions
to science with the feeling that it is really Schwann's cell-
theor)', and that Schleiden helped by lighting the way that
his fellow- worker so successfully trod.

Modification of the Cell-Theory. — ^The form in which the
cell- theory was given to the world by Schleiden and Schwann
was very imperfect, and, as already pointed out, it contained
fundamental errors. The founders of the theory attached
too much importance to the cell -wall, and they described the
cell as a hollow cavity bounded by walls that were formed
around a nucleus. They were wrong as to the mode of the
development of the cell, and as to its nature. Nevertheless,
the great truth that all parts of animals and plants are built
of similar units or structures was well substantiated. This
remained a permanent part of the theory, but all ideas re-
garding the nature of the units were profoundly altered.

In order to perceive the line along which the chief modifi-
cations were made we must take account of another scientific
advance of about the same period. This was the discovery
of protoplasm, an achievement which takes rank with the
advances of greatest importance in biology, and has proved
to be one of the great events of the nineteenth century.

The Discovery of Protoplasm and its Effect on the Cell-
Theory. — In 1835, before the announcement of the cell-
theory, living matter had been observed by Dujardin. In
lower animal forms he noticed a semifluid, jelly-like sub-
stance, which he designated sarcode, and which he described
as being endowed with all the qualities of life. The same
semifluid substance had previously caught the attention of
some observ^ers, but no one had as yet announced it as the
actual living part of organisms. Schleiden had seen it and
called it gum. Dujardin was far from appreciating the full
importance of his discover}-, and for a long time his descrip-
tion of sarcode remained separate; but in 1846 Hugo von

THE CELL THEORY 251

Mohl, a botanist, observed a similar jelly-like substance in
plants, which he called plant schleim, and to which he attached
the name protoplasma.

The scientific world was now in the position of recogniz-
ing living substance, which had been announced as sarcode
in lower animals, and as protoplasm in plants; but there
was as yet no clear indication that these two substances
were practically identical. Gradually there came stealing
into the minds of observers the suspicion that the sarcode of
the zoologists and the protoplasm of the botanists were one
and the same thing. This proposition was definitely main-
tained by Cohn in 1850, though with him it was mainly
theoretical, since his observations were not sufficiently ex-
tensive and accurate to support such a conclusion.

Eleven years later, however, as the result of extended
researches, Max Schultze promulgated, in 1861, the proto-
plasm doctrine, to the effect that the units of organization
consist of little masses of protoplasm surrounding a nucleus,
and that this protoplasm, or living substance, is practically
identical in both plants and animals.

The effect of this conclusion upon the cell-theory was
revolutionary. During the time protoplasm was being ob-
served the cell had likewise come under close scrutiny, and
naturalists had now an extensive collection of facts upon
which to found a theory. It has been shown that many
animal cells have no cell-wall, and the final conclusion was
inevitable that the essential part of a cell is the semifluid
living substance that resides within the cavity when a cell-
wall is present. Moreover, when the cell-wall is absent, the
protoplasm is the "cell." The position of the nucleus was
also determined to be within the living substance, and not,
as Schleiden had maintained, within the cell-wall. The
definition of Max Schultze, that a cell is a globule of proto-
plasm surrounding a nucleus, marks a new era in the cell-

252 BIOLOGY x\ND ITS MAKERS

theory, in which the original generalization became consoli-
dated with the protoplasm doctrine.

Further Modifications of the Cell-Theory. — ^The reformed
cell-theory was, however, destined to undergo further modifi-
cation, and to become greatly extended in its application.
At first the cell was regarded merely as an element of struc-
ture; then, as a supplement to this restricted view, came the
recognition that it is also a unit of physiology, viz., that all
physiological activities take place within the cell. Matters
did not come to a rest, however, with the recognition of these
two fundamental aspects of the cell. The importance of the
cell in development also took firmer hold upon the minds of
anatomists after it was made clear that both the egg and its
fertilizing agents are modified cells of the parent's body. It
was necessary to comprehend this fact in order to get a clear
idea of the origin of cells within the body of a multicellular
organism, and of the relation between the primordial element
and the fully developed tissues. Finally, when observ^ers
found within the nucleus the bearers of hereditary qualities,
they began to realize that a careful study of the behavior of
the cell elements during development is necessar}^ for the
investigation of hereditary transmissions.

A statement of the cell-theory at the present time, then,
must include these four conceptions: the cell as a unit of
structure, the cell as a unit of physiological activity, the cell
as embracing all hereditary qualities within its substance,
and the cell in the historical development of the organism.

Some of these relations may now be more fully illustrated.

Origin of Tissues. — ^The egg in which all organisms above
the very lowest begin, is a single cell having, under the micro-
scope, the appearance shown in Fig. 76. After fertilization,
this divides repeatedly, and many cohering cells result. The
cells are at first similar, but as they increase in number, and
as development proceeds, they grow different, and certain

THE CELL THEORY

253

groups are set apart to perform particular duties. The divi-
sion of physiological labor which arises at this time m.arks
the beginning of separate tissues. It has been demonstrated
over and over that all tissues are composed of cells and cell-
products, though in some instances they are much modified.
The living cells can be seen even in bone and cartilage, in

Fig. 76. — ^The Egg and Early Stages in its Development.
(After Gegenbaur.)

which they are separated by a lifeless matrix, the latter being
the product of cellular activity.

Fig. 77 shows a stage in the development of one of the
mollusks just as the differentiation of cells has commenced.

The Nucleus. — ^To the earlier observers the protoplasm
appeared to be a structureless, jelly-like mass containing
granules and vacuoles; but closer acquaintance with it has
shown that it is in reality very complex in structure as well
as in chemical composition. It is by no means homogeneous;
adjacent parts are different in properties and aptitudes. The
nucleus, which is more readily seen than other cell elements,

254 BIOLOGY AND ITS MAKERS

was shown to be of great importance in cell-life — to be a
structure which takes the lead in cell division, and in general
dominates the rest of the protoplasm.

Chromosomes. — After dyes came into use for staining the
protoplasm (1868), it became evident that certain parts of it
stain deeply, while other parts stain faintly or not at all. This
led to the recognition of protoplasm as made up of a densely
staining portion called chromatin, and a faintly staining por-

FiG. 77. — An Early Stage in the Development of the Egg of a Rock-
Limpet. (After Conklin.)

tion designated achromatin. This means of making different
parts of protoplasm visible under the microscope led to im-
portant results, as when, in 1883, it was discovered that the
nucleus contains a definite number of small (usually rod-
shaped) bodies, which become evident during nuclear divi-
sion, and play a wonderful part in that process. These bodies
take the stain more deeply than other components of the
nucleus, and are designated chromosomes.

Attention having been directed to these little bodies,
continued observations showed that, although they vary in

THE CELL THEORY

255

number — commonly from two to twenty -four — in different
parts of animals and plants, they are, nevertheless, of the
same number in all the cells of any particular plant or ani-

Fig. 78. — Highly Magnified Tissue Cells from the Skin of a
Salamander in an Active State of Growth. Dividing cells with
chromosomes are shown at a, b, and c,. (After Wilson.)

mal. As a conclusion to this kind of observation, it needs
to be said that the chromosomes are regarded as the actual
bearers of hereditary cjualities. The chromosomes do not

256

BIOLOGY AND ITS MAKERS

show in resting-stages of the nucleus; their substance is
present, but is not aggregated into the form of chromosomes.
Fig. 78 shows tissue cells, some of which are in the divid-
ing and others in the resting-stage. The nuclei in process of

C

\r

is \

cM

^^\li/ ,

SHKIi

r^A

Fig. 79. — Diagram of the Chief Steps in Cell-division.
(After Parker as altered from Flemming.)

division exhibit the rod-like chromosomes, as shown at a,
J, and c.

Centrosome. — ^The discovery (1876) of a minute spot of
deeply staining protoplasm, usually just outside the nuclear

THE CELL THEORY

257

membrane, is another illustration of the complex structure
of the cell. Although the ccntrosome, as this spot is called,
has been heralded as a dynamic agent, there is not complete
agreement as to its purpose, but its presence makes it necess-
sary to include it in the definition of a cell.

The Cell in Heredity. — The problems of inheritance, in
so far as they can be elucidated by structural studies, have
come to be recognized as problems of cellular life. But we
cannot understand what is implied by this conclusion without
referring to the behavior of the chromosomes during cell-
division. This is a very complex process, and varies som.e-
what in different tissues. We can,
however, with the help of Fig. 79,
describe what takes place in a typical
case. The nucleus does not divide
directly, but the chromosomes congre-
gate around the equator of a spindle
(D) formed from the achromatin; they
then undergo division lengthwise, and
migrate to the poles (E, F, G), after
which a partition w^all is formed divid-
ing the cell. This manner of division
of the chromosomes secures an equable
partition of the protoplasm. In the
case of fertilized eggs, one-half of the
chromosomes are derived from the
sperm and one-half from the egg.
Each cell thus contains hereditary
substance derived from both mater-
nal and paternal nuclei. This is briefly the basis for re-
garding inheritance as a phenomenon of cell-life.

A diagram of the cell as now understood (Pig. 80) will
be helpful in showing how much the conception of the cell
has changed since the time of Schleiden and Schwann.
17

Fig. 80. — Diagram
of a Cell. (Modified
after Wilson.)

258 BIOLOGY AND ITS MAKERS

Definition. — The definition of Verworn, made in 1895,
may be combined with this diagram: A cell is ''a body con-
sisting essentially of protoplabm in its general form, including
the unmodified cytoplasm, and the specialized nucleus and
centrosome; while as unessential accompaniments may be
enumerated: (i) the cell membrane, (2) starch grains, (3)
pigment granules, (4) oil globules, and (5) chlorophyll gran-
ules." No definition can include all variations, but the one
quoted is excellent in directing attention to the essentials — •
to protoplasm in its general form, and the modified proto-
plasmic parts as distinguished from the unessential accom-
paniments, as cell membrane and cell contents.

The definition of Verworn was reached by a scries of
steps representing the historical advance of knowledge regard-
ing the cell. Schleiden and Schwann looked upon the cell
as a hollow chamber having a cell-wall which had been
formed around the nucleus; it was a great step when
Schultze defined the cell in terms of living substance as "a
globule of protoplasm surrounding a nucleus," and it is a
still deeper level of analysis which gives us a discriminating
definition like that of Verworn.

When we are brought to realize that, in large part, the
questions that engage the mind of the biologist have their
basis in the study of cells, we are ready to appreciate the force
of the statement that the establishment of the cell-theory
was one of the great events of the nineteenth century, and,
further, that it stands second to no theory, with the single
exception of that of organic evolution, in advancing bio-
logical science.

CHAPTER Xll

PROTOPLASM, THE PHYSICAL BASIS OF LIFE

The recognition of the role that protoplasm plays in the
living world was so far-reaching in its results that we take
up for separate consideration the history of its discovery. Al-
though it is not yet fifty years since Max Schultze established
the protoplasm doctrine, it has already had the greatest
influence upon the progress of biology. To the consideration
of protoplasm in the previous chapter should be added an
account of the conditions of its discovery, and of the person-
ality and views of the men whose privilege it was to bring
the protoplasm idea to its logical conclusion. Before doing
so, however, we shall look at the nature of protoplasm
itself.

Protoplasm. — ^This substance, which is the seat of all
vital activity, was designated by Huxley " the physical basis
of life," a graphic expression which brings before the mind the
central fact that life is manifested in a material substratum
by which it is conditioned. All that biologists have been able
to discover regarding life has been derived from the observa-
tion of that material substratum. It is not difficult, with the
help of a microscope, to get a view of protoplasmic activity,
and that which was so laboriously made known about i860
is now shown annually to students beginning biology.

Inasmuch as all living organisms contain protoplasm,
one has a wide range of choice in selecting the plant or the
animal upon which to make observations.

We may, for illustration, take one of the simplest of animal
organisms, the amoeba, and place it under the high powers

259

20O BIOLOGY AND ITS MAKERS

of the microscope. This little animal consists almost entirely
of a lump of living jelly. Within the living substance of
which its body is composed all the vital activities character-
istic of higher animals are going on, but they are manifested
in simpler form. These manifestations differ only in degree
of development, not in kind, from those we see in bodies of
higher organisms.

We can watch the movements in this amoeba, deter-
mine at first hand its inherent qualities, and then draw up
a sort of catalogue of its vital properties. We notice an
almost continual flux of the viscid substance, by means of
which it is able to alter its form and to change its position.
This quality is called that of contractility. In its essential
nature it is like the protoplasmic movement that takes place
in a contracting muscle. We find also that the substance
of the amoeba responds to stimulations — such as touching
it with a bristle, or heating it, or sending through it a light
electric shock. This response is quite independent of the
contractility, and by physiologists is designated the property
of being irritable.

By further observations one may determine that the sub-
stance of the amoeba is receptive and assimilative, that it is
respiratory, taking in oxygen and giving off carbonic dioxide,
and that it is also secretor}-. If the amoeba be watched
long enough, it may be seen to undergo division, thus produc-
ing another individual of its kind. We say, therefore, that it
exhibits the power of reproduction. All these properties
manifested in close association in the am.oeba are exhibited
in the bodies of higher organisms in a greater degree of
perfection, and also in separation, particular organs often
being set apart for the performance of one of these par-
ticular functions. We should, however, bear in mind that
in the simple protoplasm of the amoeba is found the germ of
all the activities of the higher animals.

THE PHYSICAL BASIS OF LIFE

261

It will be convenient now to turn our attention to the
microscopic examination of a plant that is sufficiently trans-
parent to enable us to look within its living parts and observe
the behavior of protoplasm. The first thing that strikes one
is the continual activity of the living substance within the
boundaries of a particular cell. This movement sometimes

tear's ;;?|-| I •'V;V;v

Fig. 81, — (A) Rotation of Protoplasm in the Cells of Nitella.
(B) Highly Magnified Cell of a Tradescantia Plant, Showing
Circulation of Protoplasm. (After Sedgwick and Wilson.)

takes the form of rotation around the walls of the cell (Fig.
81 A). In other instances the protoplasm marks out for itself
new paths, giving a more complicated motion, called circula-
tion (Fig. 81 5). These movements are the result of chemi-
cal changes taking place within the protoplasm, and they are
usually to be observed in any plant or animal organism.

Under the most favorable conditions these movements, as
seen under the microscope, make a perfect torrent of un-
ceasing activity, and introduce us to one of the wonderful
sights of which students of biology have so many. Huxley

262 BIOLOGY AND ITS MAKERS

(with slight verbal alterations) says : "The spectacle afforded
by the wonderful energies imprisoned within the compass of
the microscopic cell of a plant, which we commonly regard
as a merely passive organism, is not easily forgotten by one
who has watched its movement hour by hour without pause
or sign of weakening. The possible complexity of many
other organisms seemingly as simple as the protoplasm of
the plant just mentioned dawns upon one, and the compari-
son of such activity to that of higher animals loses much
of its startling character. Currents similar to these have
been observed in a great multitude of very different plants,
and it is quite uniformly believed that they occur in more
or less perfection in all young vegetable cells. If such be
the case, the wonderful noonday silence of a tropical forest
is due, after all, only to the dullness of our hearing, and could
our ears catch the nmrmur of these tiny maelstroms as they
whirl in the innumerable myriads of living cells that con-
stitute each tree, we should be stunned as with the roar of a
great city."

The Essential Steps in Recognizing the Likeness of
Protoplasm in Plants and Animals

Dujardin. — This substance, of so much interest and im-
portance to biologists, was first clearly described and dis-
tinguished from other viscid substance, as albumen, by Felix
Dujardin in 1835. ^^^th the substance and the movements
therein had been seen and recorded by others: by Rosel
von Rosenhof in 1755 in the proteus animalcule; again in
1772 by Corti in chara; by Mayen in 1827 in Vallisnieria;
and in 1831 by Robert Brown in Tradescantia. One of these
records was for the animal kingdom, and three were for
plants. The observations of Dujardin, however, were on a
different plane from those of the earlier naturalists, and he

THE PHYSICAL BASIS OF LIFE 263

is usually credited with being the discoverer of protoplasm.
His researches, moreover, were closely connected with the
development of the ideas regarding the role played in nature
by this living substance.

Dujardin was a quiet modest man, whose attainments and
service to the progress of biology have usually been under-
rated. He was born in 1801 at Tours, and died in i860 at
Rennes. Being descended from a race of watchmakers, he
received in his youth a training in that craft which cultivated
his natural manual dexterity, and, later, this assisted him in
his manipulations of the microscope. He had a fondness for
sketching, and produced some miniatures and other works
of art that showed great merit. His use of colors was very
effective, and in 181 8 he went to Paris for the purpose of
perfecting himself in painting, and with the intention of
becoming an artist. The small financial returns, however,
^'led him to accept work as an engineer directing the con-
struction of hydraulic work in Sedan." He had already
shown a love for natural science, and this led him from engin-
eering into work as a librarian and then as a teacher. He
made field observations in geolog}' and botany, and com-
menced publication in those departments of science.

About 1834 he began to devote his chief efforts to
microscopic work, toward which he had a strong inclination,
and from that time on he became a zoologist, with a steadily
growing recognition for high-class observation. Besides his
technical scientific papers, he wrote in a popular vein to
increase his income. Among his writings of this type may be
mentioned as occupying high rank his charmingly written
^'Rambles of a Naturalist" {Promenades d'un Naturaliste,
1838).

By 1840 he had established such a good record as a sci-
■entific investigator that he was called to the newly founded
University of Rennes as dean of the faculty. He found him-

264 BIOLOGY AND ITS MAKERS

self in an atmosphere of jealous criticism, largely on account
of his being elevated to the station of dean, and after two
years of discomfort he resigned the deanship, but retained
his position as a professor in the university. He secured a
residence in a retired spot near a church, and lived there
simply. In his leisure moments he talked frequently with
the priests, and became a devout Catholic.

His contributions to science cover a wide range of subjects.
In his microscopic work he discovered the rhizopods in 1834,
and the study of their structure gave him the key to that of
the other protozoa. In 1835 he visited the Mediterranean,
where he studied the oceanic foraminifera, and demonstrated
that they should be grouped with the protozoa, and not, as
had been maintained up to that time, with the mollusca.
It was during the prosecution of these researches that he
made the observations upon sarcode that are of particular
interest to us.

His natural history of the infusoria (1841) makes a vol-
ume of 700 pages, full of original observations and sketches.
He also invented a means of illumination for the microscope,
and wrote a manual of microscopic observation. Among the
ninety-six publications of Dujardin listed by Professor Joubin
there are seven general works, twenty relating to the protozoa,
twenty-four to geology, three to botany, four to physics,
twenty-five to arthropods, eight to worms, etc., etc. But as
Joubin says: "The great modesty of Dujardin allowed him
to see published by others, without credit to himself, numer-
ous facts and observations which he had established." This
failure to assert his claims accounts in part for the inadequate
recognition that his work has received.

No portrait of Dujardin was obtainable prior to 1898.
Somewhat earlier Professor Joubin, who succeeded other
occupants of the chair which Dujardin held in the University
of Rennes, found in the possession of his descendants a

THE PHYSICAL BASIS OF LIFE 265

portrait, which he was permitted to copy. The earliest re-
production of this picture to reach this country came to the

Fig. 82. — Felix Dujardin, 1801-1860.

writer through the courtesy of Professor Joubin, and a copy
of it is represented in Fig. 82. His picture bespeaks his per-
sonaHty. The quiet refinement and sincerity of his face are

266 BIOLOGY AND ITS MAKERS

evident. Professor Joubin published, in 1901 (Archives de
Parasitologie), a biographical sketch of Dujardin, with sev-
eral illustrations, including this portrait and another one
which is very interesting, showing him in academic costume.
Thanks to the spread of information of the kind contained
in that article, Dujardin is coming into wider recognition,
and will occupy the historical position to which his researches
entitle him.

It was while studying the protozoa that he began to take
particular notice of the substance of which their bodies are
composed; and in 1835 he described it as a living jelly
endowed with all the qualities of life. He had seen the same
jelly-like substance exuding from the injured parts of worms,
and recognized it as the same material that makes the body
of protozoa. He observed it very carefully in the ciliated
infusoria — in Paramoecium, in Vorticella, and other forms,
but he was not satisfied with mere microscopic observation
of its structure. He tested its solubility, he subjected it to
the action of alcohol, nitric acid, potash, and other chemical
substances, and thereby distinguished it from albumen,
mucus, gelatin, etc.

Inasmuch as this substance manifestly was soft, Dujardin
proposed for it the name of sarcode, from the Greek, meaning
sojt. Thus we see that the substance protoplasm was for
the first time brought very definitely to the attention of nat-
uralists through the study of animal forms. For some time it
occupied a position of isolation, but ultimately became recog-
nized as being identical with a similar substance that occurs
in plants. At the time of Dujardin's discover}^, sarcode was
supposed to be peculiar to lower animals ; it was not known
that the same substance made the living part of all animals,
and it was owing mainly to this circumstance that the full
recognition of its importance in nature was delayed.

The fact remains that the first careful studies upon sarcode

THE PHYSICAL BASIS OF LIFE

267

were due to Dujardin, and, therefore, we must include him
among the founders of modem biology.

Purkinje. — The observations of the Bohemian investi-
gator Purkinje (1787-1869) form a link in the chain of events
leading up to the recognition of protoplasm. Athough
Purkinje is especially remembered for other scientific contri-

FiG. 83. — Purkinje, 1787-1869.

butions, he was the first to make use of the name protoplasm
for living matter, by applying it to the formative substance
within the eggs of animals and within the cells of the embryo.
His portrait is not frequently seen, and, therefore, is included
here (Fig. 83), to give a more complete series of pictures of
the men who were directly connected with the development
of the protoplasm idea. Purkinje was successively a pro-

268

BIOLOGY AND ITS MAKERS

fessor in the universities of Breslau and Prague. His ana-
tomical laboratory at Breslau is notable as being one of the
earliest (1825) open to students. He went to Prague in
1850 as professor of physiology.

Von Mohl. — In 1846, eleven years after the discovery of
Dujardin, the eminent botanist Hugo von Mohl (1805-1872)
designated a particular part of the living contents of the vege-
table cell by the term protoplasma. The viscid, jelly-like

Fig. 84. — Carl Nageli, 181 7-1 891.

substance in plants had in the mean time come to be known
under the expressive term of plant ''schleim." He distin-
guished the firmer mucilaginous and granular constituent,
found just under the cell membrane, from the watery cell-sap
that occupies the interior of the cell. It was to the former
part that he gave the name protoplasma. Previous to this,

THE PHYSICAL BASIS OF LIFE 269

the botanist Nageli had studied this living substance, and
perceived that it was nitrogenous matter. This was a dis-
tinct step in advance of the vague and indefinite idea of
Schleiden, who had in reality noticed protoplasm in 1838,
but thought of it merely as gum. The highly accom])lished
investigator N ageli (Fig. 84) made a great place for himself

Fig. 85. — Hugo von Mohl, 1805-1872.

in botanical investigation, and his name is connected with
several fundamental ideas of biology. To Von Mohl, how-
ever, belongs the credit of having brought the word proto-
plasm into general use. He stands in ,the direct line of
development, while Purkinje, who first employed the word

27© BIOLOGY AND ITS MAKERS

protoplasm, stands somewhat aside, but his name, neverthe-
less, should be connected with the establishment of the
protoplasm doctrine.

Von Mohl (Fig. 85) was an important man in botany.
Early in life he showed a great love for natural science, and
as in his day medical instruction afforded the best oppor-
tunities for a man with scientific tastes, he entered upon that
course of study in Tubingen at the age of eighteen. He took
his degree of doctor of medicine in 1823, and spent several
years in Munich. He became professor of physiology in
Bern in 1832, and three years later was transferred to
Tubingen as professor of botany. Here he remained to the
end of his life, refusing invitations to institutions elsewhere.
He never married, and, without the cares and joys of a
family, led a solitary and uneventful life, devoted to botan-
ical investigation.

Cohn. — ^After Von Mohl's studies on "plant schleim'^
there was a general movement toward the conclusion that
the sarcode of the zoologists and the protoplasm of the bot-
anists were one and the same substance. This notion was in
the minds of more than one worker, but it is perhaps to Fer-
dinand Cohn (i 828-1 898) that the credit should be given
for bringing the question to a head. After a study of the
remarkable movements of the active spores of one of the
simplest plants (protococcus), he said that vegetable proto-
plasm and animal sarcode, "if not identical, must be, at
any rate, in the highest degree analogous substances "
(Geddes). •

Cohn (Fig. 86) was for nearly forty years professor of
botany in the University of Breslau, and during his long life
as an investigator greatly advanced the knowledge of bac-
teria. His statement referred to above was made when he
was twenty-two years of age, and ran too far ahead of the
evidence then accumulated; it merely anticipated the com-

THE PHYSICAL BASIS OF LIFE

271

ing period of the acceptance of the conclusion in its full
significance.

De Bary. — We find, then, in the middle years of the
nineteenth century the idea launched that sarcode and pro-
toplasm are identical, but it was not yet definitely established

Fig. 86. — Ferdinand Cohn, 1828-1898.

that the sarcode of lower animals is the same as the living
substance of the higher ones, and there was, therefore, lacking
an essential factor to the conclusion that there is only one
general form of living matter in all organisms. It took
another ten years of investigation to reach this end.

The most important contributions from the botanical side
during this period were the splendid researches of De Bar}^
(Fig. 87) on the myxomycetes, published in 1859. Here the
resemblance between sarcode and protoplasm was brought out

272

BIOLOGY AND ITS MAKERS

with great clearness. The myxomycetes are, in one condition,
masses of vegetable protoplasm, the movements and other
characieristics of which were shown to resemble strongly
those of the protozoa. DeBary's great fame as a botanist
has made his name widely known.

In 1858 Virchow also, by his extensive studies in the
pathology of living cells, added one more link to the chain

Fig. 87. — Heinrich A. de Bary, 1831-1888.

that was soon to be recognized as encircling the new domain
of modern biology.

Schultze. — ^As the culmination of a long period of work,
Max Schultze, in t86t. placed the conception of the identity

THE PHYSICAL BASIS OF LIFE

273

between animal sarcode and vegetable protoplasm upon an
unassailable basis, and therefore he has received the title of

Fig. 88. — Max Schultze, 1825-1874.

"the father of modern biology." He showed that sarcode,
which was supposed to be confined to the lower invertebrates,
is also present in the tissues of higher animals, and there ex-

iS

274 BIOLOGY AND ITS MAKERS

hibits the same properties. The quahties of contractility and
irritability were especially indicated. It was on physiological
likeness, rather than on structural grounds, that he formed
his sweeping conclusions. He showed also that sarcode
agreed in physiological properties with protoplasm in plants,
and that the two living substances were practically identical.
His paper of 1861 considers the living substance in muscles
(Ueber Muskelkorperchen und das was man eine Zelle zu
nennen habe), but in this he had been partly anticipated by
Ecker who, in 1849, compared the ''formed contractile sub-
stance" of muscles with the " unformed contractile substance'*
of the lower types of animal life (Geddes).

The clear-cut, intellectual face of Schultze (Fig. 88) is
that of an admirable man with a combination of the artistic
and the scientific temperaments. He was greatly interested
in music from his youth up, and by the side of his microscope
was his well-beloved violin. He was some time professor in
the University of Halle, and in 1859 went to Bonn as pro-
fessor of anatomy and director of the Anatomical Institute.
His service to histology has already been spoken of (Chapter
VIII).

This astute observer will have an enduring fame in
biological science, not only for the part he played in the
development of the protoplasm idea, but also on account of
other extensive labors. In 1866 he founded the leading
periodical in microscopic anatomy, the Archiv jiir Mikro-
scopische Anatomie. This periodical was continued after
the untimely death of Schultze in 1874, and to-day is one of
the leading biological periodicals.

It is easy, looking backward, to observe that the period
between 1840 and i860 was a very important one for modem
biology. Many new ideas were coming into existence, but
through this period we can trace distinctly, step by step, the
gradual approach to the idea that protoplasm, the living

THE PHYSICAL BASIS OF LIFE 275

substance of organism, is practically the same in plants and
in animals. Let us picture to ourselves the consequences of
the acceptance of this idea. Now for the first time physiol-
ogists began to have their attention directed to the actually
living substance; now for the first time they saw clearly
that all future progress was to be made by studying this living
substance — the seat of vital activity. This was the beginning
of modern biology.

Protoplasm is the particular object of study for the biol-
ogist. To observe its properties, to determine how it be-
haves under different conditions, how it responds to stimuli
and natural agencies, to discover the relation of the internal
changes to the outside agencies : these, which constitute the
fundamental ideas of biology, were for the first time brought
directly to the attention of the naturalist, about the year
i860 — that epoch-making time when appeared Darwin's
Origin oj Species and Spencer's First Principles,

CHAPTER XIII

THE WORK OF PASTEUR, KOCH, AND OTHERS

The knowledge of bacteria, those minutest forms of life,
has exerted a profound influence upon the development of
general biology. There are many questions relating to bac-
teria that are strictly medical, but other phases of their life
and activities are broadly biological, and some of those
broader aspects will next be brought under consideration.

The bacteria were first described by I^eeuwenhoek in
1687, twelve years after his discovery of the microscopic
animalcula now called protozoa. They are so infinitesimal
in size that under his microscope they appeared as mere
specks, and, naturally, observation of these minute organ-
isms was suspended until nearly the middle of the nineteenth
century, after the improvement of microscope lenses. It is
characteristic of the little knowledge of bacteria in Linnaeus's
period that he grouped them into an order, with other micro-
scopic forms, under the name chaos.

At first sight, the bacteria appear too minute to figure
largely in human affairs, but a great department of natural
science — bacteriology— has been opened by the study of their
activities, and it must be admitted that the development of
the science of bacteriology has been of great practical im-
portance. The knowledge derived from experimental studies
of the bacteria has been the chief source of light in an obscure
domain which profoundly affects the well-being of mankind.
To the advance of such knowledge we owe the germ-theory
of disease and the ability of medical men to cope with con-

276

PASTEUR, KOCH, AND OTHERS 277

tagious diseases. The three greatest names connected with
the rise of bacteriology are those of Pasteur, Koch, and Lister,
the resuks of whose labors will be considered later.

Among the general topics which have been clustered
around the study of bacteria we take up, first, the question
of the spontaneous origin of life.

The Spontaneous Origin of Life

It will be readily understood that the question of the spon-
taneous generation of life is a fundamental one for the biol-
ogist. Does life always arise from previously existing life,
or under certain conditions is it developed spontaneously?
Is there, in the inorganic world, a happy concourse of atoms
that beconie chained together through the action of the sun's
rays and other natural forces, so that a molecule of living
matter is constructed in nature's laboratory without contact
or close association with living substance? This is a ques-
tion of biogenesis — life from previous life — or of abiogenesis
— life without preexisting life or from inorganic matter alone.

It is a question with a long histor}^ Its earliest phases do
not involve any consideration of microscopic forms, since they
were unknown, but its middle and its modern aspect are con-
cerned especially with bacteria and other microscopic organ-
isms. The historical development of the problem may be
conveniently considered under three divisions : I. The period
from Aristotle, 325 B.C., to the experiments of Redi, in 1668;
II. From the experiments of Redi to those of Schulze and
Schwann in 1836 and 1837; III. The modern phase, ex-
tending from Pouch et's observations in 1859 to the present.

I. From Aristotle to Redi. — During the first period, the
notion of spontaneous generation was universally accepted,
and the whole question of spontaneous origin of life was in
a crude and grotesque condition. It was thought that frogs

278 BIOLOGY AND ITS MAKERS

and toads and other animals arose from the mud of ponds
and streams through the vivifying action of the sun's rays.
Rats were supposed to come from the river Nile, the dew was
supposed to give origin to insects, etc.

The scientific writers of this period had little openness of
mind, and they indulged in scornful and sarcastic comments
at the expense of those who doubted the occurrence of
spontaneous generation. In the seventeenth century Alex-
ander Ross, commenting on Sir Thomas Brown's doubt as
to whether mice may be bred by putrefaction, flays his an-
tagonist in the following words: "So may we doubt whether
in cheese and timber worms are generated, or if beetles and
wasps in cow-dung, or if butterflies, locusts, shell-fish, snails,
eels, and such life be procreated of putrefied matter, which
is to receive the form of that creature to which it is by
formative power disposed. To question this is to question
reason, sense, and experience. If he doubts this, let him go
to Egypt, and there he will find the fields swarming with
mice begot of the mud of Nylus, to the great calamity of
the inhabitants."

II. From Redi to Schwann. — ^The second period em-
braces the experimental tests of Redi (1668), Spallanzani
(1775), and Schwann (1837) — ^notable achievements that
resulted in a verdict for the adherents to the doctrine of
biogenesis. Here the question might have rested had it
not been opened upon theoretical ground by Pouchet in
1859.

The First Experiments. — The belief in spontaneous gen-
eration, which was so firmly implanted in the minds of natu-
ralists, was subjected to an experimental test in 1668 by the
Italian Redi. It is a curious circumstance, but one that
throws great light upon the condition of intellectual develop-
ment of the period, that no one previous to Redi had at-
tempted to test the truth or falsity of the theory of spon-

PASTEUR, KOCH, AND OTHERS 279

taneous generation. To approach this question from the
experimental side was to do a great service to science.

The experiments of Redi were simple and homely. He
exposed meat in wide-mouthed flasks, some of which were left
uncovered, some covered with paper, and others with a fine
Neapolitan veil. The meat in all these vessels became
spoiled, and flies, being attracted by the smell of decaying
mieat, laid eggs in that which was exposed, and there came
from it a large crop of maggots. The meat in the covered
ilasks also decayed in a similar manner, without the appear-
ance of maggots within it; and in those vessels covered by
veiling the flies laid their eggs upon the netting. There they
hatched, and the maggots, instead of appearing in the meat,
appeared on the surface of the covering. From this Redi con-
cluded that maggots arise in decaying meat from the hatching
of the eggs of insects, but inasmuch as these animals had been
supposed to arise spontaneously within the decaying meat, the
experiment took the ground from under that hypothesis.

He made other observations on the generation of insects,
but with acute scientific analysis never allowed his conclusions
to run ahead of his observations. He suggested, however,
the probability that all cases of the supposed production of life
from dead matter were due to the introduction of living germs
from without. The good work begun by Redi was confirmed
and extended by Swammerdam (1637-1681) and Vallisnieri
(1661-1730), until the notion of the spontaneous origin of any
forms of life visible to the unaided eye was banished from
the minds of scientific men.

Redi (Fig. 89) was an Italian physician living in Arentino,
distinguished alike for his attainments in literature and for
his achievements in natural science. He was medical adviser
to two of the grand dukes of Tuscany, and a member of the
Academy of Crusca. Poetry as well as other literary com-
positions shared his time with scientific occupations. His

28o

BIOLOGY AND ITS MAKERS

collected works, literary, scientific, and medical, were pub-
lished in nine octavo volumes in Milan, 1809-1811. This
collection includes his life and letters, and embraces one

Fig. 89. — Francesco Redi, 1626-1697.

volume of sonnets. The book that has been referred to as
containing his experiments was entitled Esperienze Intorno
Alia Generazione DegPInsetti, and first saw the light in
quarto form in Florence in 1668. It went through five
editions in twenty years. Some of the volumes were trans-

PASTEUR, KOCH, AND OTHERS 281

lated into Latin, and were published in miniature, making
books not more than four inches high. Huxley says: "The
extreme simplicity of his experiments, and the clearness of
his arguments, gained for his views and for their conse-
quences almost universal acceptance."

New Form of the Question.— The question of the spon-
taneous generation of life was soon to take on a new aspect.
Seven years after the experiments of Redi, Leeuwenhoek
made known a new world of microscopic organisms — the
infusoria — and, as we have seen, he discovered, in 1687, those
still minuter forms, the bacteria. Strictly speaking, the
bacteria, on account of their extreme minuteness, were lost
sight of, but spontaneous generation was evoked to account
for the birth of all microscopic organisms, and the question
circled mainly around the infusorial animalcula. While the
belief in the spontaneous generation of life among forms
visible to the unaided eye had been surrendered, nevertheless
doubts were entertained as to the origin of microscopic organ-
isms, and it was now asserted that here were found the be-
ginnings of life — the place where inorganic material was
changed through natural agencies into organized beings
microscopic in size.

More than seventy years elapsed before the matter was
again subjected to experimental tests. Then Needham,
using the method of Redi, began to experiment on the pro-
duction of microscopic animalcula. In many of his experi-
ments he was associated with Buffon, the great French nat-
uralist, who had a theory of organic molecules that he wished
to sustain. Needham (1713-1784), a priest of the Catholic
faith, was an Englishman living on the Continent ; he was
for many years director of the Academy of Maria Theresa at
Brussels. He engaged in scientific investigations in connec-
tion with his work of teaching. The results of Needham's
first experiments were published in 1 748. These experiments

282 BIOLOGY AND ITS MAKERS

were conducted by extracting the juices of meat by boiling;
by then enclosing the juices in vials, the latter being carefully
corked and sealed with mastic; by subjecting the sealed
bottles, finally, to heat, and setting them away to cool. In
due course of time, the fluids thus treated became infected
with microscopic life, and, inasmuch as Ncedham believed
that he had killed all living germis by repeated heating, he
concluded that the living forms had been produced by spon-
taneous generation.

Spallanzani. — The epoch-making researches of Spallan-
zani, a fellow-countryman of Redi, were needed to point out
the error in Needham's conclusions. Spallanzani (Fig. 90)
was one of the most eminent men of his time. He was
educated for the church, and, therefore, he is usually known
under the title of Abbe Spallanzani. He did not, however,
actively engage in his churchly offices, but, following an innate
love of natural science and of investigation, devoted himself
to experiments and researches and to teaching. He was first
a professor at Bologna, and afterward at the University of
Pavia. He made many additions to knowledge of the
development and the physiology of organisms, and he was
the first to make use of glass flasks in the experimental study
of the question of the spontaneous generation of life.

Spallanzani thought that the experiments of Needham
had not been conducted with sufficient care and precision;
accordingly, he made use of glass flasks with slender necks
which could be hermetically sealed after the nutrient fluids
had been introduced. The vials which Needham used as
containers were simply corked and sealed with mastic, and
it was by no means certain that the entrance of air after
heating had been prevented; moreover, no record was made
by Needham of the temperature and the time of heating to
which his bottles and fluids had been subjected.

Spallanzani took nutrient fluids, such as the juices of vege-

PASTEUR, KOCH, AND OTHERS

283

tables and meats which had been extracted by boiling, placed
them in clean flasks, the necks of which were hermetically
sealed in flame, and afterward immersed them in boiling
water for three-quarters of an hour, in order to destroy all

Fig. 90. — Lazzaro Spallanzani, i 729-1 799.

germs that might be contained in them. The organic infu-
sions of Spallanzani remained free from change. It was
then, as now, a well-known fact that organic fluids, when
exposed to air, quickly decompose and acquire a bad smell;

284 BIOLOGY AND ITS MAKERS

they soon become turbid, and in a little time a scum is
formed upon their surface. The fluids in the flasks of
Spallanzani remained of the same appearance and consistency
as when they were first introduced into the vessel, and the
obvious conclusion was drawn that microscopic life is not
spontaneously formed within nutrient fluids.

"But Needham was not satisfied with these results, and
with a show of reason maintained that such a prolonged
boiling would destroy not only germs, but the germinative,
or, as he called it, the 'vegetative force' of the infusion
itself. Spallanzani easily disposed of this objection by show-
ing that when the infusions were again exposed to the air,
no matter how severe or prolonged the boiling to which they
had been subjected, the infusoria reappeared. His experi-
ments were made in great numbers, with different infusions,
and were conducted with the utmost care and precision"
(Dunster). It must be confessed, however, that the success
of his experiments was owing largely to the purity of the air
in which he v;orked, the more resistant atmospheric germs
were not present: as Wyman showed, long afterward, that
germs may retain their vitality after being subjected for
several hours to the temperature of boiling water.

Schulze and Schwann. — ^The results of Spallanzani's ex-
periments were published in 1775, and were generally re-
garded by the naturalists of that period as answering in the
negative the question of the spontaneous generation of life.
Doubts began to arise as to the conclusive nature of Spal-
lanzani's experiments, on account of the discoveiy of the part
which oxygen plays in reference to life. The discovery of
oxygen, one of the greatest scientific events of the eighteenth
century, was made by Priestley in 1774. It was soon shown
that oxygen is necessar}^ to all forms of life, and the question
was raised : Had not the boiling of the closed flasks changed
the oxygen so that through the heating process it had lost its

PASTEUR, KOCH, AND OTHERS 285

life-giving properties? This doubt grew until a reexamina-
tion of the question of spontaneous generation became nec-
essary under conditions in which the nutrient fluids were
made accessible to the outside air.

In 1836 Franz Schulze, and, in the following year,
Theodor Schwann, devised experiments to test the question
on this new basis. Schwann is known to us as the founder of
the cell-theory, but we must not confuse Schulze with Max
Schultze, who established the protoplasm doctrine. In the
experiments of Schulze, a flask was arranged containing
nutrient fluids, with a large cork perforated and closely fitted
with bent glass tubes connected on one side with a series of
bulbs in which were placed sulphuric acid and other chemical
substances. An aspirator was attached to the other end of
this system, and air from the outside was sucked into the
flask, passing on its way through the bulbs containing the
chemical substances. The purpose of this was to remove
the floating germs that exist in the air, while the air itself
was shown, through other experiments by Schwann, to re-
main unchanged.

Tyndall says in reference to these experiments: **Here
again the success of Schulze was due to his working in
comparatively pure air, but even in such air his experiment
is a risky one. Germs will pass unwetted and unscathed
through sulphuric acid unless the most special care is taken
to detain them. I have repeatedly failed, by repeating
Schulze's experiments, to obtain his results. Others have
failed likewise. The air passes in bubbles through the
bulbs, and to render the method secure, the passage of the
air must be so slow as to cause the whole of its floating
matter, even to the very core of each bubble, to touch the
surrounding fluid. But if this precaution be observed water
■will he found quite as effectual as sulphuric acid.^^

Schwann's apparatus was similar in construction, except

286 BIOLOGY AND ITS MAKERS

that the bent tube on one side was surrounded by a jacket
of metal and was subjected to a very high temperature while
the air was being drawn through it, the effect being to kill
any floating germs that might exist in the air. Great care
was taken by both experimenters to have their flasks and fluids
thoroughly sterilized, and the results of their experiments were
to show that the nutrient fluids remained uncontaminated.

These experiments proved that there is something in
the atmosphere which, unless it be removed or rendered
inactive, produces life within nutrient fluids, but whether
this something is solid, fluid, or gaseous did not appear
from the experiments. It remained for Helmholtz to show,
as he did in 1843, ^^^^ ^his something will not pass through
a moist animal membrane, and is therefore a solid. The
results so far reached satisfied the minds of scientific men,
and the question of the spontaneous origin of life was.
regarded as having been finally set at rest.

III. The Third Period. Pouchet. — We come now to con-
sider the third historical phase of this question. Although it
had apparently been set at rest, the question was unexpect-
edly opened again in 1859 by the Frenchman Pouchet, the
director of the Natural History Aluseum of Rouen. The
frame of mind which Pouchet brought to his experimental
investigations was fatal to unbiased conclusions: ''When,
by meditation,'''' he says, in the opening paragraph of his book
on Hetero genesis, ''it was evident to me that spontaneous
generation was one of the means employed by nature for the
production of living beings, I applied myself to discover by
what means one could place these phenomena in evidence."
Although he experimented, his case was prejudiced by
metaphysical considerations. He repeated the experiments
of previous observers with opposite results, and therefore he
declared his belief in the falsity of the conclusions of Spal-
lanzani, Schulze, and Schwann.

PASTEUR, KOCH, AND OTHERS 287

He planned and executed one experiment which he sup-
posed was conclusive. In introducing it he said: "The
opponents of spontaneous generation assert that the germs of
microscopic organisms exist in the air, which transports them
to a distance. What, then, will these opponents say if I
succeed in introducing the generation of living organisms,
while substituting artificial air for that of the atmosphere?"

He filled a flask with boiling water and sealed it with great
care. This he inverted over a bath of mercury, thrusting
the neck of the bottle into the mercury. When the water
was cooled, he opened the neck of the bottle, still under the
mercury, and connected it with a chemical retort containing
the constituents for the liberation of oxygen. By heating
the retort, oxygen was driven off from the chemical salts
contained in it, and being a gas, the oxygen passed through
the connecting tube and bubbled up through the water of
the bottle, accumulating at the upper surface, and by pressure
forcing water out of the bottle. After the bottle was about
half filled with oxygen imprisoned above the water, Pouchet
took a pinch of hay that had been heated to a high tempera-
ture in an oven, and with a pair of sterilized forceps pushed
it underneath the mercury and into the mouth of the bottle,
where the hay floated into the water and distributed itself.

He thus produced a hay infusion in contact with pure oxy-
gen, and after a few days this hay infusion was seen to be cloudy
and turbid. It was, in fact, swarming with micro-organisms.
Pouchet pointed with triumphant spirit to the apparently
rigorous way in which his experiment had been carried on:
''Where," said he, ''does this life come from? It can not
come from the water which had been boiled, destroying all
living germs that may have existed in it. It can not come
from the oxygen which was produced at the temperature
of incandescence. It can not have been carried in the hay,
which had been heated for a long period before being intro-

288 BIOLOGY AND ITS MAKERS

duced into the water." He declared that this life was, there-
fore, of spontaneous origin.

The controversy now revived, and waxed warm under the
insistence of Pouchet and his adherents. Finally the Acad-
emy of Sciences, in the hope of bringing it to a conclusion,
appointed a committee to decide upon conflicting claims.

Pasteur. — Pasteur had entered into the investigation of
the subject about i860, and, with wonderful skill and acumen,
was removing all possible grounds for the conclusions of
Pouchet and his followers. In 1864, before a brilliant
audience at the Sorbonne, he repeated the experiment out-
lined above and showed the source of error. In a darkened
room he directed a bright beam of light upon the apparatus,
and his auditors could see in the intense illumination that
the surface of the mercury was covered with dust particles.
Pasteur then showed that when a body was plunged beneath
the mercury, some of these surface granules were carried
with it. In this striking manner Pasteur demonstrated
that particles from the outside had been introduced into the
bottle of w^ater by Pouchet. This, however, is probably not
the only source of the organisms which were developed in
Pouchet's infusions. It is now known that a hay infusion
is very difficult to sterilize by heat, and it is altogether likely
that the infusions used by^ Pouchet were not completely
sterilized.

The investigation of the question requires more critical
methods than was at first supposed, and more factors enter
into its solution than were realized by Spallanzani and
Schwann.

Pasteur demonstrated that the floating particles of the air
contained living germs, by catching them in the meshes of
gun cotton, and then dissolving the cotton with ether and
examining the residue. He also showed that sterilized
organic fluids could be protected by a plug of cotton suffi-

PASTEUR, KOCH, AND OTHERS 289

ciently porous to admit of exchange of air, but matted closely
enough to entangle the floating particles. He showed also
that many of the minute organisms do not require free oxygen
for their life processes, but are able to take the oxygen by
chemical decomposition which they themselves produce from
the nutrient fluids.

Jeffries Wyman, of Harvard College, demonstrated that
some germs are so resistant to heat that they retain their
vitality after several hours of boiling. This fact probably
accounts for the difference in the results that have been
obtained by experimenters. The germs in a resting-stage
are surrounded by a thick protective coat of cellulose,
which becomes softened and broken when they germinate.
On this account more recent experimenters have adopted a
method of discontinuous heating of the nutrient fluid that is
being tested. The fluids are boiled at intervals, so that the
unusually resistant germs are killed after the coating has been
rendered soft, and when they are about to germinate.

After the brilliant researches of Pasteur, the question of
spontaneous germination was once again regarded as having
been answered in the negative; and so it is regarded to-day
by the scientific world. Nevertheless, attempts have been
made from time to time, as by Bastian, of England, in 1872,
to revive it on the old lines.

Tyndall. — John Tyndall (1820-1893), the distinguished
physicist, of London, published, in 1876, the results of his ex-
periments on this question, which, for clearness and ingenuity,
have never been surpassed. For some time he had been
experimenting in the domain of physics with what he called
optically pure air. It was necessary for him to have air from
which the floating particles had been sifted, and it occurred
to him that he might expose nutrient fluids to this optically
pure air, and thus very nicely test ,the question of the
spontaneous origin of life within them.
19

290

BIOLOGY AND ITS MAKERS

He devised a box, or chamber, as shown in Fig. 91,
having in front a large glass window, two small glass win-
dows on the ends, and in the back a little air-tight trap-door.
Through the bottom of this box he had fitted ordinary test

Fig.

91

-Apparatus of Tyndall for Experimenting on Spontaneous
Generation,

tubes of the chemist, with an air-tight surrounding, and on
the top he had inserted some coiled glass tubes, which were
open at both ends and allowed the passage of air in and out
of the box through the tortuous passage. In the middle
of the top of the box was a round piece of rubber. When
he perforated this with a pinhole the elasticity of the rub-

PASTEUR, KOCH, AND OTHERS 291

ber would close the hole again, but it would also admit of
the passage through it of a small glass tube, such as is
called by chemists a "thistle tube." The interior of this
box w^as painted with a sticky substance like glycerin,
in order to retain the floating particles of the air when they
had once settled upon its sides and bottom. The apparatus
having been prepared in this way, was allowed to stand, and
the floating particles settled by their own weight upon
the bottom and sides of the box, so that day by day the
number of floating particles became reduced, and finally all
of them came to rest.

The air now diff"ered from the outside air in having been
purified of all of its floating particles. In order to test the
complete disappearance of all particles. Tyndall threw a
beam of light into the air chamber. He kept his eye in the
darkness for some time in order to increase its sensitiveness ;
then, looking from the front through the glass into the box,
he was able to see any particles that might be floating there.
The floating particles would be brightly illuminated by the
condensed light that he directed into the chamber, and
would become visible. When there was complete darkness
within the chamber, the course of the beam of light was
apparent in the room as it came up to the box and as
it left the box, being seen on account of the reflection from
the floating particles in the air, but it could not be seen
at all within the box. When this condition was reached,
Tyndall had what he called optically pure air, and he was
now ready to introduce the nutrient fluids into his test tubes.
Through a thistle tube, thrust into the rubber diaphragm
above, he was able to bring the mouth of the tube successively
over the different test tubes, and, by pouring different kinds
of fluids from above, he was able to introduce these into
dift'erent test tubes. These fluids consisted of mutton broth,
cf turnip broth, and other decoctions of animal and vegeta-

292 BIOLOGY AND ITS MAKERS

ble matter. It is to be noted that the test tubes were not
corked and consequently that the fluids contained within
them were freely exposed to the optically pure air within the
chamber.

The box was now lifted, and the ends of the tubes extend-
ing below it were thrust into a bath of boiling oil. This set
the fluids into a state of boiling, the purpose being to kill
any germs of life that might be accidentally introduced into
them in the course of their conveyance to the test tubes.
These fluids, exposed freely to the optically pure air within
this chamber, then remained indefinitely free from micro-
organism^s, thus demonstrating that putrescible fluids may
be freely exposed to air from which the floating particles
have been removed, and not show a trace either of spoiling
or of organic life within them.

It might be objected that the continued boiling of the
fluids had produced chemiical changes inimical to hfc, or in
some way destroyed their life-supporting properties; but
after they had remained for months in a perfectly clear state,
Tyndall opened the little door in the back of the box and
closed it at once, thereby admitting some of the floating
particles from the outride air. Within a few days' time the
fluids which previously had remained uncontaminated were
spoiling and teeming with living organisms.

These experim.ents showed that under the conditions of
the experiments no spontaneous origin of life takes place.
But while we must regard the hypothesis of spontaneous
generation as thus having been disproved on an experimental
basis, it is still adhered to from the theoretical standpoint
by many naturalists; and there are also many who think
that life arises spontaneously at the present time in ultra-
microscopic particles. Weismann's hypothetical " biophors,"
too minute for microscopic observation, are supposed to arise
by spontaneous generation. This phase of the question,

PASTEUR, KOCH, AND OTHERS 293

however, not being amenable to scientific tests, is theoretical,
and therefore, so far as the evidence goes, we may safely say
that the spontaneous origin of life under present condi-
tions is unknown.

Practical Applications. — There are, of course, numerous
practical applications of the discovery that the spoiling of
putrescible fluids is due to floating germs that have been
introduced from the air. One illustration is the canning of
meats and fruits, where the object is, by heating, to destroy
all living germs that are distributed through the substance,
and then, by canning, to keep them out. When this is
entirely successful, the preserved vegetables and meats go
uncontaminated. One of the most important and practical
applications came in the recognition (1867) by the English
surgeon Lister that wounds during surgical operations are
poisoned by floating particles in the air or by germs cling-
ing to instruments or the skin of the operator, and that to
render all appHances sterile and, by antiseptic dressings,
completely to prevent the entrance of these bacteria into
surgical wounds, insures their being clean and healthy.
This led to antiseptic surgery, with which the name of Lister
is indissolubly connected.

The Germ-Theory of Disease

The germ-theory of disease is another question of general
bearing, and it will be dealt with briefly here.

After the discovery of bacteria by Leeuwenhoek, in 1687,
some medical men of the time suggested the theory that con-
tagious diseases were due to microscopic forms of life that
passed from the sick to the well. This doctrine of contagium
vivum, when first promulgated, took no firm root, and grad-
ually disappeared. It was not revived until about 1840.
If we attempt briefly to sketch the rise of the germ-theory of

294 BIOLOGY AND ITS MAKERS

disease, we come, then, first to the year 1837, when the
Italian Bassi investigated the disease of silkworms, and
showed that the transmission of that disease was the result
of the passing of minute glittering particles from the sick to
the healthy. Upon the basis of Bassi's observation, the
distinguished anatomist Henle, in 1840, expounded the
theory that all contagious diseases are due to microscopic
germs.

The matter, however, did not receive experimental proof
until 1877, when Pasteur and Robert Koch showed the direct
connection between certain microscopic filaments and the
disease of splenic fever, which attacks sheep and other cattle.
Koch was able to get some of these minute filaments under
the microscope, and to trace upon a warm stage the different
steps in their germination. He saw the spores bud and
produce filamentous forms. He was able to cultivate these
upon a nutrient substance, gelatin, and in this way to obtain
a pure culture of the organism, which is designated under
the term anthrax. He inoculated mice with the pure culture
of anthrax germs, and produced splenic fever in the inocu-
lated forms. He was able to do this through several genera-
tions of mice. In the same year Pasteur showed a similar
connection between splenic fever and the anthrax.

This demonstration of the actual connection between
anthrax and splenic fever formed the first secure foundation
of the germ-theor}' of disease, and this department of inves-
tigation became an important one in general biology. The
pioneer workers who reached the highest position in the de-
velopment of this knowledge are Pasteur, Koch, and Lister.

Veneration of Pasteur. — Pasteur is one of the most con-
spicuous figures of the nineteenth century. The veneration
in which he is held by the French people is shown in the
result of a popular vote, taken in 1907, by which he was
placed at the head of all their notable men. One of the most

Fig. 92. — Louis Pasteur (1822-1895) and his Granddaughter.

296 BIOLOGY AND ITS MAKERS

widely circulated of the French journals — the Peiil Parisien —
appealed to its readers all over the country to vote upon the
relative prominence of great Frenchmen of the last century.
Pasteur was the winner of this interesting contest, having
received 1,338,425 votes of the fifteen millions cast, and rank-
ing above Victor Hugo, who stood second in popular esti-
mation, by more than one hundred thousand votes. This
enviable recognition was won, not by spectacular achieve-
ments in arms or in politics, but by indefatigable industry
in the quiet pursuit of those scientific researches that have
resulted in so much good to the human race.

Personal Qualities. — He should be known also from the
side of his human qualities. He was devotedly attached to
his family, enjoying the close sympathy and assistance of his
wife and his daughter in his scientific struggles, a circum-
stance that aided much in ameliorating the severity of his
labors. His labors, indeed, overstrained his powers, so that
he was smitten by paralysis in 1868, at the age of forty-six,
but with splendid courage he overcame this handicap, and
continued his unremitting work until his death in 1895.

The portrait of Pasteur with his granddaughter (Fig. 92)
gives a touch of personal interest to the investigator and the
contestant upon the field of science. His strong face shows
dignity of purpose and the grim determination which led to
colossal attainments; at the same time it is mellowed by
gentle affection, and contrasts finely with the trusting ex-
pression of the younger face.

Pasteur was born of humble parents in D61e in the Jura,
on December the 27th, 1822. His father was a tanner,
but withal, a man of fine character and stern experience, as
is "shown by the fact that he had fought in the legions
of the First Empire and been decorated on the field of
battle by Napoleon." The filial devotion of Pasteur and his
justifiable pride in his father's military service are shown

PASTEUR, KOCH, AND OTHERS 297

in the dedication of his book, Studies on Fermentation,
published in 1876:

"To the memor}'' of my Father,
Formerly a soldier under tbe First Empire, and Knight of the Legion of

Honor.
The longer I live, the better do I understand the kindness of thy heart

and the superiority of thy judgment.

The efforts which I have devoted to these studies and to those which have

preceded them are the fruits of thy example and of thy counsel.

Desiring to honor these precious recollections, I dedicate this book to thy

memory."

When Pasteur was an infant of two years his parents
removed to the town of Arbois, and here he spent his youth
and received his early education. After a period of indiffer-
ence to study, during which he employed his time chiefly in
fishing and sketching, he settled down to work, and, there-
after, showed boundless energy and enthusiasm.

Pasteur, whom we are to consider as a biologist, won his
first scientific recognition at the age of twenty-five, in chem-
istry and molecular physics. He showed that crystals of
certain tartrates, identical in chemical composition, acted
differently upon polarized light transmitted through them.
He concluded that the differences in optical properties
depended upon a different arrangement of the molecules;
and these studies opened the fascinating field of molecular
physics and physical chemistry.

Pasteur might have remained in this field of investigation,
but his destiny was different. As Tyndall remarked, "In
the investigation of microscopic organisms — the 'infinitely
little,' as Pasteur loved to call them — and their doings in this,
our world, Pasteur found his true vocation. In this broad
field it has been his good fortune to alight upon a crowd of
connected problems of the highest public and scientific
interest, ripe for solution, and requiring for their successful

298 BIOLOGY AND ITS MAKERS

treatment the precise culture and capacities which he has
brought to bear upon them."

In 1857 Pasteur went to Paris as director of scientific
studies in the ficole Normale, having previously been a
professor in Strasburg and in I.ille. From this time on his
energies became more and more absorbed in problems of a
biological nature. It was a momentous year (1857) in the
annals of bacteriology when Pasteur brought convincing
proof that fermentation (then considered chemical in its
nature) was due to the growth of organic life. Again in i860
he demonstrated that both lactic (the souring of milk) and
alcoholic fermentation are due to the growth of microscopic
organisms, and by these researches he developed the
province of biology that has expanded into the science of
bacteriology.

After Pasteur entered the path of investigation of microbes
his progress was by ascending steps; each new problem the
solution of which he undertook seemed of greater importance
than the one just conquered. He was led from the discovery
of microbe action to the application of his knowledge to the
production of antitoxins. In all this he did not follow his
own inclinations so much as his sense of a call to service. In
fact, he always retained a regret that he was not permitted
to perfect his researches on crystallography. At the age of
seventy he said of himself: ''If I have a regret, it is that I did
not follow that route, less rude it seems to me, and which
would have led, I am convinced, to wonderful discoveries.
A sudden turn threw me into the study of fermentation, fer-
mentations set me at diseases, but I am still inconsolable to
think that I have never had the time to go back to my old
subject" (Tarbell).

Although the results of his combined researches form a
succession of triumphs, every point of his doctrines vras the
subject of fierce controversy; no investigations ever met

PASTEUR, KOCH, AND OTHERS 299

with more determined opposition, no investigator ever fought
more strenuously for the estabhshment of each new truth.

He went from the study of the diseases of wines (1865)
to the investigation (i 865-1 868) of the silkworm plague
which had well-nigh crushed the silk industry of his country.
The result was the saving of millions of francs annually to
the people of France.

His Supreme Service. — He then entered upon his chief
services to humanity — the application of his discoveries to
the cure and prevention of diseases. By making a succession
of pure cultures of a disease-producing virus, he was able to
attenuate it to any desired degree, and thereby to create a
vaccinating form of the virus capable of causing a mild affec-
tion of the disease. The injection of this attenuated virus
secured immunity from future attacks. The efficacy of this
form of inoculation was first proved for the disease of fowl
cholera, and then came the clear demonstration (1881) that
the vaccine was effective against the splenic fever of cattle.
Crowning this series of discoveries came the use of inoculation
(1885) to prevent the development of hydrophobia in one
bitten by a mad dog.

The Pasteur Institute. — ^The time had now come for the
establishment of an institute, not alone for the treatment of
hydrophobia, but also for the scientific study of means to
control other diseases, as diphtheria, typhoid, tuberculosis,
etc. A movement was set on foot for a popular subscription
to meet this need. The response to this call on the part of
the common people was gratifying. "The extraordinary en-
thusiasm which accompanied the foundation of this great
institution has certainly not been equaled in our time.
Considerable sums of money were subscribed in foreign coun-
tries, while contributions poured in from every part of France.
Even the inhabitants of obscure little towns and villages
organized f^tes, and clubbed together to send their small

300 BIOLOGY AND ITS MAKERS

gifts " (Franckland). The total sum subscribed on the date
of the opening ceremony amounted to 3,586,680 francs.

The institute was formally opened on November i4t'h,
1888, with impressive ceremonies presided over by the
President of the Republic of France. The establishment
of this institute was an event of great scientific importance.
Here, within the first decade of its existence, were success-
fully treated more than twenty thousand cases of hydrophobia.
Here has been discovered by Roux the antitoxin for diph-
theria, and here have been established the principles of inoc-
ulation against the bubonic plague, against lockjaw, against
tuberculosis and other maladies, and of the recent microbe
inoculations of Wright of London. More than thirty
*' Pasteur institutes," with aims similar to the parent institu-
tion, have been established in different parts of the civilized
world.

Pasteur died in 1895, greatly honored by the whole world.
On Saturday, October 5th of that year, a national funeral
was conducted in the Church of Notre-Dame, which was
attended by the representatives of the state and of numerous
scientific bodies and learned societies.

Koch. — ^Robert Koch (Fig. 93) was born in 1843, ^^^ for
several years before his death, in 19 10, he was the Director
of the Institute for Infectious Diseases in Berlin. His studies
have been mainly those of a medical man, and have been
crowned with remarkable success. In 1881 he discovered
the germ of tuberculosis, in 1883 the germ that produces
Asiatic cholera, and since that time his name has been con-
nected with a number of remarkable discoveries that are of
continuous practical application in the science of medicine.

Koch, with the rigorous scientific spirit for which he is
noteworthy, established four necessary links in the chain
of evidence to show that a particular organism is connected
with a particular disease. These four postulates of Koch are :

PASTEUR, KOCH, AND OTHERS

301

First, that a microscopic organism of a particular type should
be found in great abundance in the blood and the tissue of the
sick animal; second, that a pure culture should be made of
the suspected organism; third, that this pure culture, when
introduced into the body of another animal, should produce

Fig. 93. — Robert Koch, 1843-1910.

the disease; and, fourth, that in the blood and tissues of that
animal there should be found quantities of the particular
organism that is suspected of producing the disease. In the
case of some diseases this entire chain of evidence has been
established ; but in others, such as cholera and typhoid fever,
the last steps have not been completed, for the reason that the

302 BIOLOGY AND ITS MAKERS

animals experimented upon, namely, guinea-pigs, rabbits,
and mice, are not susceptible to these diseases.

Lister. — The other member of the great triumvirate of
bacteriology. Sir Joseph Lister (Fig. 94), was born in 1827
and lived until Feby. 11, 191 2; he was successively professor

Fig. 94. — Sir Joseph Lister, 182 7-19 12.

of surgery in the universities of Glasgow (i860) and of Edin-
burgh (1869), and in King's College, London (1877). His
practical apphcation of the germ-theory introduced aseptic
methods into surgery and completely revolutionized that
field. This was in 1867. In an address given that year be-
fore the British Medical Association in Dublin, he said:
"When it had been shown by the researches of Pasteur that

PASTEUR, KOCH, AND OTHERS 303

the septic property of the atmosphere depended, not on oxy-
gen or any gaseous constituent, but on minute organisms
suspended in it, which owed their energy to their vitality, it
occurred to me that decomposition in the injured part might
be avoided without excluding the air, by applying as a dress-
ing some material capable of destroying the life of the float-
ing particles." At first he used carbolic acid for this purpose.
*'The wards of which he had charge in the Glasgow Infirm-
ary were especially affected by gangrene, but in a short time
became the healthiest in the world; while other wards sepa-
rated by a passageway retained their infection." The
method of Lister has been universally adopted, and at the
same time has been greatly extended and improved.

The question of immunity, i.e., the reason why after hav-
ing had certain contagious diseases one is rendered immune,
is of very great interest, but is of medical bearing, and
therefore is not dealt with here.

Schaudinn. — ^During recent years remarkable advances
have been made in the study of protozoa that are connected
with human and animal diseases, and no single observer has
contributed more eminently to these advances than Fritz
Robert Schaudinn, 1871-1906 (Fig. 94a). He made impor-
tant discoveries and opened up new lines of investigation
that are full of promise. After studies on f oramenif era ( 1 894) ,
and nuclear division in other protozoa (1896), he was drawn
to the study of pathogenic protozoa, the life history of which
he followed with conspicuous success. After unravelling
the complexities of the life-cycle in certain coccidia, parasitic
in the mole, he traced in the human blood corpuscles the
different stages of the carriers of malaria.

In 1901, under the auspices of the Imperial Health Bureau
(Kaiserl-Gesundheitsamtes) of Berlin, he went to the station
at Rovigno, and thereafter to the end of his life, he devoted

304

BIOLOGY AND ITS MAKERS

his energies to the study of pathogenic protozoa and of some
bacteria. He observed the successive stages of generation
of some micro-organisms of birds and other animals, and
in 1905, he clearly demonstrated the spirochaete of syphilis
{Treponema pallida) the existence of which had previously
been made known by Siegel.

Fig. 94a. — Fritz Schaudinn, 1871-1906.

His researches were thorough as well as brilliant, and it is
largely owing to his influence that the importance of proto-
zoology is recognized as a special division of biological study.

Bacteria and Nitrates. — One further illustration of the
connection between bacteria and practical affairs may be
mentioned. It is well known that animals are dependent
upon plants, and that plants in the manufacture of protoplasm
make use of certain nitrites and nitrates which they obtain

PASTEUR, KOCH, AND OTHERS 305

from the soil. Now, the source of these nitrites and nitrates
is very interesting. In animals the final products of broken-
down protoplasm are carbon dioxide, water, and a nitrog-
enous substance called urea. These products are called
excretory products. The animal machine is unable to utilize
the energy which exists in the form of potential energy in
these substances, and they are removed from the body.

The history of nitrogenous substance is the one which at
present interests us the most. Entering the soil, it is there
acted upon by bacteria residing in the soil, these bacteria
possessing the power of making use of the lowest residuum
of energy left in the nitrogenous substance. They cause the
nitrogen and the hydrogen to unite with oxygen in such a way
that there are produced nitrous and nitric acids, and from
these two acids, through chemical action, result the nitrites and
the nitrates. These substances are then utilized by the plant
in the manufacture of protoplasm, and the plant is fed upon
by animal organisms, so that a direct relationship is estab-
lished between these lower forms of life and the higher plant
and animal series; a relationship that is not only interesting,
but that helps to throw an important side-light upon the
general nature of vital activities, their kind and their reach.
In addition to the soil bacteria mentioned above, there
are others that form association with the rootlets of certain
plants and possess the power of fixing free nitrogen from
the air.

The nitrifying bacteria, are, of course, of great importance
to the farmer and the agriculturist.

It is not our purpose, however, to trace the different
phases of the subject of bacteriology to their conclusions, but
rather to give a picture of the historical development of this
subject as related to the broader one of general biology.

CHAPTER XIV

HEREDITY AND GERMINAL CONTINUITY—
MENDEL, GALTON, WEISMANN

It is a matter of common observation that in the living
world like tends to produce like. The offspring of plants,
as well as of animals, resembles the parent, and among all
organisms endowed with mind, the mental as well as the
physical qualities are inherited. This is a simple statement
of the fact of heredity, but the scientific study of inheritance
involves deep-seated biological questions that emerged late
in the nineteenth century, and the subject is still in its
infancy.

In investigating this question, we need first, if possible,
to locate the bearers of hereditary qualities within the physical
substance that connects one generation with the next; then,
to study their behavior during the transmission of life in order
to account for the inheritance of both maternal and paternal
qualities; and, lastly, to determine whether or not transiently
acquired characteristics are inherited.

Hereditary Qualities in the Germinal Elements. — When
we take into consideration the fact established for all animals
and plants (setting aside cases of budding and the division
of unicellular organisms), that the only substance that passes
from one generation to another is the egg and the sperm in
animals, and their representatives in plants, we see that the
first question is narrowed to these bodies. If all hereditary
qualities are carried in the egg and the sperm — as it seems
they must be — then it follows that these germinal elements,

306

HEREDITY AND GERMINAL CONTINUITY 307

although microscopic in size, have a very complex organiza-
tion. The discovery of this organization must depend upon
microscopic examination. Knowledge regarding the physical
basis of heredity has been greatly advanced by critical studies
of cells under the microscope and by the application of ex-
perimental methods, while other phases of the problems of
inheritance have been elucidated by the analysis of statistics
regarding hereditary transmissions. The whole question,
however, is so recent that a clear formulation of the direction
of the main currents of progress will be more helpful than
any attempt to estimate critically the underlying principles.

Early Theories. — There were speculations regarding the
nature of inheritance in ancient and mediaeval times. To
mention any of them prior to the eighteenth century would
serve no useful purpose, since they were vague and did not
form the foundation upon which the modern theories were
built. The controversies over pre-formation and epigenesis
(see Chapter X) of the eighteenth century embodied some
ideas that have been revived. The recent conclusion that
there is in the germinal elements an inherited organization
of great complexity which conditions inheritance seems, at
first, to be a return to the doctrine of pre-formation, but closer
examination shows that there is merely a general resemblance /
between the ideas expressed by Haller, Bonnet, and philos-
ophers of their time and those current at the present time.
Inherited organization, as now understood, is founded on
the idea of germinal continuity and is vastly different from
the old theory of pre-formation. The meaning of epigenesis,
as expressed by Wolff, has also been modified to include the
conception of pre-localization of hereditary qualities w^ithin
particular parts of the egg. It has come now to mean that
development is a process of difi"erentiation of certain qualities
already laid down in the germinal elements.

Darwin's Theory of Pangenesis. — In attempting to

3o8 BIOLOGY AND ITS MAKERS

account for heredity, Darwin saw clearly the necessity of
providing some means of getting all hereditary qualities com-
bined within the egg and the sperm. Accordingly he orig-
inated his provisional theory of pangenesis. Keeping in mind
the fact that all organism.s begin their lives in the condition
of single cells, the idea of inheritance through these micro-
scopic particles becomes difficult to understand. How is it
possible to conceive of all the hereditary qualities being con-
tained within the microscopic germ of the future being?
Darwin supposed that very minute particles, which he called
gemmules, were set free from all the cells in the body, those
of the muscular system, of the nervous system, of the bony
tissues, and of all other tissues contributing their part. These
liberated gemmules were supposed to be carried by the cir-
culation and ultimately to be aggregated within the germinal
elements (ovum and sperm). Thus the germinal elements
would be a composite of substances derived from all organs
and all tissues.

With this conception of the blending of the parental
qualities within the germinal elements we can conceive how
inheritance would be possible and how there might be in-
cluded in the egg and the sperm a representative in material
substance of all the qualities of the parents. Since develop-
ment begins in a fertilized ovum, this complex would contain
minute particles derived from every part of the bodies of
both parents, which by growth would give rise to new tissues,
all of them containing representatives of the tissues of the
parent form.

Theory of Pangenesis Replaced by that of Germinal Con-
tinuity.— This theory of Darwin served as the basis for other
theories founded upon the conception of the existence of pan-
gens ; and although the modifications of Spencer, Brooks, and
others were important, it is not necessary to indicate them in
detail in order to understand what is to follow. The various

HEREDITY AND GERMINAL CONTINUITY 309

theories founded upon the idea of pangens were destined to
be replaced by others founded on the conception of geminal
continuity — the central idea in nineteenth-century biology.

The four chief steps which have led to the advancement
of the knowledge of heredity, as suggested by Thomson, are
as follows: " (a) The exposition of the doctrine of germinal
continuity, (b) More precise investigation of the material
basis of inheritance, (c) Suspicions regarding the inherit-
ance of acquired characteristics, (d) Application of statis-
tical methods which have led to the formulation of the law
of ancestral heredity." We shall take these up in order.

Exposition of the Doctrine of Germinal Continuity. —
From parent to offspring there passes some hereditary sub-
stance; although small in amount, it is the only living thread
that connects one generation with another. It thus appears
that there enters into th-e building of the body of a new organ-
ism some of the actual substance of both parents, and that
this transmitted substance must be the bearer of hereditary
qualities. Does it also contain some characteristics inherited
from grandparents and previous generations? If so, how
far back in the history of the race does unbroken continuity
extend ?

Briefly stated, genetic continuity means that the ovum
and its fertilizing agent are derived by continuous cell-lineage
from the fertilized ovum of previous generations, extending
back to the beginning of life. The first clear exposition of
this theory occurs in the classical work of Virchow on Cellular
Pathology, pubhshed in 1858. Virchow (1821-1902), the
distinguished professor of the University of Berlin, has al-
ready been spoken of in connection with the development
of histology. He took the step of overthrowing the theory
of free cell-formation, and replacing it by the doctrine of
cell- succession. According to the theory of Schleiden and
Schwann, cells arose from a blastema by a condensation of

3IO BIOLOGY AND ITS MAKERS

matter around a nucleus, and the medical men prior to 1858
believed in free cell-formation within a matrix of secreted
or excreted substance. This doctrine was held with tenacity
especially for pathological growths. Virchow demonstrated,
however, that there is a continuity of living substance in all
growths — that cells, both in health and in disease, arise only
by the growth and division of previously existing living cells;
and to express this truth he coined the formula ^^ omnis
cellula e cellula.^' Manifestly it vras necessary to establish
this law of cell- succession before any idea of germinal con-
tinuity could prevail. Virchow' s work in this connection
is of undying value.

When applied to inheritance the idea of the continuity of
living substance leads to making a distinction between germ-
cells and body-cells. This had been done before the obser-
vations of Virchow made their separation of great theoretical
value. Richard Owen, in 1849, pointed out certain differ-
ences between the body-cells and the germinal elements,
but he did not follow up the distinction which he made.
Haeckel's General Morphology, published in 1866, forecasts
the idea also, and in 1878 Jaeger made use of the phrase
"continuity of the germ protoplasm." Other suggestions
and modifications led to the clear expression by Nussbaum,
about 1875, that the germinal substance was continued by
unbroken generations from the past, and is the particular
substance in which all hereditary qualities are included.
But the conception finds its fullest expression in the work
of Weismann.

Weismann's explanation of heredity is at first sight
relatively simple. In reply to the question, "Why is the
offspring like the parent ? " he says, "Because it is composed
of some of the same stuff." In other words, there has been
unbroken germinal continuity between generations. His idea
of germinal continuity, i.e., unbroken continuity, through all

HEREDITY AND GERMINAL CONTINUITY 311

time, of the germinal substance, is a conception of very great
extent, and now underlies all discussion of heredity.

In order to comprehend it, we must first distinguish
between the germ-cells and the body-cells. Weismann
regards the body, composed of its many cells, as a derivative
that becomes simply a vehicle for the germ-cells. Owen's
distinction between germ-cells and body-cells, made in 1849,
was not of much importance, but in the theory of Weismann
it is of vital significance. The germ-cells are the particular
ones which carry forward from generation to generation the
life of the individual. The body-cells are not inherited di-
rectly, but in the transmission of life the germ-cells pass to
the succeeding generation, and they in turn have been inher-
ited from the previous generation, and, therefore, we have
the phenomenon of an unbroken connection with all previous
generations.

When the full significance of this conception comes to us,
we see why the germ-cells have an inherited organization of
remarkable complexity. This germinal substance embodies
all the past history of the living, impressionable protoplasm,
which has had an unbroken series of generations. During
all time it has been subjected to the molding influence of
external circumstances to which it has responded, so that
the summation of its experiences becomes in some way
embedded within its material substance. Thus we have
the germinal elements possessing an inherited organization
made up of all the previous experiences of the protoplasm,
some of which naturally are much more dominant than the
others.

We have seen that this idea was not first expressed by
Weismann; it was a modification of the views of Nussbaum
and Hertwig. While it was not his individually, his con-
clusions were apparently reached independently. This idea
was in the intellectual atmosphere of the times. Several

312 BIOLOGY AND ITS MAKERS

investigators reached their conclusions independently, al-
though there is great similarity between them. Although the
credit for the first formulation of the law of germinal con-
tinuity does not belong to Weismann, that of the greatest
elaboration of it does. This doctrine of germinal continuity
is now so firmly embedded in biological ideas of inheritance
and the evolution of animal life that we may say it has become
the corner-stone of modern biology.

The conclusion reached — that the hereditary substance is
the germ-plasm — is merely prehminary ; the question remains,
Is the germ-plasm homogeneous and endowed equally in all
parts with a mixture of hereditary qualities ? This leads
to the second step.

The More Precise Investigation of the Material Basis of
Inheritance. — The application of the microscope to critical
studies of the structure of the germ-plasm has brought
important results which merge with the development of the
idea of germinal continuity. Can we by actual observation
determine the particular part of the protoplasmic substance
that carries the hereditary qualities? The earliest answer
to this question was that the protoplasm, being the living
substance, was the bearer of heredity. But close analysis
of the behavior of the nucleus during development led,
about 1875, to the idea that the liereditary qualities are located
within the nucleus of the cell.

This idea, promulgated by Fol, Koelliker, and Oskar
Hertwig, narrowed the attention of students of heredity
from the general protoplasmic contents of the cell to the
nucleus. Later investigations show that this restriction was,
in a measure, right. The nucleus takes an active part
during cell-division, and it was very natural to reach the
conclusion that it is the particular bearer of hereditary
substance. But, in 1883, Van Beneden and Boveri made
the discovery that within the nucleus are certain dis-

HEREDITY AND GERMINAL CONTINUITY 313

tinct little rod-like bodies which make their appearance
during cell-division. These little bodies, inasmuch as they
stain very deeply with the dyes used in microscopic re-
search, are called chromosomes. And continued investigation
brought out the astounding fact that, although the number of
chromosomes vary in different animals (commonly from two
to twenty-four), they are of the same number in all the cells
of any particular animal or plant. These chromosomes are
regarded as the bearers of heredity, and their behavior during
fertilization and development has been followed with great
care.

Brilliant studies of the formation of the egg have
shown that the egg nucleus, in the process of becoming
mature, surrenders one-half its number of chromosomes; it
approaches the surface of the egg and undergoes division,
squeezing out one-half of its substance in the form of a polar
globule; and this process is once repeated.* The formation
of polar globules is accompanied by a noteworthy process of
reduction in the number of chromosomes, so that when the
egg nucleus has reached its mature condition it contains only
one-half the number of chromosomes characteristic of the
species, and will not ordinarily undergo development without
fertilization.

The precise steps in the formation of the sperm have also
been studied, and it has been determined that a parallel
series of changes occur. The sperm, when it is fully formed,
contains also one-half the number of chromosomes charac-
teristic of the species. Now, egg and sperm are the two ger-
minal elements which unite in development. Fertilization
takes place by the union of sperm and egg, and inasmuch
as the nuclei of each of these structures contain one-half of
the number of chromosomes characteristic of the species,

* There are a few exceptions to this rule, as in the eggs of plant-lice,
etc., in which a single polar globule is produced.

314 BIOLOGY AND ITS MAKERS

their union in fertilization results in the restoration of the
original number of chromosomes. The fertilized ovum is
the starting-point of a new organism, and from the method
of its fertilization it appears that the parental qualities are
passed along to the cells of every tissue.

The complex mechanism exhibited in the nucleus during
segmentation is very wonderful. The fertilized ovum begins
to divide, the nucleus passing through a series of complicated
changes whereby its chromosomes undergo a lengthwise
division — a division that secures an equable partition of the
substance of which they are composed. With each successive
division, this complicated process is repeated, and the many
cells, arising from continued segmentation of the original cell,
contain nuclei in which are embedded descendants of the
chromosomes in unbroken succession. Moreover, since these
chromosomes are bi-parental, we can readily understand that
every cell in the body carries both maternal and paternal
qualities.

The careful analysis of the various changes within the
nuclei of the egg proves to be the key to some of the central
questions of heredity. We see the force of the point which
was made in a previous chapter, that inheritance is in the
long run a cellular study, and we see in a new light the im-
portance of the doctrine of germinal continuity. This con-
ception, in fact, elucidates the general problem of inheritance
in a way in which it has never been elucidated by any other
means.

For some time the attention of investigators was concen-
trated upon the nucleus and the chromosomics, but it is now
necessary to admit that the basis of some structures is dis-
coverable within the cytoplasm that surrounds the nucleus.
Experimental observations (Conklin, Lillie, Wilson) have
shown the existence of particular areas within the apparently
simple substance of the egg, areas which are definitely related

HEREDITY AND GERMINAL CONTINUITY 315

to the development of particular parts of the embryo. The
removal of any one of these pre-localized areas prevents the
development of the part with which it is genetically related.
Researches of this kind, necessitating great ingenuity in
method and great talents in the observers, are widening the
field of observation upon the phenomena of heredity.

The Inheritance of Acquired Characters. — The belief in
the inheritance of acquired characteristics was generally
accepted up to the middle of the nineteenth century, but the
reaction against it started by Galton and others has assumed
great proportions. Discussions in this Hne have been carried
on extensively, and frequently in the spirit of great partizan-
ship. These discussions cluster very much about the name
and the work of Weismann, the man who has consistently
stood against the idea of the inheritance of acquired charac-
ters. More in reference to this phase of the question is given
in the chapter dealing with Weismann's theory of evolution
(see p. 398). Wherever the truth may lie, the discussions
regarding the inheritance of acquired characteristics pro-
voked by Weismann's theoretical considerations, have re-
sulted in stimulating experiment and research, and have,
therefore, been beneficial to the advance of science. n

The Application of Experimental and Statistical Methods
to the Study of Heredity. Mendel. — The earliest experi-
mental investigations of heredity were conducted with plants,
and the first epoch-making results were those of Gregor Men-
del (182 2-1884) (Fig. 95), a monk, and later abbot, of an
Augustinian monastery at Brunn, Austria. In the garden
of the monastery, for eight years before pubhshing his re-
sults, he made experiments on the inheritance of individual
(or unit) characters in twenty-two varieties of garden peas.
Selecting certain constant and obvious characters, as color
and form of seeds, length of stem, etc., he proceeded to cross
these pure races, thus producing hybrids, and, thereafter,

3i6

BIOLOGY AND ITS MAKERS

to observe the results of self-fertilization among the hybrids.
The hybrids were produced by removing the unripe sta-
mens of certain flowers and later fertilizing them by ripe
pollen from another pure breed having a contrasting charac-
ter. The results showed that only one of a pair of unit

Fig. 95. — Gregor Mendel, 1822-1884.
Permission of Professor Bateson.

characters appeared in the hybrids, while the other contrast-
ing character lay dormant. Thus, in crossing a yellow-seeded
with a green-seeded pea, the hybrid generation showed only
yellow seeds. The character impressing itself on the entire
progeny was called dominant, while the other that was held
in abeyance was designated recessive. That the recessive

HEREDITY AND GERMINAL CONTINUITY 317

color was not blotted out was clearly demonstrated by allow-
ing the hybrid generation to develop by self-fertilization.
Under these circumstances a most interesting result was at-
tained. The filial generation, derived by self-fertilization
among the hybrids, produced plants with yellow and green
seeds, but in the ratio of three of the yellow to one of the
green. All of the green-seeded individuals and one-third of
the yellow proved to breed true, while the remaining two-
thirds of yellow-seeded plants, when self-fertilized, produced
yellow and green seeds in the ratio of three to one. Subse-
quent breedings gave an unending series of results similar
to those of the first filial generation. This great principle
of alternative inheritance was exhibited throughout the ex-
tensive experiments of Mendel, and it is now recognized
as one of the great biological discoveries of the nineteenth
century. Mr. R. C. Punnett gives (1905) a remarkably clear
and terse statement of the facts as follows: ''Whenever there
occurs a pair of differentiating characters, of which one is
dominant to the other, three possibilities exist: there are
recessives which always breed true to the recessive character;
there are dominants which breed true to the dominant char-
acter, and are therefore pure; and thirdly, there are domi-
nants which may be called impure, and which on self-fertiliza-
tion (or in breeding, where the sexes are separate) give both
dominant and recessive forms in the fixed proportion of three
of the former to one of the latter."

The results of Mendel's experiments are the consequence
of the fact that the germ-cells retain their purity with respect
to unit characters. That is, in the combination of germ-cells
by cross-breeding, the hereditary qualities do not lose their
individuality — they are mixed but not blended. When the
germinal elements are formed in these hybrid plants two
classes of germ-cells will arise in equal number, one class
carrying the dominant, and the other the recessive quality.

3l8 BIOLOGY AND ITS MAKERS

Chance combinations of these germ-cells will yield on the
average, one union of dominant with dominant, one union of
recessive with recessive, and two combinations in which
dominant and recessive are united. In the latter instance the
dominant will be the visible character, the recessive, though
present, being invisible. This segregation of the gametes
into two sets of ''pure" gametes was recognized by Mendel
in an attempted theoretical explanation of his observed facts,
and, in view of the state of knowledge at the time, showed
remarkable analytical ability.

Mendel's papers were published in 1866 and 1867 in the
Proceedings of the Natural History Society of Briinn, but
their importance was overlooked for nearly thirty-five years.
The periodical in which they appeared was not widely known,
and moreover, the minds of naturalists at that time were
largely occupied with the questions of organic evolution
raised through the pubHcations of Darwin. In the year
1900, however, the great principle of heredity worked out
by Mendel was independently re-discovered by the botanists
DeVries, Torrens, and Tschermak. By searching the htera-
ture for anticipations of their results, the unrecognized papers
of Mendel were brought to light and made generally known
to the scientific world.

Since 1900, extensive experiments by Bateson and others
have served to confirm and extend Mendel's discovery. In
the United States the experiments of Davenport and Castle
on inheritance in poultry, the inheritance of fur in guinea-pigs,
of erectness of ears of rabbits, etc., as well as the experimental
work of others, has extended our knowledge of Mendelian
inheritance. The combined work on inheritance in animals
and plants of all observers has so thoroughly supported
Mendel's conclusions, that the principle of alternative in-
heritance is commonly spoken of as Mendel's law.

Rank of MendePs Discovery. — The discovery by Mendel

HEREDITY AND GERMINAL CONTINUITY 319

of alternative inheritance will rank as one of the greatest
discoveries in the study of heredity. The fact that in cross-
breeding the parental qualities are not blended, but that they
retain their individuahty in the offspring, has many possible
practical applications both in horticulture and in the breed-
ing of animals. The germ-cells of the hybrids have the domi-
nant and the recessive characters about equally divided; this
will appear in the progeny of the second generation, and the
races, when once separated, may be made to breed true.

Mendel's name was not recognized as a prominent one
in the annals of biological history until the re-discovery of his
law in 1900; but now he is accorded high rank.

Galton. — Francis Galton, by directing attention to the
inheritance of individual characters made the subject of
heredity manageable. Previously, hereditary traits had been
considered in their entirety, and the resemblances and differ-
ences of parents and their offspring had been averaged.
This method was too diffuse, since no one could distinguish
sharply among the multiplicity of characters, and it was
a great forward step when Galton began to study hereditary
characters separately. ''At the same time that Galton was
thus laying the foundation for a scientific study of heredity
by dealing with characters separately, another and even
greater student of heredity, Gregor Mendel, was doing the
same thing in his experiments with garden peas. But inas-
much as Mendel's work remained practically unknown for
many years, Galton has been rightly recognized as the founder
of the scientific study of heredity" (Conklin, 1915).

Galton, 182 2-19 1 1 (Fig. 96), was the grandson of Doctor
Erasmus Darwin and the half cousin of Charles. After pub-
lishing books on his travels in Africa, he began the experi-
mental study of heredity and, in 187 1, he read before the
Royal Society of London a paper on Pangenesis, in which he
departed from that theory as developed by Darwin. The

320 BIOLOGY AND ITS MAKERS

observations upon which he based his conclusions were made
upon the transfusion of blood in rabbits and their after-
breeding. He studied the inheritance of stature, and other

Fig. 96. — Francis Galton, 1822-1911.

characteristics, in human families, and the inheritance of
spots on the coat of certain hounds, and was led to formulate
a law of ancestral inheritance which received its clearest ex-
pression in his book, Natural Inheritance, published in 1889.

He undertook to determine the proportion of heritage
that is, on the average, contributed by each parent, grand-

HEREDITY AND GERMINAL CONTINUITY 321

parent, etc., and arrived at the following conclusions: "The
parents together contribute one-half the total heritage, the
four grandparents together one-fourth, the eight great-grand-
parents one-sixteenth, and all the remainder of the ancestry
one-sixteenth."

Karl Pearson has investigated this law of ancestral inher-
itance. He substantiates the law in its principle, but modifies
slightly the mathematical expression of it.

This field of research, which involves measurements and
mathematics and the handling of large bodies of statistics,
has been considerably cultivated, so that there is in existence
in England a journal devoted exclusively to biometrics, which
is edited by Karl Pearson, and is entitled Biometrika.

The whole subject of heredity is undergoing a thorough
revision. What seems to be most needed at the present time
is more exact experimentation, carried through several gen-
erations, together with more searching investigations into
the microscopical constitution of egg and sperm, and close
analysis of just what takes place during fertilization and the
early stages of the development of the individual. Experi-
ments are being conducted on an extended scale in endowed
institutions. There is notably in this country, established
under the Carnegie Institution, a station for experimental
evolution, at Cold Spring Harbor, New York, of which C. B.
Davenport is director. Other experimental stations in Eng-
land and on the Continent have been established, and we
are to expect as the result of coordinated and continuous
experimental work many substantial contributions to the
knowledge of inheritance.

CHAPTER XV
THE SCIENCE OF FOSSIL REMAINS

It gradually dawned on the minds of men that the crust
of the earth is hke a gigantic mausoleum, containing within it
the remains of numerous and varied forms of life that for-
merly existed upon the surface of the earth. The evidence
is clear that untold generations of hving forms, now pre-
served as fossils, inhabited the earth, disported themselves,
and passed away long before the advent of man. The knowl-
edge of this fossil life, on account of its great diversity, is
an essential part of biology, and all the more so from the
circumstance that many forms of life, remains of which
are exhibited in the rocks, have long since become extinct.
No history of biology would be complete without an account
of the rise and progress of that department of biology which
deals w^ith fossil remains.

It has been determined by collecting and systematically
studying the remains of this ancient life that they bear testi-
mony to a long, unbroken history in which the forms of both
animals and plants have been greatly altered. The more
ancient remains are simple in structure, and form with the
later ones, a series that exhibits a gradually increasing com-
plexity of structure. The study of the fossil series has
brought about a very great extension of our knowledge
regarding the age of the world and of the conditions under
which life was evolved.

Strange Views Regarding Fossils. — But this state of our
knowledge was a long time coming, and in the development

322

SCIENXE OF FOSSIL REMAINS 323

of the subject we can recognize several distinct epochs, ''well-
marked by prominent features, but like all stages of intellec-
tual growth, without definite boundaries." Fossils were
known to the ancients, and by some of the foremost philos-
ophers of Greece were understood to be the remains of
animals and plants. After the revival of learning, however,
lively controversies arose as to their nature and their meaning.

Some of the fantastic ideas that were entertained regarding
the nature of fossil remains may be indicated. The fossils
were declared by many to be freaks of nature; others main-
tained that they were the results of spontaneous generation,
and were produced by the plastic forces of nature within the
rocks in which they were found embedded. Another opinion
expressed was that they were generated by fermentations.
As the history of intellectual development shows, the mind
has ever seemed benumbed in the face of phenomena that
are completely misconceived ; mystical explanations have ac-
cordingly been devised to account for them. Some of the
pious persons of that period declared that fossils had been
made and distributed by the Creator in pursuance of a plan
beyond our comprehension. Another droll opinion expressed
was that the Creator in His wisdom had introduced fossil
forms into the rocks in order that they should be a source of
confusion to the race of geologists that was later to arise.

And still another fantastic conception suggested that the
fossils were the original molds used by the Creator in form-
ing different varieties of animals and plants, some of which
had been used and others discarded. It was supposed that
in preparing for the creation of life He experimented and
discarded some of His earliest attempts; and that fossils
represented these discarded molds and also, perhaps, some
that had been used in fashioning the created forms.

When large bones, as of fossil elephants, began to be
exhumed, they became for the most part the objects of stupid

324 BIOLOGY AND ITS MAKERS

wonder. The passage in the Scriptures was pointed out,
that "there were giants in those days," and the bones were
taken to be evidences of the former existence of giants. The
opinions expressed regarding the fossil bones were varied and
fantastic, "some saying that they were rained from Heaven,
others saying that they were the gigantic Hmbs of the ancient
patriarchs, men who were beHeved to be tall because they
were known to be old." Following out this idea, "Henrion
in 17 18 published a work in which he assigned to Adam a
height of 123 feet 9 inches, Noah being 20 feet shorter, and
so on."

Determination of the Nature of Fossils.— In due course
it came to be recognized that fossils were the remains of forms
that had been alive during earlier periods of time; but in
reaching this position there was continual controversy. Ob-
jections were especially vigorous from theological quarters,
since such a conclusion was deemed to be contradictory to
the Scriptures. The true nature of fossils had been clearly
perceived by Leonardo da Vinci (1452-15 19) and certain
others in the sixteenth century.

The work, however, that approached more nearly to sci-
entific demonstration was that of Steno (163 8- 1686), a
Dane who migrated to Italy and became the court physician
to the dukes of Tuscany. He was a versatile man who had
laid fast hold upon the new learning of his day. Eminent
as anatomist, physiologist, and physician, with his ever
active mind he undertook to encompass all learning. It is
interesting that Steno — or Stensen — after being passionately
devoted to science, became equally devoted to religion and
theology, and, forsaking all scientific pursuits, took orders
and returned to his native country with the title of bishop.
Here he worked in the service of humanity and religion to
the end of his life.

In reference to his work in geology, his conclusions

SCIENCE OF FOSSIL REMAINS 325

regarding fossils (1669) were based on the dissection of the
head of a shark, by which means he showed an almost exact
correspondence between certain glossy fossils and the teeth
of living sharks. He applied his reasoning, that like effects
imply Hke causes, to all manner of fossils, and clearly estab-
lished the point that they should be regarded as the remains
of animals and plants. The method of investigation prac-
ticed by Steno was that ''which has consciously or uncon-
sciously guided the researches of palaeontologists ever since."

Although his conclusions were well supported, they did not
completely overthrow the opposing views, and become a fixed
basis in geology. When, at the close of the eighteenth cen-
tury and the beginning of the nineteenth, fossil remains were
being exhumed in great quantities in the Paris basin, Cuvier,
the great French naturalist, reestablished the doctrine that
fossils are the remains of ancient life. An account of this
will be given presently, and in the mean time we shall go on
with the consideration of a question raised by the conclusions
of Steno.

Fossil Deposits Ascribed to the Flood. — After it began to
be reluctantly conceded that fossils might possibly be the
remains of former generations of animals and plants, there
followed a period characterized by the general belief that these
entombed forms had been deposited at the time of the
Mosaic deluge. This was the prevailing view in the eight-
eenth century. As observ^ation increased and the extent and
variety of fossil life became known, as well as the positions
in which fossils were found, it became more difficult to hold
this view with any appearance of reason. Large forms were
found on the tops of mountains, and also lighter forms were
found near the bottom. Miles upon miles of superimposed
rocks were discovered, all of them bearing quantities of
animal forms, and the interpretation that these had been
killed and distributed by a deluge became very strained. But

326 BIOLOGY AND ITS MAKERS

to the reasoners who gave free play to their fancies the facts
of observation afforded Httle difficulty. Some declared that
the entire surface of the earth had been reduced to the con-
dition of a pasty mass, and that the animals drowned by the
Deluge had been deposited within this pasty mass which,
on the receding of the waters, hardened into rocks.

The belief that fossil deposits were due to the Deluge
sensibly declined, however, near the close of the eighteenth
century, but was still warmly debated in the earlv part of the
nineteenth century. Fossil bones of large tropical animals
having been discovered about 1821, embedded in the stalag-
mite-covered floor of a cavern in Yorkshire, England, some
of the ingenious supporters of the flood- theory maintained
that caves were produced by gases proceeding from the bodies
of decaying animals of large size ; that they were like large
bubbles in the crust of the earth, and, furthermore, that bones
found in caverns were either those from the decayed carcasses
or others that had been deposited during the occurrence of
the Flood.

Even the utterances of Cuvier, in his theory of catastro-
phism to which we shall presently return, gave countenance
to the conclusion that the Deluge was of universal extent.
As late as 1823, William Buckland, reader in geology in
Oxford, and later canon (1825) of Christ Church, and dean
(1845) of Westminster, published his Reliquice DiluviancB, or
Observations on the Organic Remains Attesting the Action of
a Universal Deluge.

The theory that the Mosaic deluge had any part in the
deposit of organic fossils was finally surrendered through the
advance of knowledge, owing mainly to the labors of Lyell
and his followers.

The Comparison of Fossil and Living Animals. — The very
great interest connected with the reestablishment of the con-
clusion of Steno, that fossils were once alive, leads us to

SCIENCE OF FOSSIL REMAINS 327

speak more at length of the discoveries upon which Cuvier
passed his opinion. In the gypsum rocks about Paris the
workmen had been turning up to the Hght bones of enormous
size. While the workmen could recognize that they were
bones of some monsters, they were entirely at loss to imagine
to what kind of animals they had belonged, but the opinion
was frequently expressed that they were the bones of human
giants.

Cuvier, with his extensive preparation in comparative
anatomy, was the best fitted man perhaps in all the world
to pass judgment upon these particular bones. He went
to the quarries and, after observing the remains, he saw
very clearly that they were different from the bones of any
animals now existing. His great knowledge of comparative
anatomy was founded on a comprehensive study of the bony
system as well as the other structures of all classes of living
animals. He was familiar with the anatomy of elephants,
and when he examined the large bones brought to light in the
quarries of Montmartre, he saw that he was confronted with
the bones of elephant-like animals, but animals differing in
their anatomy from those at present living on the earth.

The great feature of Cuvier' s investigations was that he
instituted comparisons on a broad scale between fossil re-
mains and living animals. It was not merely that he fol-
lowed the method of investigation employed by Steno; he
went much further and reached a new conclusion of great
importance. Not only was the nature of fossil remains
determined, but by comparing their structure with that of
living animals the astounding inference was drawn that the
fossil remains examined belonged to forms that were truly
extinct. This discovery marks an epoch in the development
of the knowledge of extinct animals.

Cuvier the Founder of Vertebrate Palaeontology. — The
interesting discovery that the fossil relics in the Eocene rocks

328 BIOLOGY AND ITS MAKERS

about Paris embraced extinct species was announced to the
Institute by Cuvier in January, 1796; and thereafter he con-
tinued for a quarter of a century to devote much attention
to the systematic study of collections made in that district.
These observations were, however, shared with other labors
upon comparative anatomy and zoology, which indicates the
prodigious industry for which he was notable. In 181 2-
1813 he published a monumental work, profusely illustrated,
under the title Ossemens Fossiles. This standard publication
entitles him to recognition as the founder of vertebrate
palaeontology.

In examining the records of fossil life, Cuvier and others
saw that the evidence indicated a succession of animal popu-
lations that had become extinct, and also that myriads of new
forms of life appeared in the rocks of succeeding ages. Here
Cuvier, who believed that species were fixed and unalterable,
was confronted with a puzzling problem. In attempting to
account for the extinction of life, and what seemed to him
the creation of new forms, he could see no way out consistent
with his theoretical views except to assume that the earth
had periodically been the scene of great catastrophes, of
which the Mosaic deluge was the most recent, but possibly
not the last. He supposed that these cataclysms of nature
resulted in the extinction of all life, and that after each catas-
trophe the salubrious condition of the earth was restored,
and that it was re- peopled by anew creation of living beings.
This conception, known as the theory of catastrophism,
was an obstacle to the progress of science. It is to be re-
gretted that Cuvier was not able to accept the views of his
illustrious contemporary Lamarck, who believed that the
variations in fossil hfe, as well as those of living forms, were
owing to gradual transformations.

Lamarck Founds Invertebrate Palaeontology. — The credit
of founding the science of palaeontology does not belong

SCIENCE OF FOSSIL REMAINS 329

exclusively to Cuvier. Associated with his name as co-
founders are those of Lamarck and William Smith. Lamarck,
that quiet, forceful thinker who for so many years worked
by* the side of Cuvier, founded the science of invertebrate
palaeontology. The large bones with which Cuvier worked
were more easy to be recognized as unique or as belonging
to extinct animals than the shells which occurred in abundance
in the rocks about Paris. The latter were more difficult to
place in their true position because the number of forms
of Hfe in the sea is very extended and very diverse. Just as
Cuvier was a complete master of knowledge regarding verte-
brate organization, so Lamarck was equally a master of that
vast domain of animal forms which are of a lower grade
of organization — the invertebrates. From his study of the
collections of shells and other invertebrate forms from the
rocks, Lamarck created invertebrate palaeontology and this,
coupled with the work of Cuvier, formed the foundations of
the entire field.

Lamarck's study of the extinct invertebrates led him to
conclusions widely at variance with those of Cuvier. Instead
of thinking of a series of catastrophes, he saw that not all of
the forms of life belonging to one geological period became
extinct, but that some of them were continued into the suc-
ceeding period. He saw, therefore, that the succession of
life in the rocks bore testimony to a long series of gradual
changes upon the earth's surface, and did not in any way
indicate the occurrence of catastrophes. The changes, ac-
cording to the views of Lamarck, were all knit together into
a continuous process, and his conception of the origin of life
upon the earth grew and expanded until it culminated in the
elaboration of the first consistent theory of evolution.

These two men, Lamarck and Cuvier, form a contrast
as to the favors distributed by fortune: Cuvier, picturesque,
highly honored, the favorite of princes, advanced to the

330 BIOLOGY AND ITS MAKERS

highest places of recognition in the government, acclaimed
as the Jove of natural science; Lamarck, hard-working, ha-
rassed by poverty, insufficiently recognized, and, although
more gifted than his confrere, overlooked by the scientific
men of the time. The judgment of the relative position of
these two men in natural science is now being reversed, and
on the basis of intellectual supremacy Lamarck is coming
into general recognition as the better man of the two. In
the chapters dealing with organic evolution some events in
the life of this remarkable man will be given.

The Arrangement of Fossils in Strata. — The other name
associated with Lamarck and Cuvier is that of William Smith,
the English surveyor. Both Lamarck and Cuvier were men
of extended scientific training, but William Smith had a
moderate education as a surveyor. While the two former
were able to express scientific opinions upon the nature of
the fossil forms discovered, William Smith went at his task
as an observer with a clear and unprejudiced mind, an
observer who walked about over the fields, noticing the con-
ditions of rocks and of fossil forms embedded therein. He
noted that the organic remains were distributed in strata,
and that particular forms of fossil life characterized par-
ticular strata and occupied the same relative position to one
another. He found, for illustration, that certain particular
forms would be found underlying certain other forms in one
mass of rocks in a certain part of the country. Wherever
he traveled, and whatever rocks he examined, he found these
forms occupying the same relative positions, and thus he
came to the conclusion that the living forms within the rocks
constitute a stratified series, having definite and imvarying
arrangement with reference to one another.

In short, the work of these three men — Cuvier, Lamarck,
and William Smith — placed the new science of palaeontology
upon a secure basis at the beginning of the nineteenth century.

SCIENCE OF FOSSIL REMAINS 331

Summary. — The chief Steps up to this time in the growth
of the science of fossil remains may now be set forth in cate-
gories, though we must remember that the advances pro-
ceeded concurrently and were much intermingled, so that,
whatever arrangement we may adopt, it does not represent
a strict chronological order of events:

I. The determination of the nature of fossils. Owing to
the labors of Da Vinci, Steno, and Cuvier, the truth was estab-
lished that fossils are the remains of former generations of
animals and plants.

II. The comparison of organic fossils with living forms
that was instituted on a broad scale by Cuvier resulted in the
conclusion that some of the fossils belong to extinct races.
The behef of Cuvier that entire populations became extinct
simultaneously, led him to the theory of catastrophism. The
observations of Lamarck, that, while some species disappear,
others are continued and pass through transmutations, were
contrary to that theory.

III. The recognition that the stratified rocks in which
fossils are distributed are sedimentary deposits of gradual
formation. This observation and the following took the
groimd from under the theory that fossils had been deposited
during the Mosaic deluge.

IV. The discovery by William Smith that the arrangement
of fossils within rocks is always the same, and the relative
age of rocks may be determined by an examination of their
fossil contents.

Upon the basis of the foregoing, we come to the next
advance, viz.:

V. The application of this knowledge to the determination
of the history of the earth.

Fossil Remains as an Index to the Past History of the
Earth. — The most advanced and enlightened position that
had been taken in reference to the fossil series during the

33^

BIOLOGY AND ITS MAKERS

first third of the nineteenth century was that taken by
Lamarck, he being the first to read in the series the history
of Hfe upon the globe, weaving it into a connected story, and
estabhshing thereon a doctrine of organic evolution. It was
not until after 1859, however, that the truth of this conclusion
was generally admitted, and when it was accepted it was not
through the earlier publications of Lamarck, but through
the arguments of later observers, founded primarily upon
the hypothesis set forth by Darwin. There were several
gradations of scientific opinion in the period, short as it
was, between the time of Cuvier and of Darwin; and this
intermediate period was one of contention and warfare
between the theologians and the geologists. Cuvier had
championed the theory of a succession of catastrophes, and
since this hypothesis did not come into such marked conflict
with the prevailing theological opinion as did the views of
Lamarck, the theologians were ready to accept the notion of
Cuvier, and to point with considerable satisfaction to his
unique position as an authority.

Lyell. — In 1830 there was published an epoch-making
work in geology by Charles Lyell (Fig. 97), afterward
Sir Charles, one of the most brilliant geologists of all the
world. This British leader of scientific thought showed the
prevalence of a uniform law of development in reference to
the earth's surface. He pointed out the fact that had been
maintained by Hutton, that changes in the past were to be
interpreted in the light of what is occurring in the present.
By making a careful study of the work performed by the
waters in cutting down the continents and in transferring the
eroded material to other places, and distributing it in the form
of deltas ; by observing also the action of frost and wind and
wave; by noting, furthermore, the conditions under which
animals die and are subsequently covered up in the matrix
of detritus — by all this he showed evidences of a series of

SCIENCE OF FOSSIL REMAINS

333

slow, continuous changes that have occurred in the past and
have molded the earth's crust into its present condition.

He showed, further, that organic fossils are no exception
to this law of uniform change. He pointed to the evidences
that ages of time had been required for the formation of the
rocks bearing fossils; and that the regular succession of animal

Fig. 97. — Charles Lyell, 1797-1875.

forms indicates a continual process of development of animal
life ; and that the disappearance of some forms, that is, their
becoming extinct, was not owing to sudden changes, but to
gradual changes. When this view was accepted, it overthrew
the theory of catastrophism and replaced it by one designated
uniformatism, based on the prevalence of uniform natural
laws.

This new conception, with all of its logical inferences,

334 BIOLOGY AND ITS MAKERS

was scouted by those of theological bias, but it won its way
in the scientific world and became an important feature in
preparing for the reception of Darwin's great book upon the
descent of animal Hfe.

We step forward now to the year 1859, to consider the
effect upon the science of palaeontology of the publication of
Darwin's Origin of Species. Its influence was tremend-
ous. The geological theories that had provoked so much
controversy were concerned not merely with the disappear-
ance of organic forms, but also with the introduction of new
species. The Origin of Species made it clear that the only
rational point of view in reference to fossil life was that it
had been gradually developed, that it gave us a picture of
the conditions of life upon the globe in past ages, that the
succession of forms within the rocks represented in outline
the successive steps in the formation of different kinds of
animals and plants.

Owen. — Both before and after Darwin's hypothesis was
given to science, notable anatomists, a few of whom must be
mentioned, gave attention to fossil remains. Richard Owen
(1804-1892) had his interest in fossil hfe stimulated by a
visit to Cuvier in 1831, and for more than forty years there-
after he published studies on the structure of fossil animals.
His studies on the fossil remains of Australia and New
Zealand brought to light some interesting forms. The ex-
tinct giant bird of New Zealand (Fig. 98) was a spectacular
demonstration of the enormous size to which birds had
attained during the Eocene period. Owen's monograph
(1879) on the oldest known bird — the archaeopteryx — de-
scribed an interesting form uniting both bird-like and rep-
tilian characteristics.

Agassiz. — Louis Agassiz (1807-1873) (Fig. 99) also came
into close personal contact with Cuvier, and produced his
first great work partly under the stimulus of the latter. When

I

Fig. 98. — Professor Owen and the Extinct Fossil Bird (Dinornis)
of New Zealand.
Permission of D. Appleton & Co.

33^

BIOLOGY AND ITS MAKERS

Agassiz visited Paris, Cuvier placed his collections at Agassiz's
disposal, together with numerous drawings of fossil fishes.
The profusely illustrated monograph of Agassiz on the fossil
fishes (i 833-1 844) began to appear in 1833, the year after

Fig. 99. — Louis Agassiz, 1807-1873.

Cuvier' s death, and was carried on eleven years before it was
completed.

Agassiz, with his extensive knowledge of the developmen-
tal stages of animals, came to see a marked parallelism
between the stages in* development of the embryo and the
successive forms in the geological series. This remarkable
parallelism between the fossil forms of life and the stages

SCIENCE OF FOSSIL REMAINS 337

in the development of higher forms of recent animals is
very interesting and very significant, and helps materially
in elucidating the idea that the fossil series represent roughly
the successive stages through which animal forms have
passed in their upward course of development from the
simplest to the highest, through long ages of time. Curi-
ously enough, however, Agassiz failed to grasp the meaning
of the principle that he had worked out. After illustrating
so nicely the process of organic evolution, he remained !to the
end of his life an opponent of that theory. i

Huxley. — Thomas Henry Huxley (1825-1895) wals led
to study fossil life on an extended scale, and he shed light in
this province as in others upon which he touched. Wit)i crit-
ical analysis and impartial mind he applied the principles
of evolution to the study of fossil remains. His first conclu-
sion was that the evidence of evolution derived from palaeon-
tology was negative, but with the advances in discovery he
grew gradually to recognize that palaeontologists, in bringing
to light complete evolutionary series, had supplied some of
the strongest supporting evidence of organic evolution. By
many geologists fossils have been used as time-markers for
the determination of the age of various deposits; but, with
Huxley, the study of them was always biological. It is to
the latter point of view that palaeontology owes its great
importance and its great development. The statement of
Huxley, that the only difference between a fossil and a recent
animal is that one has been dead longer than the other,
represents the spirit in which the study is being carried
forward.

With the establishment of the doctrine of organic evolu-
tion palaeontology entered upon its modem phase of growth;
upon this basis there is being reared a worthy structure
through the efforts of the recent votaries to the science. It
is neither essential nor desirable that the present history of

33^

BIOLOGY AND ITS MAKERS

the subject should be followed here in detail. The collec-
tions of material upon which palaeontologists are working
have been enormously increased, and there is perhaps no
place where activity has been greater than in the United
States. The rocks of the Western States and Territories

Fig.

-E. D. Cope, 1840-1897.

embrace a very rich collection of fossil forms, and, through
the generosity of several wealthy men, exploring parties have
been provided for and immense collections have been brought
back to be preserved in the museums, especially of New
Haven, Conn., and in the American Museum of Natural His-
tory in New York City.

SCIENCE OF FOSSIL REMAINS 339

Leidy, Cope, and Marsh.— Among the early explorers of
the fossils of the West must be named Joseph Leidy, E. D.
Cope (Fig. 100), and O. C. Marsh. These gentlemen all
had access to rich material, and all of them made notable
contributions to the science of palaeontology. The work of

Fig. ioi. — O. C. Marsh, 1831-1899.

Cope (i 840-1 897) is very noteworthy. He was a compar-
ative anatomist equal to Cuvier in the extent of his knowl-
edge, and of larger philosophical views. His extended publi-
cations under the direction of the United States Government
have very greatly extended the knowledge of fossil vertebrate
life in America.

340 BIOLOGY AND ITS MAKERS

O. C. Marsh (Fig. loi) is noteworthy for similar explora-
tions; his discovery of toothed birds in the Western rocks
and his collection of fossil horses, until recently the most com-
plete one in existence, are all very well known. Throughout
his long life he contributed from his own private fortune, and
intellectually through his indefatigable labors, to the progress
of palaeontology.

Zittel. — The name most widely known in palaeontology
is that of the late Karl von Zittel (1839- 1904), who devoted
all his working hfe to the advancement of the science of fos-
sils. : In his great work, Handhuch der Palaeontologie (1876-
1893), he brought under one view the entire range of fossils
from the protozoa up to the mammals. Osbom says: ''It
is probably not an exaggeration to say that he did more for
the promotion and diffusion of palaeontology than any other
single man who lived during the nineteenth century. While
not gifted with genius, he possessed extraordinary judg-
ment, critical capacity, and untiring industry." His portrait
(Fig.! iv02) shows a face "full of keen intelligence and enthu-
siasn^."

Zjittel's influence was exerted not only through his writ-
ings,* but also through his lectures and the stimulus imparted
to the large number of young men who were attracted to
Munich to study under his direction. These disciples are
now j distributed in various universities in Europe and the
United States, and are there carrying forward the work begun
by Zittel. The great collection of fossils which he left at
Munich contains illustrations of the whole story of the evolu-
tion of life through geological ages.

Recent Developments. — The greatest advance now being
made in the study of fossil vertebrate life consists in establish-
ing the lineage of families, orders, and classes. Investigators
have been especially fortunate in working out the direct line
of descent of a number of living mammals. Fossils have

SCIENCE OF FOSSIL REMAINS

341

been collected which supply a panoramic view of the line of
descent of horses, of camels, of rhinoceroses, and of other
animals. The most fruitful worker in this field at the present
time is perhaps Henry F. Osborn, of the American Museum

i^^^^^^^^^^^l

IL5

K
m

iF

■1'.. '.■■■.K;':-

5*

1

Fig. 102. — Karl von Zittel, 1839-1904.

of Natural History, New York City. His profound and
important investigations in the ancestry of animal life are
now nearing the time of their publication in elaborated
form.

342 BIOLOGY AND ITS MAKERS

Palaeontology, by treating fossil life and recent life in the
same category, has come to be one of the important lines of
investigation in biology. It is, of course, especially rich in
giving us a knowledge of the hard parts of animals, but by
ingenious methods we can arrive at an idea of some of the
soft parts that have completely disappeared. Molds of the
interior of the cranium can be made, and thus one may form
a notion of the relative size and development of the brain
in different vertebrated animals. This method of making
molds and studying them has shown that one characteristic
of the geological time of the tertiary period was a marked
development in regard to the brain size of the different
animals. There was apparently, just prior to the quaternary
epoch, a need on the part of animals to have an increased
brain-growth; and one can not doubt that this feature which
is demonstrated by fossil life had a great influence in the
development of higher animal forms.

The methods of collecting fossils in the field have been
greatly developed. By means of spreading mucilage and
tissue paper over delicate bones that crumble on exposure
to the air, and of wrapping fossils in plaster casts for trans-
portation, it has been made possible to uncover and preserve
many structures which with a rougher method of handling
would have been lost to science.

Fossil Man. — One extremely interesting section of palae-
ontology deals with the fossil remains of the supposed
ancestors of the present human race. Geological evidence
establishes the great antiquity of man, but up to the present
time little systematic exploration has been carried on with
a view to discover all possible traces of fossil man. From
time to time since 1840 there have been discovered in caverns
and river- gravels bones which, taken together, constitute an
interesting series. The parts of the skull are of especial
importance in this kind of study, and there now exists in

SCIENCE OF FOSSIL REMAINS 343

different collections a series containing the Neanderthal
skull, the skulls of Spy and Engis, and the Java skull de-
scribed in 1894 by Dubois. There have also been found
recently (November, 1906) in deposits near Lincohi, Neb.,
some fossil human remains that occupy an intermediate
position between the Neanderthal skull and the skulls of the
lower representatives of living races of mankind. We shall
have occasion to revert to this question in considering the
evidences of organic evolution. (See page 364.)

The name palaeontology was brought into use about 1830.
The science affords, in some particulars, the most interesting
field for biological research, and the feature of the recon-
struction of ancient life and the determination of the lineage
of living forms has taken a strong hold on the popular imag-
ination. According to O shorn, the most important palaeon-
tological event of recent times was the discovery, in 1900, of
fossil beds of mammals in the Faylim lake-province of Egypt,
about forty-seven miles south of Cairo. Here are embedded
fossil forms, some of which have been already described in a
volume by Charles W. Andrews, which Osbom says ''marks
a turning-point in the history of mammalia of the world."
It is now estabHshed that "Africa was a very important center
in the evolution of mammalian life." It is expected that the
lineage of several orders of mammalia will be cleared up
through the further study of fossils from this district.

PART II

THE DOCTRINE OF ORGANIC
EVOLUTION

CHAPTER XVI

WHAT EVOLUTION IS: THE EVIDENCE UPON
WHICH IT RESTS, ETC.

The preceding pages have been devoted mainly to an
account of the shaping of ideas in reference to the architec-
ture, the physiolog}^, and the development of animal life.

We come now to consider a central theme into which all
these ideas have been merged in a unified system; viz., the
process by which the diverse forms of animals and plants
have been produced.

Crude speculations regarding the derivation of living
forms are very ancient, and we may say that the doctrine of
organic evolution was foreshadowed in Greek thought. The
serious discussion of the question, however, was reserved
for the nineteenth century. The earlier naturalists accepted
animated nature as they found it, and for a long time were
engaged in becoming acquainted merely, with the different
kinds of animals and plants, in working out their anatomy
and development; but after some progress had been made
in this direction there came swinging into their horizon
deeper questions, such as that of the derivation of living
forms. The idea that the higher forms of life are de-
rived from simpler ones by a process of gradual evolution
received general acceptance, as we have said before, only
in the last part of the nineteenth century, after the work of
Charles Darwin; but we shall presently see how the theory
of organic development was thought out in completeness by

347

348 BIOLOGY AND ITS MAKERS

Lamarck in the last years of the eighteenth century, and was
further molded by others before Darwin touched it.

Vagueness Regarding Evolution. — Although ''evolution"
is to-day a word in constant use, there is still great vagueness
in the minds of most people as to what it stands for; and,
what is more, there is very little general information dissem-
inated regarding the evidence by which it is supported, and re-
garding the present status of the doctrine in the scientific world.

In its broad sense, evolution has come to mean the devel-
opment of all nature from the past. We may, if we wish,
think of the long train of events in the formation of the world,
and in supplying it with life as a story inscribed upon a scroll
that is being gradually unrolled. Everything which has
come to pass is on that part so far exposed, and everything
in the future is still covered, but will appear in due course
of time; thus the designation of evolution as ''the unrolling
of the scroll of the universe" becomes picturesquely sug-
gestive. In its wide meaning, it includes the formation of
the stars, solar systems, the elements of the inorganic world,
as well as all living nature — this is general evolution; but
the word as commonly employed is limited to organic evolu-
tion, or the formation of life upon our planet. It will be
used hereafter in this restricted sense.

The vagueness regarding the theory of organic evolution
arises chiefly from not understanding the points at issue.
One of the commonest mistakes is to confuse Darwinism
with organic evolution. It is known, for illustration, that con-
troversies are current among scientific workers regarding
Darwinism and certain phases of evolution, and from this
circumstance it is assumed that the doctrine of organic
evolution as a whole is losing ground. The discussions of De
Vries and others — all believers in organic evolution — at the
Scientific Congress in St. Louis in 1904, led to the statement
in the public press that the scientific world was haggling

ORGANIC EVOLUTION 349

over the evolution-theory, and that it was beginning to sur-
render it. Such statements are misleading and tend to per-
petuate the confusion regarding the present status of the
evolution theory. Never before was the doctrine of organic
evolution so thoroughly entrenched in the mind of the
scientific world.

The theory of organic evolution relates to the history of
animal and plant hfe, while Darwin's theory of natural selec-
tion is only one of the various attempts to point out the
causes for that history's being what it is. An attack upon
Darwinism is not, in itself, an attack upon the general the-
ory, but upon the adequacy of his explanation of the way
in which nature has brought about the diversity of animal
and plant life. Natural selection is the particular factor
which Darwin has emphasized, and the discussion of the
part played by other factors tends only to extend the knowl-
edge of the evolutionary process, without detracting from it
as a general theory.

While the controversies among scientific men relate for
the most part to the influences that have been operative in
bringing about organic evolution, nevertheless there are a few
in the scientific camp who repudiate the doctrine. Fleisch-
mann, of Erlangen, is perhaps the most conspicuous of those
who are directing criticism against the general doctrine,
maintaining that it is untenable. Working biologists will be
the first to admit that it is not demonstrated by indubitable
evidence, but the weight of evidence is so compelling that
scientific men as a body regard the doctrine of organic evolu-
tion as merely expressing a fact of nature, and we can not
in truth speak of any considerable opposition to it. Since
Fleischmann speaks as an anatomist, his suppression of
anatomical facts with which he is acquainted and his form of
special pleading have impressed the biological world as lack-
ing in sincerity.

3SO BIOLOGY AND ITS MAKERS

This is not the place, however, to deal with the technical
aspects of the discussion of the factors of organic evolution;
it is rather our purpose here to give a descriptive account of
the theory and its various explanations. First we should
aim to arrive at a clear idea of what the doctrine of evolution
is, and the basis upon which it rests; then of the factors which
have been emphasized in attempted explanations of it; and,
finally, of the rise of evolutionary thought, especially in the
nineteenth century. The bringing forward of these points
will be the aim of the following pages.

Nature of the Question. — It is essential at the outset to
perceive the nature of the question involved in the theories
of organic evolution. It is not a metaphysical question, ca-
pable of solution by reflection and reasoning with symbols;
the data for it must rest upon observation of what has taken
place in the past in so far as the records are accessible. It
is not a theological question, as so many have been disposed
to argue, depending upon theological methods of interpreta-
tion. It is not a question of creation through divine agencies,
or of non-creation, but a question of method of creation.

Evolution as used in biology is merely a history of the
steps by which animals and plants came to be what they are.
It is, therefore, a historical question, and must be investigated
by historical methods. Fragments of the story of creation
are found in the strata of the earth's crust and in the stages
of embryonic development. These clues must be brought
together; and the reconstruction of the story is mainly a
matter of getting at the records. Drummond says that evo-
lution is "the story of creation as told by those who know
it best."

The Historical Method. — The historical method as ap-
plied to searchhig out the early history of mankind finds a
parallel in the investigations into the question of organic
evolution. In the buried cities of Palestine explorers have

ORGANIC EVOLUTION 35^

uncovered traces of ancient races and have in a measure
reconstructed their history from fragments, such as coins,
various objects of art and of household use, together with
inscriptions on tom.bs and columns and on those curious little
bricks which were used for public records and correspond-
ence. One city having been uncovered, it is found by lifting
the floors of temples and other buildings, and the pavement
of public squares, that this city, although very ancient, is
built upon the ruins of a more ancient one, which in turn
covers the ruins of one still older. In this way, as many as
seven successive cities have been found, built one on top of
the other, and new and unexpected facts regarding ancient
civilization have been brought to light. We must admit that
this gives us an imperfect history, with many gaps; but it is
one that commands our confidence, as being based on facts
of observation, and not on speculation.

In like manner the knowledge of the past history of animal
life is the result of explorations by trained scholars into the
records of the past. We have remains of ancient life in the
rocks, and also traces of past conditions in the developing
stages of animals. These are all more ancient than the
inscriptions left by the hand of man upon his tombs, his
temples, and his columns, but nevertheless full of meaning
if we can only understand them. This historical method of
investigation applied to the organic world has brought new
and unexpected views regarding the antiquity of life.

The Diversity of Living Forms. — Sooner or later the
question of the derivation of the animals and plants is
bound to come to the mind of the observer of nature. There
exist at present more than a million different kinds of
animals. The waters, the earth, the air teem with life.
The fishes of the sea are almost innumerable, and in a sin-
gle order of the insect- world, the beetles, more than 50,000
species are known and described. In addition to living

352 BIOLOGY AND ITS MAKERS

animals, there is entombed in the rocks a great multitude
of fossil forms which lived centuries ago, and many of which
have become entirely extinct. How shall this great diversity
of life be accounted for? Has the great variety of forms
existed unchanged from the days of their creation to the
present ? Or have they, perchance, undergone modifications
so that one original form, or at least a few original types,
may have through transformations merged into different
kinds ? This is not merely an idle question, insoluble from
the very nature of the case; for the present races of animals
have a lineage reaching far into the past, and the question
of fixity of form as against alteration of type is a historical
question, to be answered by getting evidence as to their line
of descent.

Are Species Fixed in Nature? — The aspect of the matter
which presses first upon our attention is this: Are the species
(or different kinds of animals and plants) fixed, and, within
narrow limits, permanent, as Linnaeus supposed? Have
they preserved their identity through all time, or have they
undergone changes ? This is the heart of the question of
organic evolution. If observation shows species to be con-
stant at the present time, and also to have been continuous
so far as we can trace their parentage, we must conclude that
they have not been formed by evolution; but if we find
evidence of their transmutation into other species, then there
has been evolution.

It is well estabhshed that there are wide ranges of varia-
tion among animals and plants, both in a wild state and under
domestication. Great changes in flowers and vegetables are
brought about through cultivation, while breeders produce
different kinds of pigeons, fowls, and stock. We know,
therefore, that living beings may change through modification
of the circumstances and conditions that affect their lives.
But general observations extending over a few decades are

ORGANIC EVOLUTION 353

not sufficient. We must, if possible, bring the history of
past ages to bear upon the matter, and determine whether or
not there had been, with the lapse of time, any considerable
alteration in living forms.

Evolutionary Series. — Fortunately, there are preserved
in the rocks the petrified remains of animals, showing their
history for many thousands of years, and we may use them
to test the question. It is plain that rocks of a lower level
were deposited before those that cover them, and we may
safely assume that the fossils have been preserved in their
proper chronological order. Now, we have in Slavonia some
fresh-water lakes that have been drying up from the tertiary
period. Throughout the ages, these waters were inhabited
by snails, and naturally the more ancient ones were the par-
ents of the later broods. As the animals died their shells
sank to the bottom and were covered by mud and debris,
and held there like currants in a pudding. In the course of
ages, by successive accumulations, these layers thickened
and were changed into rock, and by this means shells have
been preserved in their proper order of birth and life, the most
ancient at the bottom and the newest at the top. We can
sink a shaft or dig a trench, and collect the shells and arrange
them in proper order.

Although the shells in the upper strata are descended from
those near the bottom, they are very different in appearance.
No one would hesitate to name them different species; in
fact, when collections were first made, naturalists classified
these shells into six or eight different species. If, however, a
collection embracing shells from all levels is arranged in a
long row in proper order, a different light is thrown on the
matter; while those at the ends are unlike, yet if we begin
at one end and pass to the other we observe that the shells
all grade into one another by such slight changes that there
is no line showing where one kind leaves off and another

354

BIOLOGY AND ITS MAKERS

begins. Thus their history for thousands of years bears
testimony to the fact that the species have not remained
constant, but have changed into other species.

Fig. 103 will give an idea of the varieties and gradations.
It represents shells of a genus, Paludina, which is still abun-
dant in most of the fresh waters of our globe.

Fig. 103. — Transmutations of Paludina. (After Neumayer.)

A similar series of shells has been brought to light in
Wiirttemberg in which the variations pass through wider
limits, so that not only different species may be observed,
but different genera connected by almost insensible grada-
tions. These transformations are found in a little flattened

ORGANIC EVOLUTION

355

pond-shell similar to the planorbis, which is so common at
the present time.

Fig. 104 shows some of these transformations, the finer

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gradations being omitted. The shells from these two sources
bear directly upon the question of whether or not species have
held rigidly to their original form.

356 BIOLOGY AND ITS MAKERS

After this kind of revelation in reference to lower animals,
we turn with awakened interest to the fossil bones of the
higher animals.

Evolution of the Horse. — When we take into account the
way in which fossils have been produced we see clearly that
it is the hard parts, such as the shells and the bones, that will
be preserved, while the soft parts of animals will disappear.
Is it not possible that we may find the fossil bones of higher
animals arranged in chronological order and in sufficient
number to supplement the testimony of the shells? There
has been preserved in the rocks of our Western States a very
complete history of the evolution of the horse family, written,
as it were, on tablets of stone, and extending over a period
of more than two million years, as the geologists estimate
time. Geologists can, of course, measure the thickness of
rocks and form some estimate of the rate at which they were
deposited by observing the character of the material and com-
paring the formation with similar water deposits of the
present time. Near the surface, in the deposits of the
quarternary period, are found remains of the immediate
ancestors of the horse, which are recognized as belonging
to the same genus, Equus, but to a different species; thence,
back to the lowest beds of the tertiary period we come
upon the successive ancestral forms, embracing several dis-
tinct genera and exhibiting an interesting series of trans-
formations.

If in this way we go into the past a half-million years, we
find the ancestors of the horse reduced in size and with three
toes each on the fore and hind feet. The living horse now
has only a single toe on each foot, but it has small splint-like
bones that represent the rudiments of two more. If we go
back a million years, we find three toes and the rudiments
of a fourth; and going back two million years, we find four
fully developed toes, and bones in the feet to support them.

ORGANIC EVOLUTION 357

It is believed that in still older rocks a five-toed form will be
discovered, which was the parent of the four- toed form.

In the collections at Yale College there are preserved
upward of thirty steps or stages in the history of the horse
family, showing that it arose by evolution or gradual change
from a four- or five- toed ancestor of about the size of a fox,
and that it passed through many changes, besides increase
in size, in the two million years in which we can get facts
as to its history.

Remarkable as is this feature of the Marsh collection at
New Haven, it is now surpassed by that in the Museum of
Natural History in New York City. Here, through the
munificent gifts of the late W. C. Whitney, there has been
accumulated the most complete and extensive collection of
fossil horses in the world. This embraced, in 1904, some
portions of 710 fossil horses, 146 having been derived from
explorations under the Whitney fund. The extraordinary
character of the collection is shown from the fact that it
contains five complete skeletons of fossil horses — more than
existed at that time in all other museums of the world.

The specimens in this remarkable collection show phases in
the parallel development of three or four distinct races of horse-
like animals, and this opens a fine problem in comparative
anatomy; viz., to separate those in the direct line of ancestry
of our modem horse from all the others. This has been
accomplished by O shorn, and through his critical analysis
we have become aware of the fact that the races of fossil
horses had not been distinguished in any earlier studies.
As a result of these studies, a new ancestry of the horse,
differing in details from that given by Huxley and Marsh, is
forthcoming.

Fig. 105 shows the bones of the foreleg of the modem
horse, and Fig. 106 some of the modifications through which
it has passed. Fig. 107 shows a reconstruction of the ances-

358

BIOLOGY AND ITS MAKERS

tor of the horse made by Charles R. Knight, the animal
painter, under the direction of Professor O shorn.

While the limbs were undergoing the changes indicated,
other parts of the organism were also being transformed

Fig. 105. — Bones of the Foreleg and Hindleg of a Horse.

and adapted to the changing conditions of its life. The
evolution of the grinding teeth of the horse is fully exhibited
in the fossil remains. All the facts bear testimony that
the horse was not originally created as known to-day, but
that his ancestors existed in different forms, and in evolution
have transcended several genera and a considerable num-
ber of species. The highly specialized limb of the horse
adapted for speed was the product of a long series of changes,

ORGANIC EVOLUTION

359

of which the record is fairly well preserved. Moreover, the
records show that the atavus of the horse began in North
America, and that by migration the primitive horses spread
from this continent to Europe, Asia, and Africa.

So far we have treated the question of fixity of species as
a historical one, and have gone searching for clues of past

Fig. io6. — Bones of the Foreleg and Molar Teeth of Fossil Ancestors
of the Horse. European Forms. (After Kayser.)

conditions just as an archaeologist explores the past in buried
cities. The facts we have encountered, taken in connection
with a multitude of others pointing in the same direction,
begin to answer the initial question. Were the immense num-
bers of living forms created just as we find them, or were
they evolved by a process of transformation ?

36o BIOLOGY AND ITS MAKERS

The geological record of other families of mammals has
also been made out, but none so completely as that of the
horse family. The records show that the camels were native
in North America, and that they spread by migration from
the land of their birth to Asia and Africa, probably crossing
by means of land-connections which have long since become
submerged.

The geological record, considered as a whole, shows that
the earlier formed animals were representatives of the lower
groups, and that when vertebrate animals were formed, for
a very long time only fishes were living, then amphibians,,
reptiles, birds, and finally, after immense reaches of time,,
mammals began to appear.

Connecting Forms. — Interesting connecting forms be-
tween large groups sometimes are found, or, if not connecting
forms, generalized ones embracing the structural character-
istics of two separate groups. Such a form is the archa^op-
teryx (Fig. io8), a primitive bird with reptilian anatomy,,
with teeth in its jaws, and a long, lizard-like tail covered with
feathers, which seems to show connection between birds and
reptiles. The wing also shows the supernumerary fingers,,
which have been suppressed in modem birds. Another sug-
gestive type of this kind is the flying reptile or pterodactyl,.
of which a considerable number have been discovered.
Illustrations indicating that animals have had a common line
of descent might be greatly multiphed.

The Embryological Record and its Connection with Evo-
lution.— The most interesting, as well as the most compre-
hensive clues bearing on the evolution of animal life are
found in the various stages through which animals pass on
their way from the egg to the fully formed animal. All
animals above the protozoa begin their lives as single cells,,
and between that rudimentary condition and the adult stage
every gradation of structure is exhibited. As animals de-

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velop they become successively more and more complex,
and in their shifting history many rudimentary organs arise

Fig. 108. — Fossil Remains of a Primitive Bird (Archeopteryx).
From the specimen in the Beriin Museum. (After Kayser.)

and disappear. For illustration, in the young chick, devel-
oping within the hen's egg, there appear, after three or four

ORGANIC EVOLUTION

Z^3

days of incubation, gill-slits, or openings into the throat,
like the gill-openings of lower fishes. These organs belong
primarily to water life, and are not of direct use to the chick.

Fig. 109. — The Gill-clefts of a Shark (upper fig.) Compared with
Those of the Embryonic Chick (to the left) and Rabbit.

The heart and the blood-vessels at this stage are also of the
fish-like type, but this condition does noi last long; the gill-
slits, or gill-clefts, fade away within a few days, and the

364

BIOLOGY AND ITS MAKERS

arteries of the head and the neck undergo great changes long
before the chick is hatched. Similar gill-clefts and similar
arrangements of blood-vessels appear also very early in the
development of the young rabbit, and in the development
of all higher life. Except for the theory of descent, such
things would remain a lasting enigma. The universal pres-
ence of gill-clefts is not to be looked on as a haphazard

Fig.

-The Jaws of an Embryonic Whale, Showing Rudimentary
Teeth.

occurrence. They must have some meaning, and the best
suggestion so far offered is that they are survivals inherited
from remote ancestors. The higher animals have sprung
from simpler ones, and the gill- slits, along with other rudi-
mentary organs, have been retained in their history. It is
not necessary to assume that they are inherited from adult
ancestors; they are, more likely, embryonic structures still
retained in the developmental history of higher animals.

ORGANIC EVOLUTION 365

Such traces are like inscriptions on ancient columns — they
are clues to former conditions, and, occurring in the animal
series, they weigh heavily on the side of evolution.

An idea of the appearance of gill-clefts may be obtained
from Fig. 109 showing the gill- clefts in a shark and those In
the embryo of a chick and a rabbit.

Of a similar nature are the rudimentary teeth in the jaws
of the embryo of the whalebone whale (Fig. no). The
adults have no teeth, these appearing only as transitory rudi-
ments in the embryo. It is to be assumed that the teeth are
inheritances, and that the toothless baleen whale is derived
from toothed ancestors.

If we now turn to comparative anatomy, to classification,
and to the geographical distribution of animals, we find that
it is necessary to assume the doctrine of descent in order
to explain the observed facts; the evidence for evolution,
indeed, becomes cumulative. But it is not necessary, nor
will space permit, to give extended illustrations from these
various departments of biological researches.

The Human Body. — Although the broad doctrine of evo-
lution rests largely upon the observation of animals and plants,
there is naturally unusual interest as to its teaching in ref-
erence to the development of the human body. That the
human body belongs to the animal series has long been
admitted, and that it has arisen through a long series of
changes is shown from a study of its structure and develop-
ment. It retains marks of the scaffolding in its building.
The human body has the same devious course of embryonic
development as that of other mammals. In the course of
its formation gill-clefts make their appearance; the circula-
tion is successively that of a single-, a double-, and a four-
chambered heart, with blood-vessels for the gill-clefts. Time
and energy are consumed in building up rudimentary struc-
tures which are evanescent and whose presence can be best

366 BIOLOGY AND ITS MAKERS

explained on the assumption that they are, as in other animals,
hereditary survivals.

Wiedersheim has pointed out more than one hundred
and eighty rudimentary or vestigial structures belonging to
the human body, which indicate an evolutionary relation-
ship with lower vertebrates. It would require a considerable
treatise to present the discoveries in reference to man's
organization, as Wiedersheim has done in his Structure of
Man. As passing illustrations of the nature of some of these
suggestive things bearing on the question of man's origin
may be mentioned : the strange grasping power of the newly
bom human infant, retained for a short time, and enabling
the babe to sustain its weight; the presence of a tail and
rudimentary tail muscles; of rudimientary ear muscles; of
gill-clefts, etc.

Antiquity of Man. — ^The story of prehistoric man is im-
perfectly known, although sporadic explorations have already
accumulated an interesting series of evidences bearing on
the subject, such as primitive stone implements of human
manufacture, crude sketches of extinct animals by prehistoric
artists, and fossil remains of primitive man showing grada-
tions in the shape and capacity of skulls. All these cor-
related sources afford most convincing proofs of man's
great antiquity. He has left traces of his occupancy of
the Earth, especially in central and southwestern Europe
and in England, long before the davm of the historical
period.

The prehistoric stone implements are found associated
with the bones of extinct animals in caves, and imbedded in
the strata of soil and gravel that have remained undisturbed
for many centuries. They are of three grades: neoliths, the
more recent ones, carefully shaped with skill and artistic
feeling; palaeoliths, very ancient, rude, but evidently shaped
by design; and eoliths, rough stone chips bearing evidence of

ORGANIC EVOLUTION 367

use and indicating the existence of man of less developed
skill. These latter implements carry the traces of a tool-
making creature back into the Tertiary period.

Besides the stone implements there are many sketches of
extinct animals by prehistoric artists, scratched on bone,
ivory, slate, and on the walls of caves. The inference to be
drawn from these sketches is that man was alive in central
and southwestern Europe when the hairy mammoth and
the reindeer occupied the same territory. The crude sketches
of palaeolithic man, just referred to, merge by gradations
into the more carefully drawn, and sometimes colored
sketches, of neoHthic man. Those of the Cave of Altamira,
in Spain, are very notable products of neoHthic artists. They
have been described and many of them reproduced in colored
illustrations in Cartailhac and Breuil's La Caverne d' Altamira,
(1906) . They represent the golden period of prehistoric art.

The range of discovery of fossil human relics gives evidence
of a wide geographical distribution of primitive races during
the palaeohthic time. Variations in the degree of skill in
the manufacture of stone implements, as well as in other
particulars, have brought to archaeologists the recognition of
different culture periods, which are well exhibited in different
parts of France and Central Europe. Not less than six cul-
ture periods of palaeolithic man are recognized, indicating
that the prehistoric period of human development was far
longer than the entire historic period.

It is, however, to fossil remains of primitive man that we
must look for evidences of structural changes that have
taken place in the human frame.

Of all the bony parts the skull is the most interesting for
comparison, since its size and configuration indicate in a
general way the degree of development of the brain, and, as
a consequence, the relative grade of intelligence.

One of the most famous documents of ancestral history is

368 BIOLOGY AND ITS MAKERS

the well-known Neanderthal skull, discovered in a cave near
Diisseldorf in the valley of the Neander, in 1856 and first
described in 1857. It is now exhibited with other parts of
the skeleton in the provincial museum at Bonn on the Rhine.
The inferences drawn from the anatomical study of this
very ancient skull, with its low receding forehead, showing
small development in the region of the higher mental facul-
ties, created a sensation, and great opposition was developed
to allowing the discovery to rank as an evidence of primitive
man. But its importance has become enhanced by the dis-
covery of a long series of similar skulls. In 1886 came the
discovery in the Cave of Spy, Belgium, of two skeletons with
the same structural features as those of the Neanderthal
remains, and since that time the discoveries of numerous
similar relics have established the existence of a Neanderthal
race Hving in the middle of the palaeolithic period. The more
notable members of the Neanderthaloid series embrace: the
human remains of Krapina, in Croatia, found in 1899- 1904,
and consisting of parts of the skeletons of ten persons from
infancy to old age; the skeletal remains of La Chapelle aux-
Saints and of Le Moustier. In August, 1908, there was dis-
covered in Southwestern France (Correze), by well directed
efforts of French archaeologists, a very interesting skeleton
of the Neanderthal type, and now known as the man of La
Chapelle aux-Saints. This is the skeleton of an old man with
an almost complete skull, and a lower jaw lacking some of the
teeth. Since the comprehensive analysis of these remains,
published by Boule in 19 13, this is the most thoroughly
known skeleton of the Neanderthal race and may be taken
as a type. Besides the structural features of the bony parts,
it is interesting to note that the casts of the interior of the
cranium show the surface features of the brain. As com-
pared with the brain of modern man, it is small in the region
of the frontal lobes and shows a greater simplicity in the

ORGANIC EVOLUTION 369

pattern of the convolutions. A somewhat more primitive
type was discovered a few months earlier (March, 1908) at
the famous station of Le Moustier (Dordogne). It is the
skull of a young person and valuable for comparison. These
human relics of the Neanderthal age have been named scien-
tifically Homo neanderthalensis (or primigenius) , Homo mou-
stierensis, etc., thus including them in the same genus with
Homo sapiens of Linnaeus.

These aboriginal people represent one link of the chain of
human ancestry, and they were followed by a more developed
type of primitive man before the dawn of history, and the
emergence of the modern type.

A much more interesting circumstance is that the Neander-
thal people were also preceded by more primitive pre-humans.
There are known at present three examples of remains that
are distinctly pre-Neanderthaloid. The first to be discov-
ered, and also the most primitive pre-human species known,
is represented by portions of the skull and of the leg bones,
found in Central Java by the Dutch surgeon, Dubois, during
the years 1891 and 1892, and made known in 1894. These
remains were found in tertiary deposits and were baptized
under the name of Pithecanthropus erectus. The capacity of
the skull, 930 cubic centimeters, precludes the conclusion
that it belongs to the anthropoid series; the largest cranial
capacity of apes, living or fossil, not exceeding 600 cubic
centimetres.

The second pre-Neanderthaloid is the perfect lower jaw
with all the teeth, discovered in 1907 in the sands of Mauer,
near Heidelberg. These deposits belong to the lower quarter-
nary, and since the discovery of the Heidelberg jaw it is
claimed that Eoliths have been discovered in the same layer.
The jaw, while distinctly human as to characteristics of the
teeth, is very primitive. The creature to which it belonged
has been designated Homo Heidelbergensis.

370 BIOLOGY AND ITS MAKERS

The most recent discovery of pre-human remains comes
from England. At Piltdown Common, in Sussex, in 191 2,
there was unearthed a skull, with parts of the lower jaw and
teeth, that fits into the series of the pre-Neanderthaloid.
It has been suggestively named the dawn man {Eoanthropus
Dawsonii). The controversies of Dr. Smith-Woodward and
Professor Keith over details of the reconstruction of missing
parts, and the estimated capacity of the skull, were given
wide publicity through the periodical Nature. They are
technical and do not materially affect the question of the
great antiquity of this skull and its relative position in the
series.

Above the Neanderthal race come the numerous fossil
remains of Neolithic man, merging by structural gradations
into those of recent type. The skeleton of Men tonne, that
of Combe Chapelle (1909), of Galley Hill (1895), the skull of
Engis, the cro-mangon race, and other representatives, are
the forms that connect palaeoHthic with recent man.

Putting these discoveries together we have an interesting
series of gradations of skulls, leading one into the other, and
covering a range of cranial capacity from 930 cu. cm., that
of the Java man, to 1480-1555 cu. cm., that of the average
adult white European. The Neanderthal skulls occupy an
intermediate position with a cranial capacity of approxi-
mately 1400 cu. cm.

Figure in shows in outline profile reconstructions of some
of the fossil types as compared with the short-headed type of
Europe.

In tracing backwards from recent man, it is not to be as-
sumed that the ancestral line breaks off abruptly. Even the
Java man had antecedents, and it is natural to assume his
derivation from an extinct primate of the earlier tertiary de-
posits. Positive evidences are lacking, but the known pres-
ence of anthropomorphous primates in the Miocene of France

ORGANIC EVOLUTION j^yi

offers a possible suggestion. Osborn (19 lo) has pointed out
that ''The only known Miocene and Pliocene primate which
might be considered an 'Eolith' maker is Dryopithecus; all
others belong to existing phyla of monkeys, baboons, and
apes." Palaeontological discoveries have supplied the line
of genealogy of several families of mammals, and if, on this
basis, we assume that man and the anthropoid apes had a
generalized ancestor, it is nevertheless clear that the human
and the simian Knes have had an independent development
for many centuries. There has been no crossing of the lines
since tertiary times.

Fig. I II. — Profile Reconstructions of the Skulls of Living and
Fossil Men: i. Brachycephalic European; 2. The more ancient
of the Nebraska skulls; 3. The Neanderthal man; 4. One of the
Spy skulls; 5. Skull of the Java man. (Altered from Schwalbe
and Osborn.)

The derivation of man from an extinct tertiary Primate
seems already to be well authenticated. Furthermore, the
fossil records give evidence of the conditions under which the
development of the higher races of animals began. By mak-
ing casts of the interior of the fossil skulls of tertiary mam-

372 BIOLOGY AND ITS MAKERS

mals, it has been determined that there was in that geological
period a marked increase in the size of the brain. This cir-
cumstance was of the greatest importance both for progress
and for perpetuity of certain kinds of animals. Those in
particular whose increased intelligence enabled them to cope
more successfully with the conditions of their existence, and
to turn natural forces to their advantage, were continued and
improved. In pre-humans the increase in brain surface led
to the power of storing up mental impressions and experi-
ences, and, finally, brought about a condition of educability
which formed the starting point for marked improvement.

Mental Evolution. — Already the horizon is being wid-
ened, and new problems in human evolution have been opened.
The evidences in reference to the evolution of the human
body are so compelling as to be already generally accepted,
and we have now the question of evolution of mentality to
deal with. The progressive intelligence of animals is shown
to depend upon the structure of the brain and the nervous
syste"ta, and there exists such a finely graded series in this
respect that there is strong evidence of the derivation of hu-
man faculties from brute faculties.

Sweep of the Doctrine of Evolution. — The great sweep
of the doctrine of evolution makes it ''one of the greatest
acquisitions of human knowledge." There has been no
point of intellectual vantage reached which is more inspiring.
It is so comprehensive that it enters into all realms of thought.
Weismann expresses the opinion that ''the theory of descent
is the most progressive step that has been taken in the devel-
opment of human knowledge," and says that this position
"is justified, it seems to me, even by this fact alone: that the
evolution idea is not merely a new light on the special region
of biological sciences, zoology and botany, but is of quite
general importance. The conception of an evolution of life
upon the earth reaches far beyond the bounds of any sin-

ORGANIC EVOLUTION 373

gle science, and influences our whole realm of thought. It
means nothing less than the elimination of the miraculous
from our knowledge of nature, and the placing of the phe-
nomena of life on the same plane as the other natural proc-
esses, that is, as having been brought about by the same
forces and being subject to the same laws."

One feature of the doctrine is very interesting; it has
enabled anatomists to predict that traces of certain structures
not present in the adult will be found in the embryonic condi-
tion of higher animals, and by the verification of these predic-
tions, it receives a high degree of plausibility. The presence
of an OS centrale in the human wrist was predicted, and after-
ward found, as also the presence of a rudimentary thirteenth
rib in early stages of the human body. The predictions, of
course, are chiefly technical, but they are based on the idea
of common descent and adaptation.

It took a long time even for scientific men to arrive at a
belief in the continuity of nature, and having arrived there,
it is not easy to surrender it. There is no reason to think
that the continuity is broken in the case of man's develop-
ment. Naturalists have now come to accept as a mere state-
ment of a fact of nature that the vast variety of forms of life
upon our globe has been produced by a process of evolution.
If this position be admitted, the next question would be,
What are the factors which have been operative to bring this
about? This brings us naturally to discuss the theories of
evolution.

CHAPTER XVII

THEORIES OF EVOLUTION: LAMARCK, DARWIN

The impression so generally entertained that the doctrine
of organic evolution is a vague hypothesis, requiring for its
support great stretches of the imagination, gives way upon an
examination of the facts, and we come to recognize that it is
a well-founded theory, resting upon great accumulations of
evidence. If the matter could rest here, it would be rela-
tively simple; but it is necessary to examine into the causes
of the evolutionary process. While scientific observation has
shown that species are not fixed, but undergo transforma-
tions of considerable extent, there still remains to be accounted
for the way in which these changes have been produced.

One may assume that the changes in animal life are the
result of the interaction of protoplasm and certain natural
agencies in its surroundings, but it is evidently a very diffi-
cult matter to designate the particular agencies or factors of
evolution that have operated to bring about changes in spe-
cies. The attempts to indicate these factors give rise to differ-
ent theories of evolution, and it is just here that the contro-
versies concerning the subject come in. We must remember,
however, that to-day the controversies about evolution are
not as to whether it was or was not the method of creation,
but as to the factors by which the evolution of different
forms was accomplished. Says Packard: "We are all evo-
lutionists, though we may differ as to the nature of the
efficient causes."

Of the various theories which had been advanced to

374

THEORIES OF LAMARCK AND DARWIN 375

account for evolution, up to the announcement of the muta-
tion-theory of De Vries in 1900, three in particular had
commanded the greatest amount of attention and been the
field for varied and extensive discussion. These are the
theories of Lamarck, Darwin, and Weismann. They are
comprehensive theories, dealing with the process as a whole.
Most of the others are concerned with details, and emphasize
certain phases of the process.

Doubtless the factors that have played a part in molding
the forms that have appeared in the procession of life upon
our globe have been numerous, and, in addition to those that
have been indicated, Osbom very aptly suggests that there
may be undiscovered factors of evolution. Within a few
years De Vries has brought into prominence the idea of sudden
transformations leading to new species, and has accounted
for organic evolution on that basis. Further consideration of
this theory, however, will be postponed, while in the present
chapter we shall endeavor to bring out the salient features
of the theories of Lamarck and Darwin, without going into
much detail regarding them.

Lamarck

Lamarck was the first to give a theory of evolution that
has retained a place in the intellectual world up to the present
time, and he may justly be regarded as the founder of that
doctrine in the modern sense. The earlier theories w^ere
more restricted in their reach than that of Lamarck. Eras-
mus Darwin, his greatest predecessor in this field of thought,
announced a comprehensive theory, which, while suggestive
and forceful in originality, was diffuse, and is now only of
historical interest. The more prominent writers on evo-
lution in the period prior to Lamarck will be dealt with in
the chapter on the Rise of Evolutionary Thought.

376 BIOLOGY AND ITS MAKERS

Lamarck was bom in 1744, and led a quiet, monotonous
life, almost pathetic on account of his struggles with poverty,
and the lack of encouragement and proper recognition by his
contemporaries. His life was rendered more bearable, how-
ever, even after he was overtaken by complete blindness,
by the intellectual atmosphere that he created for himself,
and by the superb confidence and affection of his devoted
daughter Comelie, who sustained him and made the truthful
prediction that he would be recognized by posterity (" La
posterite vous honor era^^).

His Family. — He came of a military family possessing
some claims to distinction. The older name of the family
had been de Monet, but in the branch to which Lamarck
belonged the name had been changed to de Lamarque, and
in the days of the first Republic was signed plain I^amarck
by the subject of this sketch. Jean Baptiste Lamarck was
the eleventh and last child of his parents. The other male
members of the family having been provided with military
occupations, Jean was selected by his father, although
against the lad's own wish, for the clerical profession, and ac-
cordingly was placed in the college of the Jesuits at Amiens.
He did not, however, develop a taste for theological studies,
and after the death of his father in 1760 "nothing could
induce the incipient abbe, then seventeen years of age,
longer to wear his bands."

His ancestry asserted itself, and he forsook the college to
follow the French army that was then campaigning in Ger-
many. Mounted on a broken-down horse which he had suc-
ceeded in buying with his scanty means, he arrived on the
scene of action, a veritable raw recruit, appearing before
Colonel Lastic, to whom he had brought a letter of recom-
mendation.

Military Experience. — The Colonel would have liked to
be rid of him, but owing to Lamarck's persistence, assigned

THEORIES OF LAMARCK AND DARWIN 377

him to a company; and, being mounted, Lamarck took rank
as a sergeant. During his first engagement his company
was exposed to the direct fire of the enemy, and the officers
one after another were shot until Lamarck by order of suc-
cession was in command of the fourteen remaining gren-
adiers. Akhough the French army retreated, Lamarck
refused to move with his squad until he received directions
from headquarters to retire. In this his first battle he
showed the courage and the independence that characterized
him in later years.

Adopts Natural Science. — An injury to the glands of the
neck, resulting from being lifted by the head in sport by one
of his comrades, unfitted him for military life, and he went to
Paris and began the study of medicine, supporting himself
in the mean time by working as a bank clerk. It was in his
medical course of four years' severe study that Lamarck
received the exact training that was needed to convert his
enthusiastic love for science into the working powers of an
investigator. He became especially interested in botany,
and, after a chance interview with Rousseau, he determined
to follow the ruling passion of his nature and devote himself
to natural science. After about nine years' work he published,
in 1778, his Flora of France, and in due course was appointed
to a post in botany in the Academy of Sciences. He did not
hold this position long, but left it to travel with the sons
of Buffon as their instructor. This agreeable occupation
extended over two years, and he then returned to Paris, and
soon after was made keeper of the herbarium in the Royal
Garden, a subordinate position entirely beneath his merits.
Lamarck held this poorly paid position for several years, and
was finally relieved by being appointed a professor in the
newly established Jardin des Plantes.

He took an active part in the reorganization of the Royal
Garden (Jardin du Roi) into the Jardin des Plantes. When,

378 BIOLOGY AND ITS MAKERS

during the French Revolution, everything that was suggestive
of royalty became obnoxious to the people, it was Lamarck
who suggested in 1790 that the name of the King's Garden
be changed to that of the Botanical Garden (Jardin des
Plantes). The Royal Garden and the Cabinet of Natural
History were combined, and in 1793 the name Jardin des
Plantes proposed by Lamarck was adopted for the in-
stitution.

It was through the endorsements of Lamarck and Geoffroy
Saint-Hilaire that Cuvier was brought into this great scientific
institution; Cuvier, who was later to be advanced above him
in the Jardin and in public favor, and who was to break
friendship with Lamarck and become the opponent of his
views, and who also was to engage in a memorable debate
with his other supporter, Saint-Hilaire.

The portrait of Lamarck shown in Fig. 112 is one not
generally known. Its date is undetermined, but since it was
published in Thornton's British Plants in 1805, we know
that it was painted before the publication of Lamarck's
Philosophie Zoologique, and before the full force of the cold-
ness and heartless neglect of the world had been experienced.
In his features we read supremacy of the intellect, and the
unflinching moral courage for which he was notable. La-
marck has a more hopeful expression in this portrait than in
those of his later years.

Lamarck Changes from Botany to Zoology. — Until 1794,
when he was fifty years of age, Lamarck was devoted to
botany, but on being urged, after the reorganization of the
Jardin du Roi, to take charge of the department of inverte-
brates, he finally consented and changed from the study of
plants to that of animals. This change had profound in-
fluence in shaping his ideas. He found the invertebrates in
great confusion, and set about to bring order out of chaos,
an undertaking in which, to his credit be it acknowledged,

THEORIES OF LAMARCK AND DARWIN 379

he succeeded. The fruit of his labors, the Natural His-
tory of Invertebrated Animals {Historie naturelle des Ani-

FiG. 112. — Lamarck, 1744-1829.
From Thornton's British Plants, 1805.

maux sans Vertebres, 181 5-1822), became a work of great
importance. He took hold of this work, it should be re-
membered, as an expert observer, trained to rigid analysis

38o BIOLOGY AND ITS MAKERS

by his previous critical studies in botany. In the progress
of the work he was impressed with the differences in ani-
mals and the difficulty of separating one species from an-
other. He had occasion to observe the variations produced
in animals through the influence of climate, temperature,
moisture, elevation above the sea-level, etc.

He observed also the effects of use and disuse upon the
development of organs: the exercise of an organ leading to
its greater development, and the disuse to its degeneration.
Numerous illustrations are cited by Lamarck which serve to
make his meaning clear. The long legs of wading birds
are produced and extended by stretching to keep above the
water; the long neck and bill of storks are produced by their
habit of life; the long neck of the giraffe is due to reaching
for fohage on trees; the web-footed birds, by spreading
the toes when they strike the water, have stimulated the
development of a membrane between the toes, etc. In the
reverse direction, the loss of the power of flight in the ''wing-
less" bird of New Zealand is due to disuse of the wings;
while the loss of sight in the mole and in blind cave animals
has arisen from lack of use of eyes.

The changes produced in animal organization in this
way were believed to be continued by direct inheritance and
improved in succeeding generations.

He believed also in a perfecting principle, tending to
improve animals — a sort of conscious endeavor on the part
of the animal playing a part in its better development. Fi-
nally, he came to believe that the agencies indicated above
were the factors of the evolution of life.

His Theory of Evolution. — All that Lamarck had written
before he changed from botany to zoology (1794) indicates
his belief in the fixity of species, which was the prevailing
notion among naturalists of the period. Then, in 1800, we
find him apparently all at once expressing a contrary opinion,

THEORIES OF LAMARCK AND DARWIN 381

and an opinion to which he held unwaveringly to the close
of his life. It would be of great interest to determine when
Lamarck changed his views, and upon what this radical rever-
sal of opinion was based; but we have no sure record to
depend upon. Since his theory is developed chiefly upon
considerations of animal life, it is reasonable to assume that
his evolutionary ideas took form in his mind after he began
the serious study of animals. Doubtless, his mind having
been prepared and his insight sharpened by his earlier studies,
his observations in a new field supplied the data which led
him directly to the conviction that species are unstable.
As Packard, one of his recent biographers, points out, the
first expression of his new views of which we have any record
occurred in the spring of 1800, on the occasion of his opening
lecture to his course on the invertebrates. This avowal of
belief in the extensive alteration of species was published in
1801 as the preface to his Systeme des Animaux sans
Vertehres. Here also he foreshadowed his theory of evo-
lution, saying that nature, having formed the simplest
organisms, ''then with the aid of much time and favor-
able circumstances . . . formed all the others." It has
been generally believed that Lamarck's first public ex-
pression of his views on evolution was published in 1802
in his Recherches sur V Organisation des Corps Vivans,
but the researches of Packard and others have established
the earlier date.

Lamarck continued for several years to modify and am-
plify the expression of his views. It is not necessary, how-
ever, to follow the molding of his ideas on evolution as
expressed in the opening lectures to his course in the years
1 80c, 1802, 1803, and 1806, since we find them fully elab-
orated in his Philosophie Zoologique, published in 1809,
and this may be accepted as the standard source for the
study of his theory. In this work he states two propositions

382 BIOLOGY AND ITS MAKERS

under the name of laws, which have been translated by
Packard as follows!

" First Law : In every animal which has not exceeded the
term of its development, the more frequent and sustained
use of any organ gradually strengthens this organ, develops
and enlarges it, and gives it a strength proportioned to the
length of time of such use; while the constant lack of use of
such an organ imperceptibly weakens it, causing it to become
reduced, progressively diminishes its faculties, and ends in
its disappearance.

" Second Law : Everything which nature has caused
individuals to acquire or lose by the influence of the circum-
stances to which their race may be for a long time exposed,
and consequently by the influence of the predominant use of
such an organ, or by that of the constant lack of use of such
part, it preserves by heredity and passes on to the new indi-
viduals which descend from it, provided that the changes
thus acquired are common to both sexes, or to those which
have given origin to these new individuals.

'' These are the two fundamental truths which can be mis-
understood only by those who have never observed or
followed nature in its operations," etc. The first law
embodies the principle of use and disuse, the second law that
of heredity.

In 1815 his theory received some extensions of minor
importance. The only points to which attention need be
called are that he gives four laws instead of two, and that a
new feature occurs in the second law in the statement that
the production of a new organ is the result of a new need
(besoin) which continues to make itself felt.

Simplified Statement of Lamarck*s Views. — For practical
exposition the theory maybe simplified into two sets of facts:
First, those to be classed under variation; and, second, those
under heredity. Variations of organs, according to Lamarck,,

THEORIES OF LAMARCK AND DARWIN ^8^

arise in animals mainly through use and disuse, and new
organs have their origin in a physiological need. A new need
felt by the animal impresses itself on the organism, stimulating
growth and adaptations in a particular direction. This part
of Lamarck's theory has been subjected to much ridicule.
The sense in which he employs the word besoin has been
much misunderstood; when, however, we take into ac-
count that he uses it, not merely as expressing a wish or
desire on the part of the animal, but as the reflex action
arising from new conditions, his statement loses its alleged
grotesqueness and seems to be founded on sound physiology.

Inheritance. — Lamarck's view of heredity was uncritical;,
according to his conception, inheritance was a simple, direct
transmission of those superficial changes that arise in organs
within the lifetime of an individual owing to use and disuse.
It is on this question of the direct inheritance of variations
acquired in the lifetime of an individual that his theory has
been the most assailed. The behef in the inheritance of
acquired characteristics has been so undermined by experi-
mental evidence that at the present time we can not point
to 'a single unchallenged instance of such inheritance. But,
while Lamarck's theory has shown weakness on that side,,
his ideas regarding the production of variations have been
revived and extended.

Variation. — The more commendable part of his theory
is the attempt to account for variation. Darwin assumed
variation, but Lamarck attempted to account for it, and in
this feature many discerning students maintain that the
theory of Lamarck is more philosophical in its foundation
than that of Darwin.

In any theory of evolution we must deal with the variation
of organisms and heredity, and thus we observe that the two
factors discussed by Lamarck are basal. Although it must
be admitted that even to-day we know little about either

384 BIOLOGY AND ITS MAKERS

variation or heredity, they remain basal factors in any theory
of evolution.

Time and Favorable Conditions. — Lamarck supposed a
very long time was necessary to bring about the changes which
have taken place in animals. The central thought of time
and favorable conditions occurs again and again in his
writings. The following quotation is interesting as coming
from the first announcement of his views in 1800:

*' It appears, as I have already said, that time and favorable
conditions are the two principal means which nature has
employed in giving existence to all her productions. We
know that for her time has no limit, and that consequently
she has it always at her disposal.

"As to the circumstances of which she has had need and
of which she makes use every day in order to cause her pro-
ductions to vary, we can say that in a manner they are
inexhaustible.

"The essential ones arising from the influence and from
all the environing media, from the diversity of local causes,
of habits, of movements, of action, finally of means of living,
of preserving their lives, of defending themselves, of mul-
tiplying themselves, etc. Moreover, as the result of these
different influences, the faculties, developed and strengthened
by use, become diversified by the new habits maintained for
long ages, and by slow degrees the structure, the consistence —
in a word, the nature, the condition of the parts and of the
organs consequently participating in all these influences,
became preserved and were propagated by heredity (genera-
tion)." (Packard's translation.)

Salient Points. — The salient points in Lamarck's theory
may be compacted into a single sentence: It is a theory of
the evolution of animal life, depending upon variations
brought about mainly through use and disuse of parts,
and also by responses to external stimuli, and the direct

THEORIES OF LAMARCK AND DARWIN 385

inheritance of the same. His theory is comprehensive,
so much so that he includes mankind in his general con-
clusions.

Lamarck supposed that an animal having become
adapted to its surroundings would remain relatively stable
as to its structure. To the objection raised by Cuvier that
animals from Egypt had not changed since the days when
they were preserved as mummies, he replied that the climate
of Egypt had remained constant for centuries, and therefore
no change in its fauna was to be expected.

Species. — Since the question of the fixity of species is the
central one in theories of evolution, it will be worth while to
quote Lamarck's definition of species: "All those who have
had much to do with the study of natural history know that
naturalists at the present day are extremely embarrassed in
defining what they mean by the word species. . . . We call
species every collection of individuals which are alike or
almost so, and we remark that the regeneration of these
individuals conserves the species and propagates it in con-
tinuing successively to reproduce similar individuals." He
then goes on with a long discussion to show that large collec-
tions of animals exhibit a great variation in species, and that
they have no absolute stability, but "enjoy only a relative
stabihty."

Herbert Spencer adopted and elaborated the theory of
Lamarck. He freed it from some of its chief crudities, such
as the idea of an innate tendency toward perfection. In
many controversies Mr. Spencer defended the idea of the
transmission of acquired characters. The ideas of Lamarck
have, therefore, been transmitted to us largely in the Spence-
rian mold and in the characteristic language of that great
philosopher. There has been but little tendency to go to
Lamarck's original writings. Packard, whose biography of
Lamarck appeared in igci, has made a thorough analysis

386 BIOLOGY AND ITS MAKERS

of his, writings and had incidentally corrected several erro-
neous conception.

Neo-Lamarckism. — The ideas of Lamarck regarding the
beginning of variations have been revived and accorded much
respect under the designation of Neo-Lamarckism. The
revival of Lamarckism is especially owing to the palaeon-
tological investigations of Cope and Hyatt. The work of
E. D. Cope in particular led him to attach importance to the
effect of mechanical and other external causes in producing
variation, and he points out many instances of use-inher-
itance. Neo-Lamarckism has a considerable following; it
is a revival of the fundamental ideas of Lamarck.

Darwin's Theory

While Lamarck's theory rests upon two sets of facts,
Darwin's is founded on three: viz., the facts of variation,
of inheritance, and of natural selection. The central feature
of his theory is the idea of natural selection. No one else
save Wallace had seized upon this feature when Darwin
made it the center of his system. On account of the part
taken by Wallace simultaneously with Darwin in announcing
natural selection as the chief factor of evolution, it is appro-
priate to designate this contribution as the Darwin- Wallace
principle of natural selection. The interesting connection
between the original conclusions of Darwin and Wallace is
set forth in Chapter XIX.

Variation. — It will be noticed that two of the causes
assigned by Darwin are the same as those designated by La-
marck, but their treatment is quite different. Darwin (Fig.
1 13) assumed variation among animals and plants without at-
tempting to account for it, while Lamarck undertook to state
the particular influences which produce variation, and al-
though we must admit that Lamarck was not entirely sue-

Fig. 113. — Charles Darwin, 1809-1882.

S^^ BIOLOGY AND ITS MAKERS

cessful in this attempt, the fact that he undertook the task
places his contribution at the outset on a very high plane.

The existence of variation as established by observation
is unquestioned. No two living organisms are exactly alike
at the time of their birth, and even if they are brought up
together under identical surroundings they vary. The varia-
tion of plants and animals under domestication is so con-
spicuous and well known that this kind of variation was the
first to attract attention. It was asserted that these varia-
tions were perpetuated because the forms had been protected
by man, and it was doubted that animals varied to any con-
siderable extent in a state of nature. Extended collections
and observ^ations in field and forest have, however, set this
question at rest.

If crows or robins or other birds are collected on an exten-
sive scale, the variability of the same species will be evident.
Many examples show that the so-called species differ greatly
in widely separated geographical areas, but collections from
the intermediate territory demonstrate that the variations
are connected by a series of fine gradations. If, for illustra-
tion, one should pass across the United States from the
Atlantic to the Pacific coast, collecting one species of bird,
the entire collection would exhibit wide variations, but the
extremes would be connected by intermediate forms.

The amount of variation in a state of nature is much
greater than was at first supposed, because extensive collec-
tions were lacking, but the existence of wide variation is now
established on the basis of observation. This fact of varia-
tion among animals and plants in the state of nature is
unchallenged, and affords a good point to start from in con-
sidering Darwinism.

Inheritance. — The idea that these variations are inher-
ited is the second point. But what particular variations will
be preserved and fostered by inheritance, and on what

THEORIES OF LAMARCK AND DARWIN 389

principle they will be selected, is another question — and a
notable one. Darwin's reply was that those variations which
are of advantage to the individual will be the particular ones
selected by nature for inheritancig. While Darwin implies
the inheritance of acquired characteristics, his theory of
heredity was widely different from that of Lamarck. Dar-
win's theory of heredity, designated the provisional theory of
pangenesis, has been already considered (see Chapter XIV).

Natural Selection. — Since natural selection is the main
feature of Darwin's doctrine, we must devote more time to
it. Darwin frequently complained that very few of his
critics took the trouble to find out what he meant by the term
natural selection. A few illustrations will make his meaning
clear. Let us first think of artificial selection as it is applied
by breeders of cattle, fanciers of pigeons and of other fowls,
etc. It is well known that by selecting particular variations
in animals and plants, even when the variations are slight,
the breeder or the horticulturalist will be able in a short
time to produce new races of organic forms. This artificial
selection on the part of man has given rise to the various
breeds of dogs, the 150 different kinds of pigeons, etc., all
of which breed true. The critical question is. Have these all
an individual ancestral form in nature ? Observation shows
that many different kinds — as pigeons — may be traced back
to a single ancestral form, and thus the doctrine of the fixity
of species is overthrown.

Now, since it is demonstrated by observation that varia-
tions occur, if there be a selective principle at work in
nature, effects similar to those caused by artificial selec-
tion will be produced. The selection by nature of the forms
fittest to survive is what Darwin meant by natural selection.
We can never understand the application, however, unless
we take into account the fact that while animals tend to
multiply in geometrical progression, as a matter of fact the

390 BIOLOGY AND ITS MAKERS

number of any one kind remains practically constant.
Although the face of nature seems undisturbed, there is
nevertheless a struggle for existence among all animals.

This is easily illustrated when we take into account the
breeding of fishes. The trout, for illustration, lays from 60,000
to 100,000 eggs. If the majority of these arrived at maturitv
and gave rise to progeny, the next generation would represent
a prodigious number, and the numbers in the succeeding
generations would increase so rapidly that soon there would
not be room in the fresh waters of the earth to contain their
descendants. What becomes of the immense number of
fishes that die ? They fall a prey to others, or they are not
able to get food in competition with other more hardy rela-
tives, so that it is not a matter of chance that determines
which ones shall survive; those which are the strongest, the
better fitted to their surroundings, are the ones which will
be perpetuated.

The recognition of this struggle for existence in nature,
and the consequent survival of the fittest, shows us more
clearly what is meant by natural selection. Instead of man
making the selection of those particular forms that are to
survive, it is accomplished in the course of nature. This is
natural selection.

Various Aspects of Natural Selection. — Further illustra-
tions are needed to give some idea of the various phases of
natural selection. Speed in such animals as antelopes may
be the particular thing which leads to their protection. It
stands to reason that those with the greatest speed would
escape more readily from their enemies, and would be the
particular ones to survive, while the weaker and slower ones
would fall victims to their prey. In all kinds of strain due to
scarcity of food, inclemency of weather, and other untoward
circumstances, the forms which are the strongest, physio-
logically speaking, will have the best chance to weather the

THEORIES OF LAMARCK AND DARWIN 391

Strain and to survive. As another illustration, Darwin
pointed out that natural selection had produced a long-legged
race of prairie wolves, while the timber wolves, which have
less occasion for running, are short-legged.

We can also see the operation of natural selection in the
production of the sharp eyes of birds of prey. Let us con-
sider the way in which the eyes of the hawk have beeh per-
fected by evolution. Natural selection compels the eye to
come up to a certain standard. Those hawks that are bom
with weak or defective vision cannot cope with the conditions
under which they get their food. The sharp-eyed forms
would be the first to discern their prey, and the most sure in
seizing upon it. Therefore, those with defective vision or
with vision that falls below the standard will be at a very
great disadvantage. The sharp-eyed forms will be preserved
by a selective process. Nature selects, we may say, the
keener-eyed birds of prey for survival, and it is easy to see
that this process of natural selection would establish and
maintain a standard of vision.

But natural selection tends merely to adapt animals to
their surroundings, and does not always operate in the direc-
tion of increasing the efficiency of the organ. We take an-
other illustration to show how Darwin explains the origin of
races of short-winged beetles on certain oceanic islands.
Madeira and other islands, as Kerguelen island of the Indian
Ocean, are among the most windy places in the world. The
strong-winged beetles, being accustomed to disport them-
selves in the air, would be carried out to sea by the sudden
and violent gales which sweep over those islands, while the
weaker-winged forms would be left to perpetuate their kind.
Thus, generation after generation, the strong-winged beetles
would be ehminated by a process of natural selection, and
there would be left a race of short-winged beetles derived
from long-winged ancestors. In this case the organs are

392 BIOLOGY AND ITS MAKERS

reduced in their development, rather than increased; but
manifestly the short -winged race of beetles is better adapted
to Hve under the particular conditions that surround their
life in these islands.

While this is not a case of increase in the particular organ,
it illustrates a progressive series of steps whereby the organ-
ism becomes better adapted to its surroundings. A similar
instance is found in the suppression of certain sets of organs
in internal parasites. For illustration, the tapeworm loses
particular organs of digestion for which it does not have
continued use ; but the reproductive organs, upon which the
continuance of its life depends, are greatly increased. Such
cases as the formation of short- winged beetles show us that
the action of natural selection is not always to preserve what
we should call the best, but simply to preserve the fittest.
Development, therefore, under the guidance of natural selec-
tion is not always progressive. Selection by nature does
not mean the formation and preservation of the ideally per-
fect, but merely the survival of those best fitted to their
environment.

Color. — The various ways in which natural selection acts
are exceedingly diversified. The colors of animals may be
a factor in their preservation, as the stripes on the zebra
tending to make it inconspicuous in its surroundings. The
stripes upon the sides of tigers simulate the shadows cast by
the jungle grass in which the animals live, and serve to con-
ceal them from their prey as well as from enemies. Those
animals that assume a white color in winter become thereby
less conspicuous, and they are protected by their coloration.

As further illustrating color as a factor in the preserva-
tion of animals, we may cite a story originally told by
Professor E. S. Morse. When he was collecting shells on the
white sand of the Japanese coast, he noticed numerous white
tiger-beetles, which could scarcely be seen against the white

THEORIES OF LAMARCK AND DARWIN 393

background. They could be detected chiefly by their
shadows when the sun was shining. As he walked along
the coast he came to a wide band of lava which had flowed
from a crater across the intervening country and plunged
into the sea, leaving a broad dark band some miles in breadth
across the white sandy beach. As he passed from the white
sand to the dark lava, his attention was attracted to a tiger-
beetle almost identical with the white one except as to color.
Instead of being white, it was black. He found this broad,
black band of lava inhabited by the black tiger beetle, and
found very few, if any, of the white kind. This is a striking
illustration of what has occurred in nature. These two
beetles are of the same species, and in examining the condi-
tions under which they grow, it is discovered that out of the
eggs laid by the original white forms, there now and then
appears one of a dusky or black color. Consider how con-
spicuous this dark object would be against the white back-
ground of sand. It would be an easy mark for the birds
of prey that fly about, and therefore on the white surface
the black beetles would be destroyed, while the w^hite ones
would be left. But on the black background of lava the
conditions are reversed. There the white forms would be the
conspicuous ones; as they wandered upon the black surface,
they would be picked up by birds of prey and the black ones
would be left. Thus we see another instance of the operation
of natural selection.

Mimicry. — We have, likewise, in nature a great number
of cases that are designated mimicry. For illustration, cer-
tain caterpillars assume a stiff position, resembling a twig
from a branch. We have also leaf-like butterflies. The Kal-
lima of India is a conspicuous illustration of a butterfly
having the upper surface of its wings bright-colored, and the
lower surface dull. When it settles upon a twig the wings
are closed and the under- sides have a mark across them

394 BIOLOGY AND ITS MAKERS

resembling the mid-rib of a leaf, so that the whole butterfly
in the resting position becomes inconspicuous, being pro-
tected by mimicry.

One can readily see how natural selection would be evoked
in order to explain this condition of affairs. Those forms
that varied in the direction of looking like a leaf would be
the most perfectly protected, and this feature being fostered
by natural selection, would, in the course of time, produce a
race of butterflies the resemblance of whose folded wings to
a leaf would serve as a protection from enemies.

It may not be out of place to remind the reader that the
illustrations cited are introduced merely to elucidate Dar-
win's theory and the writer is not committed to accepting
them as explanations of the phenomena involved. He is
not unmindful of the force of the criticisms against the ade-
quacy of natural selection to explain the evolution of all
kinds of organic structures.

Many other instances of the action of color might be
added, such as the wearing of warning colors, those colors
which belong to butterflies, grubs, and other animals that
have a noxious taste. These warning colors have taught
birds to leave alone the forms possessing those colors. Some-
times forms which do not possess a disagreeable taste
secure protection by mimicking the colors of the noxious
varieties.

Sexual Selection. — There is an entirely different set of
cases which at first sight would seem difficult to explain on
the principle of selection. How, for instance, could we
explain the feathers in the tails of the birds of paradise, or
that peculiar arrangement of feathers in the tail of the lyre-
bird, or the gorgeous display of tail-feathers of the male
peacock? Here Mr. Darwin seized upon a selective prin-
ciple arising from the influence of mating. The male birds
in becoming suitors for a particular female have been accus-

THEORIES OF LAMARCK AND DARWIN 395

tomed to display their tail-feathers; the one with the most
attractive display excites the pairing instinct in the highest
degree, and becomes the selected suitor. In this way,
through the operation of a form of selection which Darwin
designates sexual selection, possibly such curious adaptations
as the peacock's tail may be accounted for.

It should be pointed out that this part of the theory is
almost wholly discredited by biologists. Experimental evi-
dence is against it. Nevertheless in a descriptive account
of Darwin's theory it may be allowed to stand without
critical comment.

Inadequacy of Natural Selection. — In nature, under the
struggle for existence, the fittest will be preserved; and natural
selection will operate toward the elaboration or the suppres-
sion of certain organs or certain characteristics when the elab-
oration or the suppression is of advantage to the animal form.
Much has been said of ]ate as to the inadequacy of natural
selection. Herbert Spencer and Huxley, both accepting
natural selection as one of the factors, doubted its complete
adequacy.

One point is often overlooked, and should be brought out
with clearness; viz., that Darwin himself was the first to
point out clearly the inadequacy of natural selection as a
universal law for the production of the great variety of
animals and plants. In the second edition of the Origin of
Species he says: "But, as my conclusions have lately been
much misrepresented, and it has been stated that I attribute
the modification of species exclusively to natural selection,
I may be permitted to remark that in the first edition of this
work and subsequently I placed in a most conspicuous
position, — namely, at the close of the introduction — the follow-
ing words: 'I am convinced that natural selection has been
the main, but not the exclusive means of modification.' This
has been of no avail. Great is the power of steady mis-

396 BIOLOGY AND ITS MAKERS

representation. But the history of science shows that for-
tunately this power does not long endure."

The reaction against the all-sufficiency of natural selec-
tion, therefore, is something which was anticipated by Dar-
win, and the quotation made above will be a novelty to many
of our readers who supposed that they understood Darwin's
position.

Confusion between Lamarck's and Darwin's Theories. —
Besides the failure to understand what Darwin has written,
there is great confusion, both in pictures and in writings, in
reference to the theories of Darwin and Lamarck. Poulton
illustrated a state of confusion in one of his lectures on the
theory of organic evolution, and the following instances are
quoted from memory.

We are most of us familiar with such pictures as the
following: A man standing and waving his arms; in the next
picture these arms and hands become enlarged, and in the
successive pictures they undergo transformations into wings,
and the transference is made into a flying animal.

Such pictures are designated ''The origin of flight after
Darwin." The interesting circumstance is this, that the
iUustration does not apply to Darwin's idea of natural selec-
tion at all, but is pure Lamarckism. Lamarck contended
for the production of new organs through the influence of
use and disuse, and this particular illustration refers to that,
and not to natural selection at all.

Among the examples of ridicule to which Darwin's ideas
have been exposed, we cite one verse from the song of Lord
Neaves. His lordship wrote a song with a large number of
verses hitting off in jocular vein many of the claims and
foibles of his time. In attempting to make fun of Darwin's
idea he misses completely the idea of natural selection, but
hits upon the principle enunciated by Lamarck, instead.
He says:

THEORIES OF LAMARCK AND DARWIN 397

"A deer with a neck which was longer by half
Than the rest of his family's — try not to laugh —
By stretching and stretching became a giraffe,
Which nobody can deny."

The clever young woman, Miss Kendall, however, in her
Song oj the Ichthyosaurus, showed clearness in grasping
Darwin's idea when she wrote:

"Ere man was developed, our brother,
We swam, we ducked, and we dived,
And we dined, as a rule, on each other.
What matter? The toughest survived."

This hits the idea of natural selection. The other two illus-
trations miss it, but strike the principle which was enunciated
by Lamarck. This confusion between Lamarckism and Dar-
winism is very wide-spread.

Darwin's book on the Origin oj Species, published in
1859, was epoch-making. If a group of scholars were asked
to designate the greatest book of the nineteenth century —
that is, the book which created the greatest intellectual stir —
it is likely that a large proportion of them would reply that
it is Darwin's Origin of Species. Its influence was so great
in the different domains of thought that we may observe a
natural cleavage between the thought in reference to nature
between 1859 and all preceding time. His other less widely
known books on Animals and Plants Under Domestication,
the Descent 0} Man, etc., etc., are also important contributions
to the discussion of his theory. A brief account of Darwin,
the man, will be found in Chapter XIX.

CHAPTER XVIII

THEORIES OF EVOLUTION CONTINUED:
WEISMANN, DE VRIES

Weism Ann's views have passed through various stages of
remodeHng since his first pubhc championship of the Theory
of Descent on assuming, in 1867, the position of professor of
zoology in the University of Freiburg. Some time after that
date he originated his now famous theory of heredity, which
has been retouched, from time to time, as the resuh of
aggressive criticism from others, and the expansion of his
own mental horizon. As he said in 1904, regarding his
lectures on evolution which have been delivered almost reg-
ularly every year since 1880, they "were gradually modified
in accordance with the state of my knowledge at the time,
so that they have been, I may say, a mirror of my own intel-
lectual evolution."

Passing over his book. The Germ Plasm, published in
English in 1893, we may fairly take his last book. The
Evolution Theory, 1904, as the best exposition of his con-
clusions. The theoretical views of Weismann have been
the field of so much strenuous controversy that it will be well
perhaps to take note of the spirit in which they have been
presented. In the preface of his book just mentioned, he
says: "I make this attempt to sum up and present as a har-
monious whole the theories which for forty years I have been
gradually building up on the basis of the legacy of the great
workers of the past, and on the results of my own investiga-

398

THEORIES OF WEISMANN AND DE VRIES 399

tions and those of my fellow-workers, not because I regard
the picture as incomplete or incapable of improvement, but
because I believe its essential features to be correct, and
because an eye-trouble which has hindered my work for
many years makes it uncertain whether I shall have much
more time and strength granted to me for its further elabora-
tion."

The germ-plasm theory is primarily a theory of heredity,
and only when connected with other considerations does it
become the full-fledged theory of evolution known as Weis-
mannism. The theory as a whole involves so many intricate
details that it is difficult to make a clear statement of it for
general readers. If in considering the theories of Lamarck
and Darwin it was found advantageous to confine attention
to salient points and to omit details, it is all the more essential
to do so in the discussion of Weismann's theory.

In his prefatory note to the Enghsh edition of The
Evolution Theory Thomson, the translator, summarizes Weis-
mann's especial contributions as: '' (i) the illumination of the
evolution process with a wealth of fresh illustrations; (2)
the vindication of the 'germ-plasm' concept as a valuable
working hypothesis; (3) the final abandonment of any
assumption of transmissible acquired characters; (4) a
further analysis of the nature and origin of variations; and
(5), above all, an extension of the selection principle of
Darwin and Wallace, which finds its logical outcome in the
suggestive theory of germinal selection."

Continuity of the Germ-Plasm. — Weismann's theory is
designated that of continuity of the germ-plasm, and in con-
sidering it we must first give attention to his conception of
the germ-plasm. As is well known, animals and plants
spring from germinal elements of microscopic size; these are,
in plants, the spores, the seeds, and their fertilizing agents;
and, in animals, the eggs and the sperms. Now, since all

400 BIOLOGY ANY ITS MAKERS

animals, even the highest developed, begin in a fertilized egg,
that structure, minute as it is, must contain all hereditary
qualities, since it is the only material substance that passes
from one generation to another. This hereditary substance
is the germ-plasm. It is the living, vital substance of organ-
isms that takes part in the development of new generations.

Naturalists are agreed on this point, that the more com-
plex animals and plants have been derived from the simpler
ones; and, this being accepted, the attention should be fixed
on the nature of the connection between generations during
their long line of descent. In the reproduction of single-
celled organisms, the substance of the entire body is divided
during the transmission of life, and the problem both of
heredity and origin is relatively simple. It is clear that in
these single-celled creatures there is unbroken continuity of
body-substance from generation to generation. But in the
higher animals only a minute portion of the organism is
passed along.

Weismann points out that the many-celled body was
gradually produced by evolution; and that in the trans-
mission of life by the higher animals the continuity is not
between body-cells and their like, but only between ger-
minal elements around which in due course new body-cells
are developed. Thus he regards the body-cells as constitut-
ing a sort of vehicle within which the germ-cells are carried.
The germinal elements represent the primordial substance
around which the body has been developed, and since in all
the long process of evolution the germinal elements have been
the only form of connection between different generations,
they have an unbroken continuity.

This conception of the continuity of the germ-plasm is
the foundation of Weismann' s doctrine. As indicated before,
the general way in which he accounts for heredity is that the
offspring is like the parent because it is composed of some of

THEORIES OF WEISMANN AND DE VRIES 401

the same stuff. The rise of the idea of germinal continuity
has been indicated in Chapter XIV, where it was pointed out
that Weismann was not the originator of the idea, but he is nev-
ertheless the one who has developed it the most extensively.

Complexity of the Germ-Plasm. — The germ-plasm has
been molded for so many centuries by external circum-
stances that it has acquired an organization of great com-
plexity. This appears from the following considerations:
Protoplasm is impressionable; in fact, its most characteristic
feature is that it responds to stimulation and modifies itself
accordingly. These subtle changes occurring within the
protoplasm affect its organization, and in the long run it is
the summation of experiences that determines what the pro-
toplasm shall be and how it will behave in development.
Two masses of protoplasm differ in capabilities and poten-
tialities according to the experiences through which they have
passed, and no two will be absolutely identical. All the time
the body was being evolved the protoplasm of the germinal
elements was being molded and changed, and these ele-
ments therefore possess an inherited orgnization of great
complexity.

When the body is built anew from the germinal ele-
ments, the derived qualities come into play, and the whole
process is a succession of responses to stimulation. This is
in a sense, on the part of the protoplasm, a repeating of its
historical experience. In building the organism it does not
go over the ground for the first time, but repeats the activities
which it took centuries to acquire.

The evident complexity of the germ-plasm made it
necessary for Weismann, in attempting to explain inheritance
in detail, to assume the existence of distinct vital units within
the protoplasm of the germinal elements. He has invented
names for these particular units as biophors, the elementary
vital units, and their combination into determinants, the

402 BIOLOGY AND ITS MAKERS

latter being united into ids, idants, etc. The way in which
he assumes the interactions of these units gives to his theory
a highly speculative character. The conception of the
complex organization of the germ-plasm which Weismann
reached on theoretical grounds is now being established on
the basis of observation (see Chapter XIV, p. 313).

The Origin of Variations. — The way in which Weismann
accounts for the origin of variation among higher animals
is both ingenious and interesting. In all higher organisms
the sexes are separate, and the reproduction of their kind is
a sexual process. The germinal elements involved are seeds
and pollen, eggs and sperms. In animals the egg bears all
the hereditary qualities from the maternal side, and the
sperm those from the paternal side. The intimate mixture
of these in fertilization gives great possibilities of variations
arising from the different combinations and permutations of
the vital units within the germ-plasm.

This union of two germ-plasms Weismann calls amphi-
mixis, and for a long time he maintaine 1 that the purpose
of sexual reproduction in nature is to give origin to varia-
tions. Later he extended his idea to include a selection,
mainly on the basis of nutrition, among the vital elements
composing the germ-plasm. This is germinal selection,
which aids in the production of variations.

In The Evolution Theory, volume II, page 196, he says:
"Now that I understand these processes more clearly, my
opinion is that the roots of all heritable variation lie in the
germ-plasm; and, furthermore, that the determinants are
continually oscillating hither and thither in response to
very minute nutritive changes and are readily compelled
to variation in a definite direction, which may ultimately lead
to considerable variations in the structure of the species, if
they are favored by personal selection, or at least if they are
not suppressed by it as prejudicial."

HEORIES OF WEISMANN AND DE VRIES 403

But while sexual reproduction may be evoked to explain
the origin of variation in higher animals, Weismann thought
it was not applicable to the lower ones, and he found himself
driven to assume that variation in single-celled organisms is
owing to the direct influence of environment upon them,
and thus he had an awkward assumption of variations arising
in a different manner in the higher and in the simplest organ-
isms. If I correctly understand his present position, the
conception of variation as due to the direct influence of
environment is being surrendered in favor of the action of
germinal selection among the simplest organisms.

Extension of the Principle of Natural Selection. — These
variations, once started, will be fostered by natural selection
provided they are of advantage to the organism in its struggle
for existence. It should be pointed out that Weismann is a
consistent Darwinian; he not only adopts the principle of
natural selection, but he extends the field of its operation
from externals to the internal parts of the germinal elements.

"Roux and others have elaborated the idea of a struggle
of the parts within the organism, and of a corresponding
intra-selection ; . . . but Weismann, after his manner, has
carried the selection-idea a step farther, and has pictured
the struggle among the determining elements of the germ-
cell's organization. It is at least conceivable that the stronger
'determinants,' i.e., the particles embodying the rudiments
of certain qualities, will make more of the food-supply than
those which are weaker, and that a selective process will
ensue" (Thomson). This is the conception of germinal
selection.

He has also extended the application of the general
doctrine of natural selection by supplying a great number
of new illustrations.

The whole theory of Weismann is so well constructed
that it is very alluring. Each successive position is worked

404 BIOLOGY AND ITS MAKERS

out with such detail and apt illustration that if one follows
him step by step without dissent on some fundamental prin-
ciple, his conclusion seems justified. As a system it has
been elaborated until it makes a coherent appeal to the
intellect.

Inheritance of Acquired Characters. — Another funda-
mental point in Weismann's theory is the denial that acquired
characters are transmitted from parent to offspring. Prob-
ably the best single discussion of this subject is contained
in his book on The Evolution Theory, 1904, to which readers
are referred.

A few illustrations will be in place. Acquired characters
are any acquisitions made by the body-cells during the
lifetime of an individual. They may be obvious, as skill
in piano-playing, bicycle-riding, etc.; or they may be very
recondite, as turns of the intellect, acquired beliefs, etc.
Acquired bodily characters may be forcibly impressed upon
the organism, as the facial mutilations practiced by certain
savage tribes, the docking of the tails of horses, of dogs, etc.
The question is. Are any acquired characters, physical or
mental, transmitted by inheritance?

Manifestly, it will be difficult to determine on a scientific
basis whether or not such qualities are inheritable. One
would naturally think first of applying the test of experiment
to supposed cases of such inheritances, and this is the best
ground to proceed on.

It has been maintained on the basis of the classical
experiments of Brown-Sequard on guinea-pigs that induced
epilepsy is transmitted to offspring; and, also, on the basis
of general observations, that certain bodily mutilations are
inherited. Weismann's analysis of the whole situation is
very incisive. He experimented by cutting off the tails of
both parents of breeding mice. The experiments were
carried through twenty-two generations, both parents being

THEORIES OF WEISMANN AND DE VRIES 405

deprived of their tails, without yielding any evidence that
the mutilations were inheritable.

To take one other case that is less superficial, it is gener-
ally believed that the thirst for alcoholic liquors has been
transmitted to the children of drunkards, and while Weismann
admits the possibility of this, he maintains that it is owing
to the germinal elements being exposed to the influence of
the alcohol circulating in the blood of the parent or parents;
and if this be the case it would not be the inheritance of an
acquired character, but the response of the organism to a
drug producing directly a variation in the germ-plasm.

Notwithstanding the well-defined opposition of Weismann,
the inheritance of acquired characters is still a mooted ques-
tion. Herbert Spencer argued in favor of it, and during his
lifetime had many a pointed controversy with Weismann.
Eimer stands unalterably against Weismann' s position, and
the Neo-Lamarckians stand for the direct inheritance of use-
ful variations in bodily structure. The question is still
undetermined and is open to experimental observation. In
its present state there are competent observers maintaining
both sides, but it must be confessed that there is not a single
case in which the supposed inheritance of an acquired char-
acter has stood the test of critical examination.

The basis of Weismann' s argument is not difficult to
understand. Acquired characters affect the body-cells, and
according to his view the latter are simply a vehicle for the
germinal elements, which are the only things concerned in
the transmission of hereditary qualities. Inheritance, there-
fore, must come through alterations in the germ-plasm, and
not directly through changes in the body-cells.

Weismann, the Man. — The man who for more than forty
years elaborated and strengthened this theory has recently
(Nov. 1914) passed away at Freiburg. August Weismann
(Fig. 114) was born at Frankfort-on-the-Main in 1834. He

4o6

BIOLOGY AND ITS MAKERS

was graduated at Gottingen in 1856, and for a short time
thereafter engaged in the practice of medicine. This hne of
activity did not, however, satisfy his nature, and he turned
to the pursuit of microscopic investigations in embryology

Fig. 114.— August Weismann, 1834- 19 14.

and morphology, being encouraged in this work by Leuckart,
whose name we have already met in this history. In 1863
he settled in Freiburg as privat-docent, and, in 1867, was
promoted to a professorship and taught in the department of

THEORIES OF WEISMANN AND DE VRIES 407

zoology, until his retirement a few years before his death.
He has made his department famous, especially by his lec-
tures on the theory of descent.

He was a forceful and interesting lecturer. One of his
hearers in 1896 wrote: "His lecture-room is always full, and
his popularity among his students fully equals his fame
among scientists."

It is quite generally known that Weismann since he reached
the age of thirty was afflicted with an eye-trouble, but the
inference sometimes made by those unacquainted with
his work as an investigator, that he was obliged to forego
practical work in the field in which he speculated, is wrong.
At intervals his eyes strengthened so that he was able to
apply himself to microscopic observations, and he has a
distinguished record as an observer. In embryology
his studies on the development of the diptera, and of
the eggs of daphnid Crustacea, are well known, as are also
his observations on variations in butterflies and other
arthropods.

He was an accomplished musician, and during the period
of his enforced inactivity in scientific work he found much
solace in playing "sl good deal of music." *'His continuous
eye trouble must have been a terrible obstacle, but may have
been the prime cause of turning him to the theories with
which his name is connected."

In a short autobiography published in The Lamp in 1903,
although written several years earlier, he gives a glimpse of
his family life. "During the ten years (1864-1874) of my
enforced inactivity and rest occurred my marriage with
Fraulein Marie Gruber, who became the mother of my
children and was my true companion for twenty years, until
her death. Of her now I think only with love and gratitude.
She was the one who, more than any one else, helped me
through the gloom of this period. She read much to me

4o8 BIOLOGY AND ITS MAKERS

at this time, for she read aloud excellently, and she not only
took an interest in my theoretical and experimental work,
but she also gave practical assistance in it."

In 1893 h^ published The Germ-Plasm, A Theory of
Heredity, a treatise which elicited much discussion. From
that time on he has been actively engaged in replying to his
critics and in perfecting his system of thought.

The Mutation-Theory of De Vries.— Hugo de Vries
(Fig. 115), director of the Botanical Garden in Amsterdam,
has experimented widely with plants, especially the evening
primrose (CEnothera Lamarckiana) , and has shown that dif-
ferent species appear to rise suddenly. The sudden variations
that breed true, and thus give rise to new forms, he calls mu-
tations, and this indicates the source of the name applied to
his theory.

In his i^i^ Mutationstheorie, published in 1901, he argues
for the recognition of mutations as the universal source of
the origin of species. Although he evokes natural selection
for the perpetuation and improvement of variations, and
points out that his theory is not antagonistic to that of natural
selection, it is nevertheless directly at variance with Darwin's
fundamental conception — that slight individual variations
" are probably the sole differences which are effective in the
production of new species" and that "as natural selection
acts solely by accumulating sUght, successive, favorable
variations, it can produce no great or sudden modifications."
The foundation of De Vries's theory is that "species have
not arisen through gradual selection, continued for hundreds
or thousands of years, but by jumps through sudden, through
small transformations." (Whitman's translation.)

The work of De Vries is a most important contribution
to the study of the origin of species, and is indicative of the
fact that many factors must be taken into consideration when
one attempts to analyze the process of organic evolution.
One great value of his work is that it is based on experiments,

THEORIES OF WEISMANN AND DE VRIES 409

and that it has given a great stimulus to experimental studies.
Experiment was likewise a dominant feature in Darwin's
work, but that seems to have been almost overlooked in
the discussions aroused by his conclusions; De Vries, by
building upon experimental evidence, has led naturalists to

Fig. 115. — Hugo de Vries.

realize that the method of evolution is not a subject for
argumentative discussion, but for experimental investigation.
This is most commendable.

De Vries's theory tends also to widen the field of explo-
ration. Davenport, Tower, and others have made it clear
that species may arise by slow accumulations of trivial varia-
tions, and that, while the formation of species by mutation

4IO BIOLOGY AND ITS MAKERS

may be admitted, there is still abundant evidence of evolu-
tion without mutation.

Reconciliation of Different Theories. — All this is leading
to a clearer appreciation of the points involved in the dis-
cussion of the theories of evolution; the tendency is not for
the breach between the different theories to be widened, but
for evolutionists to realize more fully the great complexity
of the process they are trying to explain, and to see that no
single factor can carry the burden of an explanation. Muta-
tion introduces a new factor of species-forming, but calls in
natural selection to improve the variations arising by muta-
tions. Weismann's suggestion of amphimixis, to explain the
origin of variations, and his extension of the principle of
selection to the germinal elements, is distinctly auxiliary to
the theory of natural selection and Lamarck's contribution
towards explaining the sources of variation is also supple-
mental. Thus we may look forward to a reconcihation be-
tween apparently conflicting views, and one conviction that
is looming into prominence is that this will be promoted by
less argument and more experimental observation.

That the solution of the underlying question in evolution
will still require a long time is evident; as Whitman said
in his address before the Congress of Arts and Science in
St. Louis in 1904: **The problem of problems in biology
to-day, the problem which promises to sweep through the
present century as it has the past one, with cumulative inter-
est and correspondingly important results, is the one which
became the life-work of Charles Darwin, and which can not
be better or more simply expressed than in the title of his
epoch-making book, The Origin oj Specie s.""

Summary. — The number of points involved in the four
theories considered above is likely to be rather confusing,

THEORIES OF WEISMANN AND DE VRIES 411

and we may now bring them into close juxtaposition. The
salient features of these theories are as follows:
I. Lamarck's Theory of Evolution.

1. Variation is explained on the principle of use and

disuse.

2. Heredity: The variations are inherited directly and

improved in succeeding generations.
A long time and favorable conditions are required
for the production of new species.
II. Darwin's Theory of Natural Selection.

1. Variations assumed.

2. Heredity: Those slight variations which are of use

to the organism will be perpetuated by inher-
itance.

3. Natural selection is the distinguishing feature of

the theory. Through the struggle for existence
nature selects those best fitted to survive. The
selection of trivial variations that are of advantage
to the organism, and their gradual improvement,
leads to the production of new species.
IIL Weismann's Theory of Continuity of the Germ-plasm.'

1. The germ-plasm has had unbroken continuity from

the beginning of life. Owing to its impression-
able nature, it has an inherited organization of
great complexity.

2. Heredity is accounted for on the principle that the

offspring is composed of some of the same stuff
as its parents. The body-cells are not inherited,
i.e.,

3. There is no inheritance of acquired characters.

4. Variations arise from the union of the germinal

elements, giving rise to varied combinations and
permutations of the qualities of the germ-plasm.
The purpose of amphimixis is to give rise to vari-

412 BIOLOGY AND ITS MAKERS

ations. The direct influence of environment has
produced variations in unicellular organism.
5. Weismann adopts and extends the principle of
natural selection. Germinal selection is exhibited
in the germ-plasm.
IV. De Vries's Theory of Mutations.

1. The formation of species is due not to gradual

changes, but to sudden mutations.

2. Natural selection presides over and improves varia-

tions arising from mutation.

From extended observations on the variabihty and the
adaptations of animals and plants, from the results of experi-
mental study and from intensive analysis of the various fac-
tors proposed to explain the process of species-forming, there
has resulted a remodeling of all evolutionary theories. New
theories have been advanced which, in their relation to Dar-
win's hypothesis of natural selection, fall into two categories.
There are competing theories designed to replace that of
natural selection; and there are auxihary, or supporting
theories, that are designed to throw new hght on the condi-
tions of species-forming and to strengthen the natural selec-
tion theory by its more complete elucidation. Such an ex-
tensive literature has grown up in the discussion of these
matters that, to cover it with any show of adequacy, re-
quires separate treatment, with specific illustrations and
extended comment. The entire case has been presented with
remarkable clearness in Kellogg's Darwinism To-day, and
since summaries of the arguments would be beyond the
purpose of this book, the reader is referred to Kellogg's
volume.

There are, however, two ideas of such fundamental im-
portance in the post-Darwinism discussions that they should

THEORIES OF WEISMANN AND DE VRIES 413

receive brief consideration here. These are designated re-
spectively, orthogenesis and isolation. Theodore Eimer is
the t}'pical representative of the ideas of orthogenesis. He
maintains that variations of organisms take place not for-
tuitously in radiating and heterogenous Hnes, but follow a
few definite directions. This definitely directed evolution
is called orthogenesis. He insists that there is continuous
inheritance of acquired characters, and he is radically op-
posed to the belief that natural selection plays an important
part in evolution. Variations are not preserved on the basis
of their utility, but as the result of the direct inheritance of
acquired characters. His theory was launched in 1888 (Or-
ganic Eovlution, 1889) ^ii^j ^s developed by Eimer, is to be
classed as a replacing theory. The title of his translated
pamphlet, published in English in 1898, On Orthogenesis and
the Impotence of Natural Selection in Species-Formation, is
suggestive as to his position in reference to natural selection.
Isolation as a favoring (or even indispensable) condition
of species-formation has been championed by Moritz Wagner
(since 1868), by David Starr Jordan, GuHck, Romanes, and
others. This is based on the assumption that isolation of
species has played an essential part in the perpetuation of
variations. Isolation is assumed to act upon variations after
they are started and not to play an important part in pro-
ducing variations. The basal question is, Under what condi-
tions will variations persist and become intensified? If free
intercrossings occur, it seems hkely that variations, which
at the beginning are slight, will tend to disappear. Accord-
ingly, it will be advantageous to have species living under
such conditions of segregation that those possessing similar
variations shall be compelled to breed together. This would
be accomplished by isolation of species either by geographical
barriers or by physiological infertiHty among two sections
of a species occupying the same territory. Romanes, who so

414 BIOLOGY AND ITS MAKERS

to speak, was Darwin's personal representative, regarded
isolation as an indispensable factor to the strengthening of
variations and thus bringing about the changes that lead to
the evolution of species.

The intensive scrutiny to which the different theories of
organic evolution have been subjected, has served to focahze
attention on various aspects of species forming. Natural
selection stands forth as the agency to direct the general
course of evolution after it is started, while as regards the be-
ginnings, there are other important questions as the causes
of variability, that await further investigation.

The cause for the general confusion in the popular mind
regarding any distinction between organic evolution and
Darwinism is not far to seek. As has been shown, Lamarck
launched the doctrine of organic evolution, but his views did
not even get a public hearing. Then, after a period of tem-
porary disappearance, the doctrine of evolution emerged
again in 1859. And this time the discussion of the general
theory centered around Darwin's hypothesis of natural selec-
tion. It is quite natural, therefore, that people should think
that Darwinism and organic evolution are synonymous terms.
The distinction between the general theory and any particular
explanation of it has, I trust, been made sufficiently clear in
the preceding pages.

CHAPTER XIX

THE RISE OF EVOLUTIONARY THOUGHT

A CURRENT of evolutionary thought can be traced through
the Uterature dealmg with organic nature from ancient times.
It began as a small rill among the Greek philosophers and
dwindles to a mere thread in the Middle Ages, sometimes
almost disappearing, but is never completely broken off.
Near the close of the eighteenth century it suddenly expands,
and becomes a broad and prevailing influence in the nine-
teenth century. Osborn, in his book. From the Greeks to
Darwin, traces the continuity of evolutionary thought from
the time of the Greek philosophers to Darwin. The ancient
phase, although interesting, was vague and general, and
may be dismissed without much consideration. After the
Renaissance naturalists were occupied with other aspects of
nature-study. They were at first attempting to get a knowl-
edge of animals and plants as a whole, and later of their
structure, their developments, and their physiology, before
questions of their origin were brought under consideration.

Opinion before Lamarck. — The period just prior to
Lamarck is of particular interest. Since Lamarck was the
first to give a comprehensive and consistent theory of evolu-
tion, it will be interesting to determine what was the state
of opinion just prior to the appearance of his writings.
Studies of nature were in such shape at that time that the
question of the origin of species arose, and thereafter it would
not recede. This was owing mainly to the fact that Ray and
Linnaeus by defining a species had fixed the attention of

415

4l6 BIOLOGY AND ITS MAKERS

naturalists upon the distinguishing features of the particular
kinds of animals and plants. Are species realities in nature ?
The consideration of this apparently simple question soon
led to divergent views, and then to warm controversies that
extended over several decades of time.

The view first adopted without much thought and as a
matter of course was that species are fixed and constant; i.e.,
that the existing forms of animals and plants are the descend-
ants of entirely similar parents that were originally created
in pairs. This idea of the fixity of species was elevated to the
position of a dogma in science as well as in theology. The
opposing view, that species are changeable, arose in the
minds of a few independent observers and thinkers, and, as
has already been pointed out, the discussion of this question
resulted ultimately in a complete change of view regarding
nature and man's relation to it. When the conception of
evolution came upon the scene, it was violently combated.
It came into conflict with the theory designated special
creation.

Views of Certain Fathers of the Church. — And now it is
essential that we should be clear as to the sources of this
dogma of special creation. It is perhaps natural to assume
that there was a conflict existing between natural science
and the views of the theologians from the earliest times;
that is, between the scientific method and the method of the
theologians, the latter being based on authority, and the
former upon observation and experiment. Although there
is a conflict between these two methods, there nevertheless
was a long period in which many of the leading theological
thinkers were in harmony with the men of science with refer-
ence to their general conclusions regarding creation. Some
of the early Fathers of the Church exhibited a broader and
more scientific spirit than their successors.

St. Augustine (353-430), in the fifth century, was the

RISE OF EVOLUTIONARY THOUGHT 417

first of the great theologians to discuss specifically the ques-
tion of creation. His position is an enlightened one. He
says: "It very often happens that there is some question as
to the earth or the sky, or the other elements of this world
. . . respecting which one who is not a Christian has knowl-
edge derived from most certain reasoning or observation"
(that is, a scientific man) ; " and it is very disgraceful and
mischievous and of all things to be carefully avoided, that a
Christian speaking of such matters as being according to the
Christian Scriptures, should be heard by an unbeliever talk-
ing such nonsense that the unbeliever, perceiving him to be
as wide from the mark as east from west, can hardly restrain
himself from laughing." (Quoted from Osborn.)

Augustine's view of the method of creation was that of
derivative creation or creation causaliter. His was a natural-
istic interpretation of the Mosaic record, and a theory of
gradual creation. He held that in the beginning the earth
and the waters of the earth were endowed with power to
produce plants and animals, and that it was not necessary to
assume that all creation was formed at once. He cautions
his readers against looking to the Scriptures for scientific
truths. He said in reference to the creation that the days
spoken of in the first chapter of Genesis could not be solar
days of twenty-four hours each, but that they must stand
for longer periods of time.

.This view of St. Augustine is interesting as being less
narrow and dogmatic than the position assumed by many
theologians of the nineteenth century.

The next theologian to take up the question of creation
was St. Thomas Aquinas (12 25-1 274) in the thirteenth cen-
tury. He quotes St. Augustine's view with approval, but
does not contribute anything of his own. One should not
hastily conclude, however, because these views were held by
leaders of theological thought, that they were universally

4i8 BIOLOGY AND ITS MAKERS

accepted. *'The truth is that all classes of theologians
departed from the original philosophical and scientific stand-
ards of some of the Fathers of the Church, and that special
creation became the universal teaching from the middle of
the sixteenth to the middle of the nineteenth centuries."

The Doctrine of Special Creation. — About the seven-
teenth century a change came about w^hich v^as largely owing
to the writings and influence of a Spanish theologian named
Suarez (1548-1617). Although Suarez is not the sole
founder of this conception, it is certain, as Huxley has shown,
that he engaged himself with the questions raised by the Bib-
lical account of creation; and, furthermore, that he opposed
the views that had been expressed by Augustine. In his
tract upon the work of the six days {Tractatus de opere sex
dierum) he takes exception to the views expressed by St.
Augustine; he insisted that in the Scriptural account of
creation a day of twenty-four hours was meant, and in all
other cases he insists upon a literal interpretation of the
Scriptures. Thus he introduced into theological thought the
doctrine which goes under the name of special creation.
The interesting feature in all this is that from the time of
St. Augustine, in the fifth century, to the time when the ideas
of Suarez began to prevail, in the seventeenth, there had been
a harmonious relation between some of the leading theolo-
gians and scientific men in their outlook upon creation.

The opinion of Augustine and other theologians was
largely owing to the influence of Aristotle. *'We know,"
says Osborn, " that Greek philosophy tinctured early Chris-
tian theology; what is not so generally realized is that the
Aristotelian notion of the development of life led to the true
interpretation of the Mosaic account of the creation.

"There was in fact a long Greek period in the history
of the evolutionary idea extending among the Fathers of the
Church and later among some of the schoolmen, in their

RISE OF EVOLUTIONARY THOUGHT 419

commentaries upon creation, which accord very closely with
the modern theistic conception of evolution. If the ortho-
doxy of Augustine had remained the teaching of the Church,
the final establishment of evolution would have come far
earlier than it did, certainly during the eighteenth century
instead of the nineteenth century, and the bitter controversy
over this truth of nature would never have arisen."

The conception of special creation brought into especial
prominence upon the Continent by Suarez was taken up by
John Milton in his great epic Paradise Lost, in which he
gave a picture of creation that molded into specific form
the opinion of the English-speaking clergy and of the
masses who read his book. When the doctrine of organic
evolution was announced, it came into conflict with this
particular idea; and, as Huxley has very pointedly remarked,
the new theory of organic evolution found itself in conflict
with the Miltonic, rather than the Mosaic cosmology. All this
represents an interesting phase in intellectual development.

Forerunners of Lamarck. — We now take up the imme-
diate predecessors of Lamarck. Those to be mentioned are
Buff on, Erasmus Darwin, and Goethe.

Buffon (1707-1788) (Fig. 116), although of a more philo-
sophical mind than many of his contemporaries, was not a
true investigator. That is, he left no technical papers or
contributions to science. From 1739 to the time of his death
he was the superintendent of the Jardin du Rot. He was a
man of elegance, with an assured position in society. He
was a delightful writer, a circumstance that enabled him to
make natural history popular. It is said that the advance
sheets of Buffon's Histoire Naturelle were to be found on the
tables of the boudoirs of ladies of fashion. In that work he
suggested the idea that the different forms of life were grad-
ually produced, but his timidity and his prudence led him
to be obscure in what he said.

420 BIOLOGY AND ITS MAKERS

Packard, who has studied his writings with care, says
that he was an evolutionist through all periods of his life, not,
as is commonly maintained, believing first in the fixity of
species, later in their changeability, and lastly returning to
his earUer position. ''The impression left on the mind after

Fig. ii6. — Buffon, 1707-1788.

reading Buffon is that even if he threw out these suggestions
and then retracted them, from fear of annoyance or even
persecution from the bigots of his time, he did not himself
always take them seriously, but rather jotted them down as
passing thoughts. Certainly he did not present them in the

RISE OF EVOLUTIONARY THOUGHT 421

formal, forcible, and scientific way that Erasmus Darwin did.
The result is that the tentative views of Buffon, which have
to be with much research extracted from the forty-four vol-
umes of his works, would now be regarded as in a degree
superficial and valueless. But they appeared thirty-four
years before Lamarck's theory, and though not epoch-making,

Fig. 117. — Erasmus Darwin, 1731-1802.

they are such as will render the name of Buffon memorable
for all time." (Packard.)

Erasmus Darwin (Fig. 117) was the greatest of Lamarck's
predecessors. In 1794 he pubhshed the Zoonomia. In this
work he stated ten principles; among them he vaguely
suggested the transmission of acquired characteristics, the
law of sexual selection — or the law of battle, as he called it —

422 BIOLOGY AND ITS MAKERS

protective coloration, etc. His work received some notice
from scholars. Paley's Natural Theology, for illustration,
was written against it, although Paley is careful not to men-
tion Darwin or his work. The success of Paley's book is
probably one of the chief causes for the neglect into which
the views of Buff on and Erasmus Darwin fell.

Inasmuch as Darwin's conclusions were published before
Lamarck's book, it would be interesting to determine whether
or not Lamarck was influenced by him. The careful con-
sideration of this matter leads to the conclusion that Lamarck
drew his inspiration directly from nature, and that points of
similarity between his views and those of Erasmus Darwin
are to be looked upon as an example of paralleUsm in
thought. It is altogether likely that Lamarck was wholly un-
acquainted with Darwin's work, which had been published
in England.

Goethe's connection with the rise of evolutionary thought
is in a measure incidental. In 1790 he published his Meta-
morphosis of Plants, showing that flowers are modified
leaves. This doctrine of metamorphosis of parts he presently
applied to the animal kingdom, and brought forward
his famous, but erroneous, vertebrate theory of the skull.
As he meditated on the extent of modifications there arose
in his mind the conviction that all plants and animals have
been evolved from the modification of a few parental types.
Accordingly he should be accorded a place in the history of
evolutionary thought.

Opposition to Lamarck's Views. — Lamarck's doctrine,
which was published in definite form in 1809, has been
already outlined. We may well inquire, Why did not his
views take hold ? In the first place, they were not accepted
by Cuvier. Cuvier's opposition was strong and vigorous,
and succeeded in causing the theory of Lamarck to be com-
pletely neglected by the French people. Again, we must

RISE OF EVOLUTIONARY THOUGHT 423

recognize that the time was not ripe for the acceptance of
such truths; and, finally, that there was no great principle
enunciated by Lamarck which could be readily understood
as there was in Darwin's book on the doctrine of natural
selection.

The temporary disappearance of the doctrine of organic
evolution which occurred after Lamarck expounded his theory
was also owing to the reaction against the speculations of
the school of Natur-Philosophie. The extravagant specula-
tion of Oken and the other representatives of this school
completely disgusted men who were engaged in research by
observation and experiment. The reaction against that
school was so strong that it was difficult to get a hearing for
any theoretical speculation; but Cuvier's influence must be
looked upon as the chief one in causing disregard for La-
marck's writings.

The work of Cuvier has been already considered in con-
nection both with comparative anatomy and zoology, but
a few points must still be held under consideration. Cuvier
brought forward the idea of catastrophism in order to explain
the disappearance of the groups of fossil animals. He be-
lieved in the doctrine of spontaneous generation. He held
to the doctrine of pre-delineation, so that it must be admitted
that whenever he forsook observation for speculation he
was singularly unhappy , and it is undeniable that his posi-
tion of hostility in reference to the speculation of Lamarck
retarded the progress of science for nearly half a century.

Cuvier and Saint-Hilaire.— In 1830 there occurred a
memorable controversy between Cuvier and Saint-Hilaire.
The latter (Fig. 118) was in early life closely associated with
Lamarck, and shared his views in reference to the origin of
animals and plants; though in certain points Saint-Hilaire
was more a follower of Buff on than of Lamarck. Strangely
enough, Saint-Hilaire was regarded as the stronger man of

424

BIOLOGY AND ITS MAKERS

the two. He was more in the pubUc eye, but was not a man
of such deep intellectuaUty as Lamarck. His scientific repu-
tation rests mainly upon his Philosophie Anatomique. The
controversy between him and Cuvier was on the subject of

Fig. ii8. — Geoffroy Saint-Hilaire, 1772-1844.

unity of type; but it involved the question of the fixity or
mutability of species, and therefore it involved the foundation
of the question of organic evolution.

This debate stirred all intellectual Europe. Cuvier won
as being the better debater and the better manager of his

I

RISE OF EVOLUTIONARY THOUGHT 425

case. He pointed triumphantly to the four branches of the
animal kingdom which he had established, maintaining that
these four branches represented four distinct types of organi-
zation ; and, furthermore, that fixity of species and fixity of
type were necessary for the existence of a scientific natural
history. We can see now that his contention was wrong,
but at the time he won the debate. The young men of
the period, that is, the rising biologists of France, were
nearly all adherents of Cuvier, so that the effect of the de-
bate was, as previously stated, to retard the progress of sci-
ence. This noteworthy debate occurred in February, 1830.
The wide and lively interest with which the debate was
followed may be inferred from the excitement manifested
by Goethe. Of the great poet-naturalist, who was then in
his eighty-first year, the following incident is told by Soret :

"Monday, Aug. 2d, 1830. — ^The news of the outbreak of
the revolution of July arrived in Weimar to-day, and has
caused general excitement. In the course of the afternoon
I went to Goethe. ' Well,' he exclaimed as I entered, * what
do you think of this great event ? The volcano has burst
forth, all is in flames, and there are no more negotiations
behind closed doors.' *A dreadful affair,' I answered;
*but what else could be expected under the circumstances,
and with such a ministry, except that it would end in the
expulsion of the present royal family?' *We do not seem
to understand each other, my dear friend,' replied Goethe.
*I am not speaking of those people at all; I am interested
in something very different. I mean the dispute between
Cuvier and Geoffroy de Saint-Hilaire, which has broken out
in the Academy, and which is of such great importance to
science.' This remark of Goethe came upon me so unex-
pectedly that I did not know what to say, and my thoughts
for some minutes seemed to have come to a- complete stand-
still. *The affair is of the utmost importance,' he con-

426 BIOLOGY AND ITS MAKERS

tinued, 'and you can not form any idea of what I felt on
receiving the news of the meeting on the 19th. In Geoffroy
de Saint-Hilaire we have now a mighty ally for a long time
to come. But I see also how great the sympathy of the
French scientific world must be in this affair, for, in spite of
the terrible political excitement, the meeting on the 19th
was attended by a full house. The best of it is, however,
that the synthetic treatment of nature, introduced into
France by Geoffroy, can now no longer be stopped. This
matter has now become public through the discussions in the
Academy, carried on in the presence of a large audience;
it can no longer be referred to secret committees, or be settled
or suppressed behind closed doors.' "

Influence of LyelPs Principles of Geology. — But just as
Cuvier was triumphing over Saint-Hilaire a work was being
published in England which was destined to overthrow the
position of Cuvier and to bring again a sufficient foundation
for the basis of mutability of species. I refer to Lycll's
Principles of Geology, the influence of which has already
been spoken of in Chapter XV. Lyell laid down the prin-
ciple that we are to interpret occurrences in the past in the
terms of what is occurring in the present. He demonstrated
that observations upon the present show that the surface of
the earth is undergoing gradually slow changes through the
action of various agents, and he pointed out that we must
view the occurrences in the past in the light of occurrences
in the present. Once this was applied to animal forms it
became evident that the observations upon animals and plants
in the present must be applied to the life of the fossil series.

These ideas, then, paved the way for the conception of
changes in nature as being one continuous series.

H. Spencer. — In 1852 came the publication of Herbert
Spencer in the Leader, in which he came very near antici-
pating the doctrine of natural selection. He advanced the

RISE OF EVOLUTIONARY THOUGHT 427

developmental hypothesis, saying that even if its supporters
could ^'merely show that the production of species by the
process of modification is conceivable, they would be in a
better position than their opponents. But they can do much
more than this ; they can show that the process of modifica-
tion has affected and is affecting great changes in all organ-
isms subject to modifying influences. . . . They can show
that any existing species, animal or vegetable, when placed
under conditions different from its previous ones, imme-
diately begins to undergo certain changes of structure fitting
it for the new conditions. They can show that in successive
generations these changes continue, until ultimately the
new conditions become the natural ones. They can show
that in cultivated plants and domesticated animals, and in the
several races of men, these changes have uniformly taken
place. They can show that the degrees of difference so pro-
duced are often, as in dogs, greater than those on which dis-
tinctions of species are in other cases founded. They can show
that it is a matter of dispute whether some of these modified
forms are varieties or modified species. And thus they can
show that throughout all organic nature there is at work a
modifying influence of the kind they assign as the cause of
these specific differences; an influence which, though slow
in its action, does in time, if the circumstances demand it,
produce marked changes; an influence which, to all appear-
ance, would produce in the millions of years, and under the
great varieties of conditions which geological records imply,
any amount of change."

"It is impossible," says Marshall, "to depict better than
this the condition prior to Darwin. In this essay there is full
recognition of the fact of transition, and of its being due to
natural influences or causes, acting now and at all times.
Yet it remained comparatively unnoticed, because Spencer,
like his contemporaries and predecessors, while advocating

428 BIOLOGY AND ITS MAKERS

evolution, was unable to state explicitly what these causes
were."

Darwin and Wallace. — In 1858 we come to the crown-
ing event in the rise of evolutionary thought, when Alfred
Russel Wallace sent a communication to Mr. Darwin, beg-
ging him to look it over and give him his opinion of it. Darwin,
who had been working upon his theory for more than twenty
years, patiently gathering facts and testing the same by
experiment, was greatly surprised to find that Mr. Wallace
had independently hit upon the same principle of explaining
the formation of species. In his generosity, he was at first
disposed to withdraw from the field and publish the essay of
Wallace without saying anything about his own work. He
decided, however, to abide by the decision of two of his
friends, to whom he had submitted the matter, and the result
was that the paper of Wallace, accompanied by earlier com-
munications of Darwin, were laid before the Linnaean Society
of London. This was such an important event in the his-
tory of science that its consideration is extended by quoting
the following letter:

"London, June 30th, 1858.

"My Dear Sir: The accompanying papers, which we
have the honor of communicating to the Linnaean Society,
and which all relate to the same subject; viz., the laws which
affect the production of varieties, races, and species, contain
the results of the investigations of two indefatigable natural-
ists, Mr. Charles Darwin and Mr. Alfred Wallace.

"These gentlemen having, independently and unknown
to one another, conceived the same very ingenious theory to
account for the appearance and perpetuation of varieties
and of specific forms on our planet, may both fairly claim the
merit of being original thinkers in this important line of
inquiry; but neither of them having published his views.

I

RISE OF EVOLUTIONARY THOUGHT 429

though Mr. Darwin has for many years past been repeatedly
urged by us to do so, and both authors having now unreserv-
edly placed their papers in our hands, we think it would
best promote the interests of science that a selection from
them should be laid before the Linnaean Society.

"Taken in the order of their dates, they consist of:

" I. Extracts from a MS. work on species, by Mr. Dar-
win, which was sketched in 1839 and copied in 1844, when
the copy was read by Dr. Hooker, and its contents afterward
communicated to Sir Charles Lyell. The first part is devoted
to The Variation of Organic Beings under DomesticaHon and
in their Natural State; and the second chapter of that part,
from which we propose to read to the Society the extracts
referred to, is headed On the Variation of Organic Beings in
a State of Nature ; on the Natural Means of Selection; on the
Comparison of Domestic Races and True Species.

"2. An abstract of a private letter addressed to Professor
Asa Gray, of Boston, U. S., in October, 1857, by Mr. Darwin,
in which he repeats his views, and which shows that these
remained unaltered from 1839 to 1857.

"3. An essay by Mr. Wallace, entitled On the Tendency
of Varieties to Depart Indefinitely from the Original Type,
This was written at Ternate in February, 1858, for the
perusal of his friend and correspondent, Mr. Darwin, and
sent to him with the expressed wish that it should be for-
warded to Sir Charles Lyell, if Mr. Darwin thought it suffi-
ciently novel and interesting. So highly did Mr. Darwin
appreciate the value of the views therein set forth that he
proposed, in a letter to Sir Charles Lyell, to obtain Mr.
Wallace's consent to allow the essay to be pubHshed as soon
as possible. Of this step we highly approved, provided Mr.
Darwin did not withhold from the public, as he was strongly
inclined to do (in favor of Mr. Wallace), the memoir which
he had himself written on the same subject, and which, as

I

430 BIOLOGY AND ITS MAKERS

before stated, one of us had perused in 1844, and the con-
tents of which we had both of us been privy to for many years.

'^ On representing this to Mr. Darwin, he gave us permis-
sion to make what use we thought proper of his memoir, etc. ;
and in adopting our present course, of presenting it to the
Linnaean Society, we have explained to him that we are not
solely considering the relative claims to priority of himself
and his friend, but the interests of science generally; for we
feel it to be desirable that views founded on a wide deduction
from facts, and matured by years of reflecting, should con-
stitute at once a goal from which others may start ; and that,
while the scientific world is waiting for the appearance of
Mr. Darwin's complete work, some of the leading results of
his labours, as well as those of his able correspondent, should
together be laid before the pubHc.

''We have the honour to be yours very obediently,

Charles Lyell,
Jos. D. Hooker."

Personality of Darwin. — The personality of Darwin is
extremely interesting. Of his numerous portraits, the one
shovel in Fig. 119 is less commonly known than those show-
ing him with a beard and a much furrowed forehead. This
portrait represents him in middle life, about the time of the
publication of his Origin of Species. It shows a rather
typical British face, of marked individuality. Steadiness,
sincerity, and urbanity are all depicted here. His bluish-
gray eyes were overshadowed by a projecting ridge and very
prominent, bushy eyebrows that make his portrait, once seen,
easily recognized thereafter. In the full-length portraits
representing him seated, every line in his body shows the quiet,
philosophical temper for which he was notable. An intimate
account of his life is contained in the Life and Letters 0)
Charles Darwin (1887) and in More Letters oj Darwin^igoT,),

RISE OF EVOLUTIONARY THOUGHT 431

both of which are illustrated by portraits and other pictures.
The books about Darwin and his work are numerous, but
the reader is referred in particular to the two mentioned as
giving the best conception of the great naturalist and of his
personal characteristics.

He is described as being about six feet high, but with a
stoop of the shoulders which diminished his apparent height;

Fig. 119. — Charles Darwin, 1809-1882,

"of active habits, but with no natural grace or neatness of
movement." *'In manner he was bright, animated, and
cheerful; a delightfully considerate host, a man of never-
failing courtesy, leading him to reply at length to letters
from anybody, and sometimes of a most foolish kind.'^

His Home Life. — " Darwin was a man greatly loved and
respected by all who knew him. There was a peculiar charm

432 BIOLOGY AND ITS MAKERS

about his manner, a constant deference to others, and a
faculty for seeing the best side of everything and every-
body."

He was most affectionate and considerate at home. The
picture of Darwin's hfe with his children gives a glimpse
of the tenderness and deep affection of his nature, and the
reverent regard with which he was held in the family circle
is very touching. One of his daughters writes: ''My first
remembrances of my father are of the delights of his playing
with us. He was passionately attached to his own children,
although he was not an indiscriminate child-lover. To all
of us he was the most delightful playfellow, and the most
perfect sympathizer. Indeed, it is impossible adequately to
describe how delightful a relation his was to his family,
whether as children or in their later life.

"It is a proof of the terms on which we were, and also of
how much he was valued as a playfellow, that one of his sons,
when about four years old, tried to bribe him with a sixpence
to come and play in working hours. We all knew the sacred-
ness of working time, but that any one should resist sixpence
seemed an impossibility."

Method of Work. — Darwin's Ufe, as might be inferred
from the enduring quality of his researches, shows an
unswerving purpose. His theory was not the result of a
sudden flash of insight, nor was it struck out in the heat
of inspiration, but was the product of almost unexampled
industry and conscientious endeavor in the face of unfavor-
able circumstances. Although strikingly original and inde-
pendent as a thinker, he was slow to arrive at conclusions,
examining with the most minute and scrupulous care the
ground for every conclusion. "One quality of mind that
seemed to be of especial advantage in leading him to make
discoveries was the habit of never letting exceptions pass
unnoticed." He enjoyed experimenting much more than

RISE OF EVOLUTIONARY THOUGHT 433

work which only entailed reasoning. Of course, he was a
great reader, but for books as books he had no respect, often
cutting large ones in two in order to make them easier to
hold while in use.

Darwin^s Early Life. — Charles Darwin was born in 1809
at Shrewsbury, England, of distinguished ancestry, his grand-
father being the famous Dr. Erasmus Darwin, the founder,
as we have seen, of a theory of evolution. In his youth he
gave no indication of future greatness. He was sent to
Edinburgh to study medicine, but that the work |ailed to
arouse in him an absorbing interest is shown by his charac-
terizing some of the lectures as " incredibly dull." After two
sessions, at the suggestion of his father, he left Edinburgh to
study for the Church. He then entered Christ's College,
Cambridge, where he remained for three years. After ta-
king his baccalaureate degree at Cambridge, where he had
manifested an interest in scientific study, and had been
encouraged by Professor Henslow, came the event which
proved, as Darwin says, ''the turning-point of my life."
This was his appointment as naturalist on the surveying
expedition about to be entered upon by the ship Beagle.
An amusing circumstance connected with his appointment
is that he was nearly rejected by Captain Fitz-Roy, who
doubted "whether a man with such a shaped nose could
possess sufficient energy and determination for the voyage."

Voyage of the Beagle. — The voyage of the Beagle ex-
tended over five years (1831-1836), mainly along the west
coast of South America. It was on this- voyage that Darwin
acquired the habit of constant industry. He had also oppor-
tunity to take long trips on shore, engaged in observation
and in making extensive collections. He observed nature in
the field under exceptional circumstances. As he traveled
he noted fossil forms in rocks as well as the living forms in
field and forest. He observed the correspondence in type

>

434 BIOLOGY AND ITS MAKERS

between certain extinct forms and recent animals in South
America. He noticed in the Galapagos Islands a fauna similar
in general characteristics to that of the mainland, five or six
hundred miles distant, and yet totally different as to species.
Moreover, certain species were found to be confined to par-
ticular islands. These observations awakened in his mind,
a mind naturally given to inquiring into the causes of things,
questions that led to the formulation of his theory. It was
not, however, until 1837 that he commenced his first note-
book for containing his observations upon the transmutations
of animals. He started as a firm believer in the fixity of
species, and spent several years collecting and considering
data before he changed his views.

At Down. — On his return to England, after spending
some time in London, he purchased a country-place at Down
and, as his inheritance made it possible, he devoted himself
entirely to his researches.

But, as is well known, he found in his illness a great
obstacle to steady work. He had been a vigorous youth and
young man, fond of outdoor sports, as fishing, shooting,
and the like. After returning from his long voyage, he was
affected by a form of constant illness, involving a giddiness
in the head, and "for nearly forty years he never knew one
day of the health of an ordinary man, and thus his life was
one long struggle against the weariness and strain of sick-
ness." Gould in his Biographical Clinics attributes his ill-
ness to eye- strain.

" Under such conditions absolute regularity of routine was
essential, and the day's work was carefully planned out. At
his best, he had three periods of work: from 8.00 to 9.30;
from 10.30 to 12.15; ^^^ irova 4.30 to 6.00, each period being
under two hours' duration."

The patient thoroughness of his experimental work and of
his observation is shown by the fact that he did not publish

RISE OF EVOLUTIONARY THOUGHT 435

his book on the Origin oj Species until he had worked on
his theory twenty-two years. The circumstances that led
to his publishing it when he did have already been indi-
cated.

Parallelism in the Thought of Darwin and Wallace. —
No one can read the letters of Darwin and Wallace explaining
how they arrived at their idea of natural selection without
marveling at the remarkable parallelism in the thought of the
two. It is a noteworthy circumstance that the idea of natural
selection came to both by the reading of the same book, Mal-
ihus on Population,

Darwin's statement of how he arrived at the concep-
tion of natural selection is as follows: "In October, 1838,
that is, fifteen months after I had begun my systematic
inquiry, I happened to read for amusement Malthus on
Population, and being well prepared to appreciate the
struggle for existence which everywhere goes on from long-
continued observations of the habits of animals and plants,
it at once struck me that under these circumstances favourable
variations would tend to be preserved and unfavourable ones
to be destroyed. The result oj this would he the formation
of new species. Here then I had at last got a theory by
which to work, but I was so anxious to avoid prejudice that
I determined not for some time to write even the briefest
sketch of it. In June, 1842, I first allowed myself the satis-
faction of writing a very brief abstract of my theory in pencil,
in thirty-five pages, and this was enlarged during the summer
of 1844 into one of 230 pages."

And Wallace gives this account: "In February, 1858, I
was suffering from a rather severe attack of intermittent fever
at Temate, in the Moluccas; and one day, while lying on
my bed during the cold fit, wrapped in blankets, though the
thermometer was at ^^° Fahr., the problem again presented
itself to me, and something led me to think of the 'positive

436

BIOLOGY AND ITS MAKERS

checks' described by Malthus in his Essay on Population ,
a work I had read several years before, and which had made
a deep and permanent impression on my mind. These
checks — war, disease, famine, and the Hke — must, it occurred
to me, act on animals as well as man. Then I thought of

Fig. 1 20. — Alfred Russel Wallace, 1823-1913.

the enormously rapid multiplication of animals, causing these
checks to be much more effective in them than in the case of
man; and while pondering vaguely on this fact, there sud-
denly flashed upon me the idea of the survival of the fittest —
that the individuals removed by these checks must be on the

RISE OF EVOLUTIONARY THOUGHT 437

whole inferior to those that survived. In the two hours that
elapsed before my ague fit was over, I had thought out
almost the whole of the theory; and the same evening I
sketched the draught of my paper, and in the two succeeding
evenings wrote it out in full, and sent it by the next post to
Mr. Darwin."

It thus appears that the announcement of the Darwin-
Wallace theory of natural selection was made in 1858, and
in the following year was published the book, the famous
Origin oj Species, upon which Darwin had been working
when he received Mr. Wallace's essay. Darwin spoke of this
work as an outline, a sort of introduction to other works
that were in the course of preparation. His subsequent
works upon Animals and Plants under Domestication, The
Descent oj Man, etc., etc., expanded his theory, but none of
them effected so much stir in the intellectual world as the
Origin oj Species.

This skeleton outline should be filled out by reading
Darwin^ s Lije and Letters, by his son, and the complete
papers of Darwin and Wallace, as originally published in
the Journal oj the Linncean Society. The original papers
are reproduced in the Popular Science Monthly for Novem-
ber, 1 90 1.

Wallace was born in 1823, and died Nov. 7, 1913. He
shares with Darwin the credit of propounding the theory of
natural selection, and he is notable also for the publication of
important books, as the Malay Archipelago, The Geographical
Distribution of Animals, The Wonderful Century, etc.

The Spread of the Doctrine of Organic Evolution. Hux-
ley.— Darwin was of a quiet habit, not aggressive in the
defense of his views. His theory provoked so much oppo-
sition that it needed some defenders of the pugnacious type,
^fc In England such a man was found in Thomas Henry Huxley
^H (1825-1895). He was one of the greatest popular exponents

L

438

BIOLOGY AND ITS MAKERS

of science of the nineteenth century; a man of most thorough
and exact scholarship, with a keen, analytical mind that went
directly to the center of questions under consideration, and
powers as a writer that gave him a wide circle of readers.
He was magnificently sincere in his fight for the prevalence

Fig. 121. — Thomas Henry Huxley, 1825-1895.

of intellectual honesty. Doubtless he will be longer remem-
bered for this service than for anything else.

He defended the doctrine of evolution, not only against
oratorical attacks like that of Bishop Wilberforce, but against
well-considered arguments and more worthy opponents. He
advanced the standing of the theory in a less direct w^ay
by urging the pursuit of scientific studies by high-school
and university students, and by bringing science closer to

RISE OF EVOLUTIONARY THOUGHT 439

the people. He was a pioneer in the laboratory teaching of
biology, and his Manual has been, ever since its publica-
tion in 1874, the inspiration and the model for writers of
directions for practical work in that field.

It is not so generally known that he was also a great
investigator, producing a large amount of purely technical
researches. After his death a memorial edition of his scien-
tific memoirs was published in four large quarto volumes.
The extent of his scientific output when thus assembled was
a surprise to many of his co-workers in the field of science.
His other writings of a more general character have been
collected in fourteen volumes. Some of the essays in
this collection are models of clear and vigorous English
style. Mr. Huxley did an astonishing amount of scientific
work, especially in morphology and palaeontology. Those
who have been privileged to look over his manuscripts and
unpublished drawings in his old room at South Kensington
could not fail to have been impressed, not only with the
extent, but also with the accuracy of his work. Taking
Johannes Miiller as his exemplar, he investigated animal
organisms with a completeness and an exactness that have
rarely been equaled.

An intimate account of his life will be found in The Life
and Letters oj Thomas Henry LLuxley, by his son.

Haeckel. — Ernst Haeckel, of Jena, bom in 1834 (Fig. 122),
was one of the earliest in Germany to take up the de-
fense of Darwin's hypothesis. As early as 1866 he applied
the doctrine of evolution to all organisms in his Generelle
Morphologie. This work, which has been long out of print,
represents his best contribution to evolutionary thought.
He has written widely for general readers, and although his
writings are popularly believed to represent the best scientific
thought on the matter, those written for the general public
are not regarded by most biologists as strictly representative.

440

BIOLOGY AND ITS MAKERS

As a thinker he is more careless than Huxley, and as a result
less critical and exact as a writer.

There can be no doubt that the germs of evolutionary
thought existed in Greek philosophy, and that they were

Fig. 122. — Ernst Haeckel, Born 1834.

retained in a state of low vitality among the mediaeval thinkers
who reflected upon the problem of creation. It was not,
however, until the beginning of the nineteenth century that,
under the nurture of Lamarck, they grew into what we may
speak of as the modern theory of evolution. After various
vicissitudes this doctrine was made fertile by Darwin, who
supplied it with a new principle, that of natural selection.

The fruits of this long growth are now being gathered.
After Darwin the problem of biology became not merely
to describe phenomena, but to explain them. This is the

RISE OF EVOLUTIONARY THOUGHT 441

outcome of the rise and progress of biology : first, crude and
uncritical observations of the forms of animated nature;
then descriptive analysis of their structure and development;
and, finally, experimental studies, the effort to explain vital
phenomena, an effort in which biologists are at present en-
gaged.

CHAPTER XX

RETROSPECT AND PROSPECT. RECENT TENDEN
CIES IN BIOLOGY

When one views the progress of biology in retrospect, the
broad truth stands out that there has been a continuity of
development in biological thought and interpretation. The
new proceeds out of the old, but is genetically related to it.
A good illustration of this is seen in the modified sense in
which the theories of epigenesis and pre-formation have been
retained in the biological philosophy of the nineteenth cen-
tury. The same kind of question that divided the philos-
ophers of the seventeenth and eighteenth centuries has
remained to vex those of the nineteenth; and, although both
processes have assumed a different aspect in the light of ger-
minal continuity, the theorists of the last part of the nineteenth
century were divided in their outlook upon biological proc-
esses into those of the epigenetic school and those who are
persuaded of a pre-organization in the germinal elements of
organisms. Leading biological questions were warmly dis-
cussed from these different points of view.

In its general character the progress of natural science
has been, and still is, a crusade against superstition; and it
may be remarked in passing that '' the nature of superstition
consists in a gross misunderstanding of the causes of nat-
ural phenomena." The struggle has been more marked in
biology than in other departments of science because biology
involves the consideration of living organisms and undertakes

442

RECENT TENDENCIES IN BIOLOGY 443

to establish the same basis for thinking about the organization
of the human body as about the rest of the animal series.

The first triumph of the scientific method was the over-
throw of authority as a means of ascertaining truth and sub-
stituting therefor the method of observation and experiment.
This carries us back to the days of Vesalius and Harvey,
before the framework of biology was reared. But the scien-
tific method, once established, led on gradually to a belief in
the constancy of nature and in the prevalence of universal
laws in the production of all phenomena. In its progress
biology has exhibited three phases which more or less
overlap: The first was the descriptive phase, in which
the obvious features of animals and plants were merely
described; the descriptive was supplemented by the com-
parative method; this in due course by the experimental
method, or the study of the processes that take place in
organisms. Thus, description, comparison, and experiment
represent the great phases of biological development.

The Notable Books of Biology and their Authors.— The
progress of biology has been owing to the efforts of men of
very human qualities, yet each with some special distinguish-
ing feature of eminence. Certain of their publications are
the mile-stones of the way. It may be worth while, therefore,
in a brief recapitulation to name the books of widest general
influence in the progress of biology. Only those publica-
tions will be mentioned that have formed the starting-point
of some new movement, or have laid the foundation of some
new theory.

Beginning with the revival of learning, the books of
Vesalius, De Corporis Humani Fabrica (1543), and Harvey,
De Motii Cordis et Sanguinis (1628), laid the foundations of
scientific method in biology.

The pioneer researches of Malpighi on the minute anat-
omy of plants and animals, and on the development of the

444 BIOLOGY AND ITS MAKERS

chick, best represent the progress of investigation between
Harvey and Linnaeus. The three contributions referred to
are those on the Anatomy of Plants {Anatome Plantarum,
1675-1679); on the Anatomy of the Silkworm {De Bomhyce^
1669) ; and on the Development oj the Chick {De Formatione
Pulli in Ovo and De Ovo Incubato, both 1672).

We then pass to the Systema Naturce (twelve editions,
1 735-1 768) of Linnaeus, a work that had such wide in-
fluence in stimulating activity in systematic botany and
zoology.

Wolff's Theoria Generationis, 1759, and his De Formatiofie
Intestinorumy 1764, especially the latter, were pieces of
observation marking the highest level of investigation of
development prior to that of Pander and Von Baer.

Cuvier, in Le Rbgne Animal ^ 18 16, applied the principles
of comparative anatomy to the entire animal kingdom.

The publication in 1800 of Bichat's Traite des Membraftes
created a new department of anatomy, called histology.

Lamarck's book. La Philosophie Zoologique, 1809, must
have a place among the great works in biology. Its influence
was delayed for more than fifty years after its publication.

The monumental work of Von Baer on Development
{Ueber Entwicklungsgeschichie der Thiere), 1828, is an almost
ideal combination of observation and conclusion in embry-
ology.

The Microscopische Untersuchungen, 1839, of Schwann
marks the foundation of the cell-theory.

The Handbook of Johannes Muller {Handbuch der
Physiologie des Menschen), 1846, remains unsurpassed as to
its plan and its execution.

Max Schultze in his treatise Ueber Muskelkorperchen und
das was man eine Zelle zu nennen habe, 186 1, established one
of the most important conceptions with which biology has
been enriched, viz., the protoplasm doctrine. '

RECENT TENDENCIES IN BIOLOGY 445

Darwin's Origin of Species, 1859, is, from our present
outlook, the greatest classic in biology.

Pasteur's Studies on Fermentation, 1876, is typical of the
quality of his work, though his later investigations on in-
oculations for the prevention of hydrophobia and other
maladies are of greater importance to mankind.

Ii is somewhat puzzling to select a man to represent the
study of fossil life, one is tempted to name E. D. Cope,
whose researches were conceived on the highest plane.
Zittel, however, covered the entire field of fossil life, and his
Handbook of Palceontology is designated as a mile-post in the
development of that science.

Before the Renaissance the works of Aristotle and Galen
should be included.

From the view-point suggested, the more notable figures in
the development of biology are: Aristotle, Galen, Vesalius,
Harvey, Malpighi, Linnaeus, Wolff, Cuvier, Bichat, Lamarck,
Von Baer, J. Miiller, Schwann^ Schultze, Darwin, Pasteur,
and Zittel.

Such a list is, as a matter of course, arbitrary, and can
serve no useful purpose except that of bringing into com-
bination in a single group the names of the most illustrious
founders of biological science. The individuals mentioned
are not all of the same relative rank, and the list should be
extended rather than contracted. Schwann, when the entire
output of the two is considered, would rank lower as a scien-
tific man than Koelliker, who is not mentioned, but the
former must stand in the list on account of his connection
with the cell-theory. Virchow, the presumptive founder of
pathology, is omitted, as are also investigators like Koch,
whose line of activity has been chiefly medical.

Recent Tendencies in Biology. Higher Standards. — In
attempting to indicate some of the more evident influences
that dominate biological investigation at the present time;,

446 BIOLOGY AND ITS MAKERS

nothing more than an enumeration of tendencies with a
running commentary is possible. One notes first a whole-
some influence in the establishment of higher standards, both
of research and of scientific publication. Investigations as a
whole have become more intensive and more critical. Much
of the work that would have passed muster for publication
two decades ago is now regarded by the editors of the best
biological periodicals as too general and too superficial. The
requisites for the recognition of creditable work being higher,
tends to elevate the whole level of biological science.

Improvement in Tools and Methods. — This has come
about partly through improvement in the tools and in the
methods of the investigators. It can hardly be said, however,
that thinking and discernment have been advanced at the
same rate as the mechanical helps to research. In becoming
more intensive, the investigation of biological problems has
lost something in comprehensiveness. That which some of
the earlier investigators lacked in technique was compensated
for in the breadth of their preliminary training and in their
splendid appreciation of the relations of the facts at their
disposal.

The great improvement in the mechanical adjustments
and in the optical powers of microscopes has made it possible
to see more regarding the physical structure and the activities
of organisms than ever before. Microtomes of the best work-
manship have placed in the hands of histologists the means
of making serial sections of remarkable thmness and regular-
ity.

The great development of micro-chemical technique also
has had the widest influence in promoting exact researches
in biology. Special staining methods, as those of Golgi
and Bethe, by means of which the wonderful fabric of the
nervous system has been revealed, are illustrations.

The separation by maceration and smear preparation of en-

RECENT TENDENCIES IN BIOLOGY 447

tire histological elements so that they may be viewed as solids
has come to supplement the study of sections. Reconstruc-
tion, by carving wax plates of known thickness into the form
of magnified sections drawn upon their surfaces to a scale,
and then fitting the plates together, has been very helpful in
picturing complicated anatomical relations. This method
has made it possible to produce permanent vv^ax models of
minute structures magnified to any desired degree. Minute
dissections, although not yet sufficiently practiced, are never-
theless better than the wax models for making accurate
drawings of minute structures as seen in relief.

The injection of the blood-vessels of extremely small
embryos has made it possible to study advantageously the
circulatory system. The softening of bones by acid after
the tissues are already embedded in celloidin has offered a
means of investigating the structure of the internal ear by
sections, and is widely applicable to other tissues.

With the advantage of the new appliances and the new
methods, the old problems of anatomy are being worked over
on a higher level of requirement. Still, it is doubtful whether
even the old problems will be solved in more than a relative
way. It is characteristic of the progress of research that as
one proceeds the horizon broadens and new questions spring
up in the pathway of the investigator. He does not solve
the problems he sets out to solve, but opens a lot of new ones.
This is one of the features of scientific research that make
its votaries characteristically optimistic.

Experimental Work. — Among the recent influences tend-
ing to advance biology, none is more important than the ap-
plication of experiments to biological studies. The exper-
imental method is in reahty applicable to diverse fields of
biological research, and its extensive use at present indicates
a movement in the right direction ; that is, a growing interest
in the study of processes. One of the earliest problems of

448 BIOLOGY AND ITS MAKERS

the biologist is to investigate the architecture of Hving beings;
then there arise questions as to the processes that occur within
the organism, and the study of processes involves the employ-
ment of experiments. In the pursuit of physiology exper-
iments have been in use since the time of Harvey, but even
in that science, v^here they are indispensable, experiments
did not become comparative until the nineteenth century.
It now appears that various forms of experiment give also
a better insight into the structure of organisms, and the prac-
tice of applying experiments to structural studies has given
rise to the new department of experimental morphology.

For the purpose of indicating some of the directions in
which biology has been furthered by the experimental method
of investigation, we designate the fields of heredity and evo-
lution, changes in the environment of organisms, studies on
fertilization and on animal behavior.

The recognition that both heredity and the process of
evolution can be subjected to experimental tests was a revela-
tion. Darwin and the early evolutionists thought the evolu-
tionary changes too slow to be appreciated, but now we
know that many of the changes can be investigated by
experiment. Numerous experiments on heredity in poultry
(Davenport), in rats, in rabbits, and in guinea-pigs (Castle)
have been carried out — experiments that test the laws of
ancestral inheritance and throw great light upon the ques-
tions introduced by the investigations of Mendel and De
Vries. The investigations of De Vries on the evolution of
plant-life occupy a notable position among the experimental
studies.

A large number of experiments on the effects produced
by changes in the external conditions of life have been made.
To this class of investigations belong studies on the regulation
of form and function in organisms (Loeb, Child), the effects
produced by altering mechanical conditions of growth, by

RECENT TENDENCIES IN BIOLOGY 449

changing the chemical environment, etc. There is some
internal mechanism in living matter that is influenced by
changes in external conditions, and the study of the regulation
of the internal processes that produce form and structure
have given rise to a variety of interesting problems. The
regeneration of lost parts and regeneration after intention-
ally-imposed injury has received much attention (Morgan).
Marine animals are especially amenable to manipulations of
this nature, as well as to alterations in their surroundings,
on account of the ease in altering the chemical environment
in which they live. The latter may be accomplished by
dissolving harmless chemical salts in the sea-water, and
observing the changes produced by the alterations of the
surrounding conditions. By this means Herbst and others
have produced very interesting results.

In the field of artificial fertilization, free swimming larvae
have been raised from eggs artificially fertilized by changes
in osmotic pressure, and also by treating them with both
organic and inorganic acids; and these studies have greatly
altered opinion regarding the nature of fertilization, and of
certain other phenomena of development.

Animal Behavior. — The study of animal behavior (Jen-
nings) is a very characteristic activity of the present, in which
certain psychological processes are investigated. These in-
vestigations have given rise to a distinct line of research par-
ticipated in by psychologists and biologists. The study of
the way in which animals will react toward light of different
colors, to variations in the intensity of light, to alterations in
temperature, and to various other forms of stimuli are yield-
ing very important results, that enable mvestigators to look
beneath the surface and to make important deductions
regarding the nature of psychological processes.

A line closely allied to experimentation is the application
of statistics to biological processes, such as those of growth,

450 BIOLOGY AND ITS MAKERS

Stature, the law of ancestral inheritance, the statistical study
of variations in spines, markings on shells, etc., etc. (Galton,
Pearson, Davenport).

Other branches of biology that have been greatly devel-
oped by the experimental method are those of bacteriology
and physiological chemistry. The advances in the latter
have greatly widened the horizon of our view regarding the
nature of vital activities, and they compose one of the leading
features of current biological investigation.

Some Tendencies in Anatomical Studies. Cell-Lineage. —
While experimental work occupies the center of the stage,
at the same time great improvements in morphological
studies are evident. It will be only possible, however, to
indicate in a general way the direction in which investigations
are moving. We note, first, as in a previous paragraph, that
the improvement in morphology is generic as well as specific.
Anatomical analysis is being carried to its limits in a number
of directions. The investigations that are connected with
the study of cells afford a conspicuous illustration of this
fact. Studies in cell-lineage have led to an exact determina-
tion of cell-succession in the development of certain animals,
and such studies are still in progress. Great progress also
has been made in the study of physical structure of living
matter. The tracing of cell-lineage is a feat of remarkably
accurate and patient work. But, however much this may
command our admiration, it has been surpassed (as related
in Chapter XI) by investigations regarding the organization
of the egg and the analysis of chromosomes. Boveri, Conk-
lin, Wilson, and others have shown that there are recognizable
areas within the protoplasm of the egg that have a definite
historical relationship to certain structures in process of
development. This is the basis upon which rests the doctrine
of pre-localization of tissue- forming substances within the
protoplasm of the egg.

RECENT TENDENCIES IN BIOLOGY 451

Anatomy of the Nervous System. — In another direction
the progress of anatomical studies is very evident, that is,
investigations of the nervous system and the sense-organs.
The wonderfully complicated relations of nerve elements
have been worked out by Ramon y Cajal. The studies of
Hodge and others upon optical changes occurring within the
cells of the nervous system owing to their functional activity
have opened a great field for investigation. The studies of
Strong, Herrick, and others upon the distribution of nerve-
components in the nerves of the head and the investigations
of Harrison on the growth and the regeneration of nerve-
fibers give illustrations of current tendencies in biological
investigation. The analysis of the central nervous system
into segmental divisions on the basis of functional activity
(Johnston) is still another illustration.

The Application of Biological Facts to the Benefit of Man-
kind.— The practical application of biology to the benefit
of mankind is a striking feature of present-day tendencies.
The activity set on foot by the researches of Pasteur, Koch,
and others has created a department of technical biology of
the greatest importance to the human race.

Under the general heading should be included tne demon-
stration of the connection between insects and the propagation
of yellow fever, malaria, and other disorders; and as an illus-
tration of activity in 1907, we think of the commission recently
appointed to investigate the terrible scourge of the sleeping-
sickness which has been prevalent in Africa. Here also we
would group studies of a pathological character on blood-
immunity, toxin and antitoxin, also studies on the inoculation
for the prevention of various diseases that affect animals and
mankind. Very much benefit has already accrued from the
practical application of biological researches of this nature,
which, in reality, are still in their infancy.

We find the application of biological facts to agriculture

452 BIOLOGY AND ITS MAKERS

in the form of soil-inoculation, in the tracing of the sources
of nitrates in the soil, and studies of the insects injurious to
vegetation; their further application to practical forestry,
and in sanitary sciences. This kind of research is also ap-
plied to the study of food-supply for fishes, as >n the case of
Plankton studies.

The Establishment and Maintenance of Biological Lab-
oratories.— The establishment of seaside biological observa-
tories and various other stations for research have had a great
influence on the development of biology. The most famous
biological station is that founded at Naples (Fig. 123) in 1872
by Anton Dohrn, and it is a gratification to biologists to
know that he still remains its director. This international
station for research has stimulated, and is at present stim-
ulating, the growth of biology by providing the best condi-
tions for carrying on researches and by the distribution of
material which has been put up at the seacoast by the most
skilled preservators. There are many stations modeled
after that at Naples. The Marine Biological Laboratory
at Woods Holl, Mass., is of especial prominence, and
the recently reorganized Wistar Institute of Anatomy at
Philadelphia is making a feature of the promotion of ana-
tomical researches, especially those connected with the anat-
omy of the nervous system.

Laboratories similar to those at the seaside have been
established on several fresh-water lakes. The studies carried
on in those places of the complete biology of lakes, taking
into account the entire surroundings of organisms, are very
interesting and important.

Under this general head should be mentioned stations
under the control of the Carnegie Institution, the various
scientific surveys under the Government, and the United States
Fish Commission, which carries on investigations in the bi-
ology of fishes as well as observations that affect their use

a,

'o
1

454 BIOLOGY AND ITS MAKERS

as articles of diet. The combined output of the various
laboratories and stations of this nature is very considerable,
and their influence upon the progress of biology is properly
included under the head of present tendencies.

The organization of laboratories in our great universities
and their product exercise a wide influence on the progress of
biology, that science having within twenty-five years come to
occupy a position of great importance among the subjects of
general education.

Establishment and Maintenance of Technical Periodicals.
— It is manifestly very important to provide means for the
publication of results and, as needed, to have technical
periodicals established and properly maintained. Their
maintenanc-e can not be effected on a purely commercial
basis, and the result is that some of our best periodicals re-
quire financial assistance in order to exist at all. The sub-
sidizing and support of these periodicals aid materially in
the biological advance. A typical technical periodical is
Schultze's famous Archiv filr Mikroscopische Anatomiey
founded in 1864 by Schultze and continued to the present
time. Into its pages go the highest grade of investigations,
and its continued existence has a salutary influence upon the
progress of biology. The list of technical periodicals would
be too long to name, but among others the Morphologisches
Jahrhuch of Gegenbaur, and Koelliker's Zeitschrijt jilrWissen-
schajtliche Zoologie have had wide influence. In England
the Quarterly Journal of Microscopical Science is devoted to
morphological investigations, while physiology is provided
for in other journals, as it is also in Germany and other
countries. In the United States the Journal oj Morphology ^
passed through seventeen volumes under the editorship of
C. O. Whitman (1842-1910) and was maintained on the high-
est plane of scholarship. The fine execution of the plates
also and the high grade of typographical work gave this

RECENT TENDENCIES IN BIOLOGY 455

Journal a place among the best published scientific periodicals.
After a period of cessation the publication of the Journal
of Morphology was resumed. In the meantime, the A merican
Journal of Anatomy had entered nearly the same field, and
these two give wider opportunity for publication of the increas-
ing number of researches in morphology by American investi-
gators. In the department of experimental work many jour-
nals have sprung up, as Biometrica, edited by Karl Pearson,
Roux's Archiv fur Entwicklungs-Mechanik, the Journal of
Experimental Zoology recently established in the United
States, etc., etc.

Exploration of the Fossil Records. — Explorations of the
fossil records have been recently carried out on a scale never
before attempted, involving the expenditure of large sums,
but bringing results of great importance. The American
Museum of Natural History, in New York City, has carried
on an extensive survey, which has enriched it with wonderful
collections of fossil animals. Besides explorations of the
fossil-bearing rocks of the Western States and Territories,
operations in another locality of great importance are con-
ducted in the Fayiim district of Egypt. The result of the
studies of these fossil animals is to make us acquainted not
only with the forms of ancient life, but with the actual line
of ancestry of many living animals. The advances in
this direction are most niteresting and most important.
This extensive investigation of the fossil records is one of the
present tendencies in biology.

Conclusion. — ^In brief, the chief tendencies in current bio-
logical researches are mainly included under the following
headings: Experimental studies in heredity, evolution, and ani-
mal behavior; more exact anatomical investigations, especially
in cytology and neurology, the promotion and dissemination
of knowledge through biological periodicals; the provision of
better facilities in specially equipped laboratories,^ in the

456 BIOLOGY AND ITS MAKERS

application of results to the benefit of mankind, and in the
investigation of the fossil records.

The atmosphere of thought engendered by the progress of
biology is beneficial in every way. While its progress has
dealt the death-blow to many superstitions and changed
materially views regarding the universe, it is gratifying to
think that it has not been iconoclastic in its influence, but
that it has substituted something better for that which was
taken away. It has given a broader and more wholesome
basis for religion and theories of ethics; it has taught greater
respect for truth and morality. However beneficial this
progress has been in the past, who can doubt that the mission
of biology to the twentieth century will be more important
than to the past, and that there will be embraced in its
progress greater benefits than any we have yet known ?

READING LIST

The books and articles relating to the history of biology are numerous.
Those designated below embrace some of the more readily accessible ones.
While some attention has been given to selecting the best sources, no
attempt has been made to give a comprehensive Hst.

I. GENERAL REFERENCES

CuviER. Histoire des Sciences Naturelles. 5 vols., 1841-1S45. Ex-
cellent, Written from examination of the original documents.

Carus. Geschichte der Zoologie, 1872. Also Histoire de la Zoologie,
1880. A work of scholarship. Contains excellent account of the
Physiologus.

Sachs. History of Botany, 1890. Excellent. Articles in the Botanical
Gazette for 1895 supplement his account by giving the more recent
development of botany.

White. A History of the Warfare of Science with Theology in Christen-
dom, 2 vols., 1900. Good account of Vesalius and the overthrow of
authority in science.

Whewell. History of the Inductive Sciences, vol. II, 1863. Lacks
insight into the nature of biology and the steps in its progress. Men-
tioned because so generally known.

Williams. A History of Science, 5 vols., 1904. Finely illustrated. Con-
tains many defects in the biological part as to the relative rank of the
founders: Vesalius diminished, Paracelsus magnified, etc. Also, the
Story of Nineteenth Century Science, 1900. Collected articles from
Harper^ s Magazine. Good portraits. Uncritical on biological matters.

Thomson. The Science of Life, 1899. An excellent brief history of
biology.

Foster. Lectures on the History of Physiology, 1901. Fascinatingly
written. Notable for poise and correct estimates, based on the use of
the original documents.

Geddes. a Synthetic Outhne of the History of Biology. Proc. Roy. Sac.
Edinb., 1885-1886. Good.

457

45S READING LIST

Richardson. Disciples of ^sculapius, 2 vols., 1901. Collected papers

from The Asclepiad. Sympathetic accounts of Vesalius, Malpighi,

J. Hunter, and others. Good illustrations.
Lankester. The History and Scope of Zoology, in The Advancement

of Science, 1890. Good. Same article in Ency. Brit, under the title

of Zoology.
Spencer. Principles of Biology, 2 vols., 1866.
Hertwig. The Growth of Biology in the Nineteenth Century, Ann.

Rept. Smithson. Inst., 1900.
Buckle. History of Civilization, vol. I, second edition, 1870.
Macgilivray. Lives of Eminent Zoologists from Aristotle to Linnaeus.
Merz. a History of P^uropean Thought in the Nineteenth Century, vol. II,

Scientific Thought, 1903.
RoUTLEDGE. A Popular History of Science. General and uncritical as

to biology.
HOEFER. Histoire de la Zoologie, 1873. Not very good.
Encyclopedia Britannica. Among the more excellent articles arc:

Biology by Huxley; Protoplasm by Geddes; History of Anatomy

by Turner.
Chambers's Encyclopaedia. New Edition. Discerning articles by

Thomson on the Cell-theory, by Geddes on Biology, Evolution.
NouvELLE Biographie Generale. Good articles on the older writers.

Often unreliable as to dates.
Haeckel. The historical chapters in The Evolution of Man, 1892, and

Anthropogenic, fifth edition, 1903. Good.
Haeckel. The History of Creation, vol. I, 1884.
Hertwig. The General Survey of the History of Zoology in his Manual

of Zoology, 1902. Brief but excellent.
Parker and Has well. Text-book of Zoology, 1897. Historical chapter

in vol. II. ,

Nicholson. Natural History, its Rise and Progress in Britain, 1886.

Also Biology.
Pettigrew. Gallery of Medical Portraits, 5 vols. Contains many por-
traits and biographical sketches of men of general influence, as Bichat,

Galen, Malpighi, etc.
PUSCHMANN. Handbuch der Geschichte der Medizin, 3 vols. Good for

topics in anatomy and physiology.
Baas. The History of Medicine, 1889.
Radl. Geschichte der Biologischen Theorien seit dcm Ende des Siebzehn-

ten Jahrhundert, 1905.
Janus. A Periodical devoted to the history of medicine and natural

science, founded in 1896.
Zoologische Annalen. Founded by Max Braun in 1904 in the interests

of the history of zoology.

READING LIST 459

MiTTEILUNGEN ZUR GeSCHICHTE DER MeDIZIN UND NaTURWISSENSCHAF-

TEN, founded 1901.

Studien ZUR Geschichte DER Medizin, Edited by Karl Sudhoflf. Very
important additions to the early history of anatomy, including the Ms.
sources as well as the earliest printed pictures of anatomy.

Surgeon General's Library. The Catalogue should be consulted for
its many biographical references to biologists. The Library is es-
pecially rich in historical documents, as old anatomies, physiologies,
zoologies, etc.

Evolution. The bibliography of Evolution is given below under the
chapters dealing with the evolution theory.

II. SPECIAL REFERENCES

CHAPTER I

Ancient BIOLOGICAL Science : Carus; Botany after 1530, Sachs. Aris-
totle: Cuvier, a panegyric; Lewes, Aristotle — A Chapter from the History
of Science, 1864, a critical study; Huxley, On some Mistakes Attributed
to Aristotle; Macgilivray; Aristotle's History of Animals translated in
Bohn's Classical Library, 1887. Pliny: Magilivray; Thorndike, The
Place of Magic in the Intellectual History of Europe, 1905, chap. III. The
Renaissance: Symonds. Epochs in Biological History: Geddes (see
General List).

CHAPTER II

Vesalius: Roth, Andreas Vesalius Bruxellensis, the edition of 1892,
the standard source of knowledge of Vesalius and his times, contains bibli-
ography, references to his different portraits, the resurrection bone, etc., etc.;
Foster (see General List), Lecture I, excellent; Richardson in Disciples of
yEsculapius, vol. I, contains pictures, his signature, etc.; Pettigrew; White,
vol. II, pp. 51-55; The Practitioner, 1896, vol. 56; The Asclepiad, 1885,
vol. II; De Humani Corporis Fabrica, editions of 1543 and 1555; Opera
Omnia, edited by Boerhaave, 2 vols., 1725; Anatomical Illustration before
Vesalius, Locy, Journ. Morphology, 1911. Galen: Pettigrew; Huxley in
his essay on William Harvey.

CHAPTER III

Harvey: Foster, Lecture H, with quotations, excellent; Dalton, History
of the Circulation; Huxley, William Harvey, a cn'tical essays Harvey's
Works translated by Willis, with biography, Sydenham Society, 1847; Life

460 READING LIST

of Harvey by D'Arcy Power, 1^98; Brooks, Harvey as Embryologist,
Bull. Johns Hop. Hospit., vol. VIII, 1897, good. An Anatomical Disser-
tation upon the Movement of the Heart and Blood in Animals, a facsimile
reproduction of the first edition of the famous De Motu Cordis et Sanguinis,
1628. Privately reproduced by Dr. Moreton in 1894. Very interesting.

CHAPTER IV

Hooke: Biography in encyclopaedias, his microscope in Carpenter, The
Microscope and Its Revelations, 8th ed., 1900.

Malpighi: Richardson, vol. II; Same article in The Asclepiad, vol. X,
1893; Atti, Life and Work, in Italian, 1847, portrait; Pettigrew, vol. II;
Marcello Malpighi e 1' Opera Sua, 1897, a collection of addresses at the
unveiling of Malpighi's monument at Crevalcuore, that by Koelliker ex-
cellent; Locy, Malpighi, Swammerdam, and Leeuwenhoek, Pop. Sci. Mo.,
1901 — protrait and pictures from his works; MacCallum, /. Hop. Univ.
Hospit. Bull. Malpighi's Writings: Opera Omnia, difficult to obtain,
the Robt. Littlebuiy edition, Lond., 1687, contains posthumous papers and
"biography; separate works not uncommon; Traite du Ver a Sole, Mont-
pellier, 1878, contains his life and works.

Swammerdam: Life by Boerhaave in BibHa Naturae, 1737; also Bibel
der Natur, 1752; also The Book of Nature, 1758; Von Baer, Johann
Swammerdam' s Leben und Verdienste um die Wissenschaft, 1864, in
Reden, vol. I; Locy, loc. cit. — portrait.

Leeuwenhoek: New biographical facts in Richardson, vol. I, p. 108;
same article in The Asclepiad, vol. II, 1885, portrait, signature, and other
illustrations; Arcana Naturae; Selected works in English, 1758; Locy,
Pop. Sci. Mo., April, 190 1.

CHAPTER V

Lyonet: The Gentleman's Magazine, LIX, 1789; the famous Traite
Anatomique, etc., 1750, 1752, not rare. Reaumur: Portrait and life in
Les Savants Modernes, p. 332. Roesel: Portrait and biography in Der
monatlich herausgegebenen Insecten Belustigung, part IV, 1761; Zeigler in
Natur und Haus, 1904 — nine figs. Straus-Durckheim: his monograph
on Anatomy of the Cockchafer, rather rare. The Minute Anatomists;
Straus-Durckheim, Dufour, Newport, Leidig, etc., in Miall and Denney's
The Cockroach, 1886.

Discovery of the Protozoa: Leeuwenhoek, Miiller, Ehrenberg,
Dujardin, etc., Kent's Manual of the Infusoria, vol. I. Ehrenberg:
Life by Laue, 1895.

READING LIST 46 1

CHAPTER VI

ThePhysiologus: Carus, White (for titles see General List). Gesner:
Brooks in Pop. Sci. Mo., 1885 — illustrations; Cuvier, loc. cit.; Jardine's
Naturalist's Library, vol. VI; Gesner' s Historia Animalium, 1551-1585.
Aldrovandi: Naturalist's Library, vol. Ill; Macgilivray, /oc. ci/. Jonston:
Macgilivray. Ray: Macgilivray; Nicholson; Memorial of, in the Ray
Society, 1846; Correspondence of, Ray Soc, 1848. Linn^us : Mac-
gilivray; Janus, vol. 8, 1903; Cuvier, loc. cit.; Agassiz, Essay on Classi-
fication, 1859; Jubilee at Upsala, Science, Apl. 26, 1907; Caddy, Through
the Fields with Linnaeus, 1887; The Systema Naturae, especially the tenth
edition, 1758. Leuckart: Archives de Parasit., vol. I, no. 2; Nature,
1898. General Biological Progress from Linn^us to Darwin:
Geddes, Proc. Roy. Soc. Edinb., vol. 13, 1884-1886.

CHAPTER VII

Camper: Naturalist's Library, vol. VII; Vorlesungen, by his son, with
short sketch of his life, 1793; Cuvier, loc. cit.; Kleinere Schriften, 2 vols,
with copper plates illustrating brain and ear of fishes, etc., 1 782-1 785.
John Hunter: The Scientific Works of, 2 vols., 1861; The Asclepiad, vol.
VIII, 1 891; the same article with illustrations in Richardson, loc. cit.; Petti-
grew, loc. cit. ViCQ d'Azyr: Cuvier, loc. cit.; Huxley in Life of Owen,
p. 289; His works in 6 vols., 1805. Cuvier: Life by Flourens; Memoirs by
Mrs. Lee, 1833; Buckle, Hist. Civ., vol. I, p. 633 et seq.; Lettres de Geo.
Cuviera C. M. PaiT, 1788-1792, translated from the German, 1858. Cuvier's
numerous writings — The Animal Kingdom, Lemons d'Anat. Comparee, etc.
— are readily accessible. H. Milne-Edwards : Biographical sketch in A nn.
Kept. Smithson. Inst, for 1893. Lacaze-Duthiers: Life with portraits
in Archives de Zool. Experiment., vol. 10, 1902. Richard Owen: Life and
Letters, 2 vols., 1894; Clark, Old Friends at Cambridge and Elsewhere,
p. 349 et seq. J. Fr. Meckel: Carus, loc. cit. Gegenbaur: Erlebtes und
Erstrebtes, portrait, 1901; Anat. Anz., vol. 23, 1903; Ann. Rept. Smithson.
Inst., 1904. Cope: Osborn in The Century, vol. 33, 1897; Gill, Edward
Drinker Cope, Naturalist, A Chapter in the History of Science, Am. Natur-
alist, 1897; Obituary notice, with portraits, Am. Naturalist, 1897; Pop.
Sci. Mo., vol. 19, 1881.

CHAPTER VIII

Bichat: Pettigrew; Buckle, Hist. Civ., vol. I, p. 639; The Hundred
Greatest Men; Les Savants Modernes, p. 394; TTie Practitioner, vol. 56,
1896. Koelliker: His Autobiography, Erinnerungen aus Meinem

462 READING LIST

Leben, 1899, several portraits, interesting; Weldon, Life and Works in
Nature, vol. 58, with fine portrait; Sterling, Ann. Rept. Smithson. Inst., 1905^
Schultze: Portrait and Necrology by Schwalbe in Archiv jiir Mikroscop^
Anat., vol, 10, 1874; See further under chapter XII. Virchow: /. Hop
Univ. Circulars, vol. XI, 189 1, Celebration of Seventieth Birthday of Virchow
Addresses by Osier, Welch, and others; Jacobi, Medical Record, N. y!
vol. XX, 1881, good; Israel, in Ann. Rept. Smithson. Inst., 1902. Leydig,
Brief sketch in his Horae Zoologicae, 1902. Ramon y Cajal: Portrait in*
Tenth Anniversary of Clark University, 1899.

CHAPTER IX

The best brief account cf the Rise of Physiology in Verworn's General
Physiology, 1899. More recent German editions of the same work. His-
torical outline in Rutherford's Text-Book of Physiology, 1880. Galen's
Physiology: Verworn. Harvey: See references under Chapter III; The
analysis of his writings by Willis in The Works of Harvey, translated into
English, Sydenham Soc, 1847; See also Dr. Moreton's facsimile repro-
duction of the first edition (1628) of De Motu Cordis et Sanguinis, 1894.
Haller: Fine portrait in his Elementa Physiologiae, 1758; English trans-
lations of the Elementa. Charles Bell: Pettigrew; Good summary in
Foster's Life of Claude Bernard, p. t,^ et seq. Johannes Muller: His
life, complete list of works, etc., in Gedachtnissrede auf Johannes Muller
by Du Bois-Reymond, i860; Eloge by Vichow in Edinburgh Med. Journ.,
vol. 4; Picture of his monument in Coblenz, Archiv /. Mik. Anat., vol. 55;
Brief e von J. Muller an Andres Retzius (1830-185 7), 1900; His famous
Handbuch der Physiologie and English translations should be inspected.
Ludwig: Burdon-Sanderson, Ludwig and Modern Physiology, Sci. Progress,
vol. V, 1896; The same article in Ann. Rept. Smithson. Inst., 1896. Claude
Bernard: Life by M. Foster, 1899, excellent.

CHAPTER. X

Good general account of the Rise of Embryology in Koelliker's Embryolo-
gie, 1880; Minot, Embryology and Medical Progress, Pop. Sci. Mo., vol. 69,
1906; Eycleshymer, A Sketch of the Past and Future of Embryology,
St. Louis Med. Rev., 1904. Harvey: As fembryologist, Brooks in /. Hop.
Univ. Hospit. Bull., vol. VIII, 1897. See above. Chaps. Ill and IX
for further references to Harvey. Malpighi: in Embryology, Locy in
Pop. Sci. Mo., 1905 — portrait and selected sketches from his embryological
treatises. Wolff: Wheeler, Wolfif and the Theoria Generationis, in
Woods Holl Biological Lectures, 1898; Kirchoff in Jenaisclie Zeitschr.y

READING LIST 463

vol. 4, 1868; Waldeyer, Festrede in Sitzbr. d. K. Preus. Akad. d. Wissen-
schaft., 1904; Haeckel in Evolution of Man, vol. I, 1892. Bonnet and
Pre-delineation: Whitman, Bonnet's Theory of Evolution, also Evolution
and Epigenesis, both in Woods HoU Biological Lectures, 1895. VoN
Baer: Leben und Schriften, his autobiography (1864), 2d edition, 1886;
Life by Steida, 1886; Obituary, Proc. Roy. Soc, 1878; Waldeyer in Allg.
Wien. Med. Ztg., 1877; Nature, vol. 15; Life by St5lzle, 1897; Haeckel,
loc. cit., vol. I; Locy, V. Baer and the Rise of Embryology, Pop. Sci. Mo.,
1905; Fine portrait as young man in Harper's Mag. for 1899; Rev. Scient.,
1879. Kowalevsky: Lankester in Nature, vol. 66, 1902; Portrait and
biog. in Ann. Mus. Hist. Nat. Marseille, vol. 8, 1903. Balfour: M.
Foster in Nature, vol. 29, 1882; Also Life with portrait in the Memorial
Edition of Balfour's Works; Waldeyer in Arch. f. Mik. Anat., vol. 21, 1882;
Osborn Recollections, with portrait. Science, vol. 2, 1883. His: Mall in
Am. Journ. Anat., vol. 4, 1905; Biography in Anat. Anz., vol. 26, 1904.

CHAPTER XI

The Cell-Doctrine by Tyson, 1878. The Cell-Theory, Huxley, Medico-
chir. Review, 1853, also in Scientific Memoirs, vol. I, 1898; The Modern
Cell-Theory, M'Kendrick, Proc. Phil. Soc. Glasgow, vol. XIX, 1887; The
Cell-Theory, Past and Present, Turner, Nature, vol. 43, 1890; The Cell-
Doctrine, Burnett, Trans. Am. Med. Assn., vol. VI, 1853; First illustration
of cells in Rob't Hooke's Micrographia, 1665, 1780, etc.; The Cell in De-
velopment and Inheritance, Wilson, 1896; Article Cell, in Chambers's (New)
Cyclopaedia, by Thomson. Schleiden: Sketch of, Pop. Sci. Mo., vol.
22, 1882-1883; Sachs' Hist, of Botany 1890; Translation of his original
paper of 1838 (Ueber Phytogenesis) — illustrations — Sydenham Soc, 1874.
Schwann: Life, Pop. Sci. Mo.,\o\. 37, 1900; Sa Vie et Ses Travaux,
Fredericq, 1884; Nachruf, Henle, Archiv f. Mik. Anat., vol. 21, 1882;
Lankester, Nature, vol. XXV, 1882; The Practitioner, vol. 49, 1897; The
Catholic World, vol. 71, 1900. Translation of his contribution of 1839
(Mikroscopische Untersuchungen ueber die Uebereinstimmung in der Struc-
tur und dem Wachstum der Thiere und Pflanzen), Sydenham Soc, 1847.

CHAPTER XII

On the Physical Basis of Life, Huxley, 1868; Reprint in Methods and
Results, 1894. Article Protoplasm in Ency. Brit, by Geddes. Dujardin:
Notice Biographique, with portraits and other illustrations, Joubin, Archives
de Parasitol., vol. 4, 1901; portrait of Dujardin hitherto unpublished. Du-
jardin's original description of Sarcode, Ann. des Sci. Nat. {Botanique^,

464 READING LIST

vol. 4, p. 367, 1835. Von Mohl: Sachs' History of Botany, 1890. Trans-
lation of his researches, Sydenham Soc, 1847. Cohn: Blatter der Er-
innerung, 1898, with portrait. Schultze: Necrology, by Schwalbe in
Archiv /. Mik. Anat., vol. 10, 1874, with portrait. Schultze's paper found-
ing the protoplasm doctrine in Archiv j. Anat. und Phys., 1861, entitled
Ueber Muskelkorperchen und das was man eine Zelle zu nennen habe.

CHAPTER XIII

Spontaneous Geneziation: Tyndall, Pop. Set. Mo., vol. 12, 1878;
Also in Floating Matter of the Air, 1881 ; J. C. Dalton in iV. F. Med. Journ.y
1872; Dunster, good account in Proc. Ann Arbor Sci. Assn., 1876; Hux-
ley, Kept. Brit. Assn. for Adv. Sci., 1870, republished in many journals,
reprint in Scientif. Memoirs, vol. IV, 1901. Redi: Works in 9 vols., 1809-
181 1, with life and letters and portraits; Good biographical sketch in
Archives de Parasitol., vol. I, 1898; Redi's Esperienze Intorno Alia Genera-
zione DeglTnsetti, 2 plates, first edition, 1668, in Florence, 40; reprinted
at various dates, not uncommon; English translation by Mab. Bigelow,
1909. Spallanzani: Foster, Lects. on Physiol.; Huxley, loc. cit.; Dunster,
loc. cit.; L'Abbato Spallanzani, by Pavesi, 1901, portrait. Pouchet: His
treatise of historical importance — Heterogenic, ou Traite de la Generation
Spontanee, base sur des Nouvelles Experiences, 1859. Pasteur: Life by
Rene Vallery-Radot, 2 vols., 1902; Percy and G. Frankland, 1901; Pasteur
at Home, illustrated, Tarbell in McClure's Mag., vol. 1, 1893; Also McClure's,
vol. 19, 1902, review of Vallery-Radot's Life of Pasteur; Nature, vol. 52,
1895; Les Savants Modernes, p. 316; Life by his son-in-law, translated by
Lady Hamilton, 1886; Sketches of Pasteur, very numerous. Bacteriology:
Woodhead, Bacteria and their Products, 1891; Fraenkel, Text-Book of
Bacteriology, 1891; Prudden, The Story of Bacteria, etc., 1891. Germ-
Theory OF Disease: Crookshank's Bacteriology, 3d edition, 1890. Koch:
Pop. Sci. Mo., vol. s6y 1889; Review of Reviews, vol. 2, 1890; Sketches and
references to his discoveries numerous. Lister: Pop. Sci. Mo., vol. 52,
1898; Review of Reviews, vol. 14, 1896; celebration of Lister's 80th birthday,
Pop. Sci. Mo., June, 1907; Janus, vol. 5, 1900. The New Microbe Inocula-
tion of Wright, Harper's Mag., July, 1907.

CHAPTER XIV

The History and Theory of Heredity, J. A. Thomson, Proc. Roy. Soc.
Edinb., vol. XVI, 1889; Chapter on Heredity in Thomson's Science of Life,
1899; 3^1so in his Study of Animal Life, 1892; Heredity and Environment in
the Development of Men, Conklin, 1915. Mendel: Mendel's Principles
of Heredity, with translations of his original papers on hybridization, Bate-

READING LIST 465

son, 1902; Mendel's Versuche iiber Pflanzenhybriden, two papers (1865 and
1869), edited by Tschermak, 1901; Ann. Rept. SmUhson. Inst., 1901-1902;
Pop. Sci. Mo., vol. 62, 1903; vol. 63, 1904; Science, vol. 23, 1903. Galton:
Pop. Sci. Mo., vol. 29, 1886; Nature, vol. 70, 1907; Memories of my Life,
1908; Galton's Natural Inheritance, 1889. Weismann: Brief Autobiography,
with portrait, in The Lamp, vol. 26, 1903; Solomonsen, Bericht iiber die
Feier des 70 Geburtstages von August Weismann, 1904; Weismann's The
Germ-Plasm, 1893, and The Evolution Theory, 1904.

CHAPTER XV

History of Geology and Paleontology, Zittel, 1901. The Founders of
Geology, Geikie, 2d edition, 1905. History and Methods of Paleonto-
logical Discovery, Marsh, Proceed. Am. Adv. Sci., 1879. Same article in
Pop. Sci. Mo., vol. 16, 1879-1880. The Rise and Progress of Paleontology,
Huxley, Pop. Sci. Mo., vol. 20, 1882. Lyell: Charles Lyell and Modern
Geology, Bonney, 1895; Sketch in Pop. Sci. Mo., vol. I, 1872, also vol.
20, 1881-1882. Owen: Life of, by his grandson, 2 vols., 1894; See also
above under Chapter VIL Agassiz: Life and Correspondence, by his
wife, 2 vols., 1885; Life, letters and works, Marcou, 2 vols., 1896; What
we Owe to Agassiz, Wilder, Pop. Sci. Mo., July, 1907; Agassiz at Penikese,
Am. Nat., 1898. Cope: A Great NaturaHst, Osborn in The Century, 1897;
See above, under Chapter VII, for further references. Marsh: Pop, Sci. Mo.,
rol. 13, 1878; Sketches of. Nature, \o\. 59, 1898-99; Science, vol. 9, 1899;
Am. J. Sci., vol. 157, 1899. Zittel: Biographical Sketch with portrait,
Schuchert, Ann. Rept. Smithson. Inst., 1903-1904. Osborn, Papers on
Paleontological Discovery in Science from 1899 onward; The Age of Mam-
mals, 1910. The Faylim Expedition of the Am. Museum of Nat, History,
Science, March 29, 1907.

Note. Since the four succeeding chapters deal with the Evolution
Theory, it may be worth while to make a few general comments on the liter-
ature pertaining to Organic Evolution. The number of books and articles
is very extensive, and I have undertaken to sift from the great number a
limited list of the more meritorious. Owing to the prevalent vagueness
regarding evolution theories, one is likely to read only about Darwin and
Darwinism. This should be avoided by reading as a minimum some good
reference on Lamarck, Weismann, and De Vries, as well as on Darwin.
It is well enough to begin with Darwin's Theory, but it is not best to take
his Origin of Species as the first book. To do this is to place oneself fifty
years in the past. The evidences of Organic Evolution have greatly multi-
plied since 1859, and a better conception of Darwin's Theory can be ob-
tained by reading first Romanes's Darwin and After Darwin, vol. L This to
be followed by Wallace's Darwinism, and, thereafter, the Origin of Species

466 READING LIST

may be taken up. These will give a good conception of Darwin's Theory,
and they should be followed by reading in the order named: Packard's
Lamarck; Weismann's The Evolution Theory; and De Vries's The Origin
of Species and Varieties by Mutation. Simultaneously one may read with
great profit Osbom's From the Greeks to Darwin, and Kellogg's Darwinism
To-Day, 1907.

CHAPTER XVI

General: Romanes, Darwin and After Darwin, 1892, vol. I, chaps.
I-V; Same author. The Scientific Evidences of Organic Evolution; Weis-
mann Introduction to the Evolution Theory, 1904; Osborn, Alte und Neue
Probleme der Phylogenese, Ergehnisse der Anat. u. Entwickel., vol. Ill, 1893;
Ziegler, Ueber den derzeitigen Stand der Descendenzlehre in der Zoologie,
1902; Jordan and Kellogg, Evolution and Animal Life, 1907, chaps. I and
XIV. Evolutionary Series — Shells: Romances, loc. cit.; Hyatt, Trans-
formations of Planorbis at Steinheim, Proc. Am. Ass. Adv. Sci., vol. 29, 1880.
Horse: Lucas, The Ancestry of the Horse, McClure's Mag., Oct., 1900;
Huxley, Three Lectures on Evolution, in Amer. Addresses. Embryology —
Recapitulation Theory: Marshall, Biolog. Lectures and Addresses,
1897; Vertebrate Embryology, 1892; Haeckel, Evolution of Man, 1892.
Primitive Man: Osborn, Discovery of a Supposed Primitive Race of
Men in Nebraska, Century Mag., Jan., 1907; Haeckel, The Last Link,
1898. Huxley, Man's Place in Nature, collected essays, 1900; published
in many forms. Romanes, Mental Evolution in Man and Animals.

CHAPTER XVII

Lamarck: Packard, Lamarck, the Founder of Evolution, His Life
and Work, with Translations of his Writings on Organic Evolution, 1901;
Lamarck's Philosophic Zoologique, 1809. Recherches sur I'Organisation
des corps vivans, 1802, contains an early, not however the first statement of
Lamarck's views. For the first published account of Lamarck's theory
see the introduction to his Systeme des Animaux sans Vertebres, 1801.
Neo-Lamarckism: Packard, loc. cit.; also in the Introduction to the
Standard Natural History, 1885; Spencer, The Principles of Biology, 1866
— based on the Lamarckian principle. Cope, The Origin of Genera, 1866
Origin of the Fittest, 1887; Primary Factors of Organic Evolution, 1896,
the latter a very notable book. Hyatt, Jurassic Ammonites, Proced. Bost
Sci. Nat. Hist., 1874. Osborn, Trans. Am. Phil. Soc, vol. 16, 1890. Eigen
mann. The Eyes of the Blind Vertebrates of North America, Archiv f.
Entwickelungsmechanik, vol. 8, 1899.

Darwin's Theory (For biographical references to Darwin see below

READING LIST 467

under Chapter XIX): Wallace, Darwinism, 1889; Romanes, Darwin
and After Darwin, vol. I, 1892; Metcalf, An Outline of the Theory of
Organic Evolution, 1904, good for illustrations. Color; Poulton, The
Colors of Animals; Chapters in Weismann's The Evolution Theory, 1904.
Mimicry; Weismann, loc. cit. Sexual Selection: Darwin, The Descent
of Man, new ed., 1892. Inadequacy or Nat. Selection: Spencer, The
Inadequacy of Natural Selection, 1893; Morgan, Evolution and Adapta-
tion, 1903. Kellogg, Darwinism To-day, 1907, contains a good account
of criticisms against Darwinism.

CHAPTER XVIII

Weismann's The Evolution Theory, translated by J. A. and Margaret
Thomson, 2 vols., 1904, contains the best statement of Weismann's views.
It is remarkably clear in its exposition of a complicated theory. The
Germ-Plasm, 1893; Romanes's An Examination of Weismannism, 1893.
Inheritance of Acquired Characters: Weismann's discussion, loc. cit.,
vol. II, very good. Romanes's Darwin and After Darwin, vol. II. Per-
sonality OF Weismann: Sketch and brief autobiography, in The Lamp.
vol. 26, 1903, portrait; Solomonsen, Berichtiiber die Feier des 70 Geburts-
tages von August Weismann, 1905, 2 portraits.

Mutation-Theory of De Vries: Die Mutations-Theorie, looi;
Species and Varieties, their Origin by Mutation, 1905; Morgan, Evolution
and Adaptation, 1903, gives a good statement of the Mutation Theory,
which is favored by the author; Whitman, The Problem of the Origin of
Species, Congress of Arts and Science, Universal Exposition, St. Louis, 1904;
Davenport, Evolution without Mutation, Journ. Exp. ZooL, April, 1905.

CHAPTER XIX

For early phases of Evolutionary thought consult Osborn, From the
Greeks to Darwin, 1894, and Clodd, Pioneers of Evolution, 1897. Suarez
and the Doctrine of Special Creation: Huxley, in Mr. Darwin's
Critics, Cont. Rev., p. 187, reprinted in Critiques and Addresses, 1873.
Buffon: In Packard's Life of Lamarck, chapter 13. E. Darwin:
Krause's Life of E. Darwin translated into English, 1879; Packard, loc.
cit. Goethe: Die Idee der Pflanzenmetamorphose bei Wolff und bei
Goethe, Kirchoff, 1867; Goethe's Die Metamorphose der Pflanzen, 1790.
Oken: His Elements of Physiophilosophy, Ray Soc, 1847. Cuvier and
St. Hilaire: Perrier, La Philosophie Zoologique avant Darwin, 1884;
Osborn, loc. cit. Darwin and Wallace: The original communications of
Darwin and Wallace, with a letter of transmissal signed by Hooker and Lyell,

468 READING LIST

published in the Trans. LinncBan Soc. for 1858, were reprinted in the Pop.
Set. Mo., vol. 60, igoi; Judd, The Coming of Evolution, 1910. Darwin:
Personality and biography (For references to his theory see under Chapter
XVII); Life and letters by his son, 3 vols., 1887, new ed., 1896; More Letters
of Charles Darwin, 2 vols., 1903; Chapter in Marshall's Lectures on the Dar-
winian Theory; Darwin, Naturalist's Voyage around the World, 1880;
Gould, Biographical Clinics, for Darwin's illness due to eye-strain; Poulton,
Chas. Darwin, and the Theory of Natural Selection, 1896. Wallace: My
Life, 2 vols., 1905; The Critic, Oct., 1905. Huxley: Life and Letters by his
Son, 1901; Numerous sketches at the time of his death, 1895; in Nature,
Nineteenth Century, Pop. Sci. Mo., etc., etc. Haeckel. His Life and Work
by Bolsche, 1906.

CHAPTER XX

It is deemed best to omit the references to Technical papers upon which
the summaries of recent tendencies are based. Morgan's Experimental
Zoology, 1907. Jennings, Behavior of the Lower Organisms, 1906. Mos-
quitoes and other insects in connection with the transmission of disease,
see Folsom, Entomology, 1906, chapter IX, p. 299. Biological Lab-
oratories: Dean, The Marine Biological Stations of Europe, Ann. Rept.
Smithson. Inst., 1894; Marine Biolog. Station at Naples, Harper's Mag.,
1901; The Century, vol, 10 (Emily Nunn Whitman); WilHams, A
History of Science, vol. V, chapter V, 1904; Am. Nat., vol. 31, 1897;
Pop. Sci. Mo., vol. 54, 1899; ihid., vol. 59, 1901. Woods HoU Station — A
Marine University, Ann. Rept. Smithson. Inst., 1902.

INDEX

INDEX

Abiogenesis, 277

Acquired characters, inheritance of,
315; Weismann on, 404

Agassiz, essay on classification, 137;
agreement of embryological stages
and the fossil record, 336; fossil
fishes, 336; portrait, 336

Aldrovandi, 115

Alternative inheritance, 317

Amphimixis, the source of varia-
tions, 402

Anatomical sketches, the earliest,
32; from Vesa'ius, 31, 33

Anatomical studies, recent tenden-
cies of, 450

Anatomy, of Aristotle, 23; begin-
nings of, 23; earliest known illus-
trations, 32; of Galen, 24; of the
Middle Ages, 24; comparative,
rise of, 141- 165; of insects,
Dufour, log; Lyonet, 91; Mal-
pighi, 63; Newport, 100; Reau-
mur, 96; Roesel, 96; Straus-
Diirckheim, 96; Swammerdam,
70, 73-77; minute, progress of,
89-104; of plants. Grew, 56;
Malpighi, 66

Ancients, return to the science of,
112

Animal behavior, studies of, 451

Animal kingdom of Cuvier, 133

Aquinas, St. Thomas, on creation,

417
Arcana Naturae, of Leeuwenhoek,

78
Aristotle, 9-15; books of, 13; errors
of, 13; estimate of, 10; extensive
knowledge of animals, 12; the
founder of natural history, 9; in-
fluence of, 15; personal appear-
ance, 13, 14; portrait, 14; posi-
tion in the development of science,
II
Arrest of inquiry, efifect of, 1 7
Augustine, St., on creation, 417
Authority declared the source of
knowledge, 18

B

Bacteria, discovery of, 276; disease-
producing, 300; and antiseptic
surgery, 303; nitrifying, of the
soil, 305

Bacteriology, development of, 276

Baer, Von, and the rise of embryol-
ogy, 195-236; his great classic on
development of animals, 214; and
germ-layers, 218; makes embryol-
ogy comparative, 220; and Pan-
der, 218; period in embryology,
214-226; portraits, 216, 217; his
rank in embryology, 220; his es-
pecial service, 217; sketches from
his embryological treatise, 221

Balfour, masterly work of, 226; his
period in embryology, 226-232;
personality, 228; portrait, 227;
tragic fate, 228; university career,
227

Bary, H. A. de, 271; portrait, 272

Bassi, and the germ-theory of dis-
ease, 294

Bell, Charles, discoveries on the ner-
vous system, 183; portrait, 184

Berengarius, 26

Bernard, Claude, in physiology, 190;
personality, 191; portrait, 191

Biblia Naturae of Swammerdam, 73

Bichat, and the birth of histology,
166-178; Buckle's estimate of,
166, 167; education, 167; in
Paris, 167; personality, 168; phe-
nomenal industry, 168; portrait,
169; results of his work, 170;
writings, 170; successes of, 170

Binomial nomenclature of Linnaeus,
126

Biological facts, application of, 451

Biological laboratories, establish-
ment and maintenance of, 452;
the station at Naples, 452; picture
of, 453; the Woods HoU station,
452

Biological periodicals, 454

Biological progress, continuity of,
442; atmosphere engendered by.

471

472

INDEX

456; from Linnaeus to Darwin,
138-140 .

Biology, defined, 4; domain of, 4, 5;
epochs of, 20; progress of, 3, 5;
applied, 451

Boerhaave, quoted, 71, 72; and
Linnaeus, 122

Bois-Reymond Du, 189; portrait,
189

Bones, fossil, 324, 326

Bonnet, and emboitcment, 208; op-
position to Wolff, 211; portrait,
212

Books, the notable, of biology, 443

Brown, Robert, discovers the nu-
cleus in plant'cells, 243

Buckland, 326

Buckle, on Bichat, 166, 167

Buffon, 129, 419; portrait, 420; po-
sition in evolution, 420

Caesalpinus, on the circulation, 50

Cajal, Ramon y, 176; portrait, 176

Calkins, on protozoa, 109

Camper, anatomical work of, 143;
portrait, 144

Carpenter, quoted, 170

Carpi, the anatomist, 26

Castle, experiments on inheritance,
318

Catastrophism, theory of, Cuvier,
328; Lyell on, si3

Cell, definition of, 258; diagram of,
257; earliest known pictures of,
238, 239; in heredity, 257

Cell-lineage, 234, 450

Cell-theory, announcement of, 242;
effect on embryology, 222, 224;
founded by Schleiden and
Schwann, 242; Schleiden's con-
tribution, 247; Schwann's trea-
tise, 248; modifications of, 250;
\ ague foreshadowings of, 237

Child, studies on regulation, 448

Chromosomes, 254, 313

Circulation of the blood, Harvey,
46, 47; Servetus, 50; Columbus,
50; Caesalpinus, 50; in the capil-
laries, 84; Leeuwenhoek's sketch
of, 83; Vesalius on, with illustra-
tion, 49

Classification of animals, tabular
view of, T37-138

Cohn, portrait, 271

Color, in evolution, 392

Columbus, on the circulation, 50

Comparative anatomy, rise of, 141-
165; becomes experimental, 165

Cope, in comparative anatomy, 165;
portrait, 338; important work in
palaeontology, 339, 441

Creation, Aquinas on, 417; St.
Augustine on, 416; special, 418;
evolution the method of, 350

Cuvier, birth and early education,
149; and catastrophism, 328;
comprehensiveness of mind, 154;
correlation of parts, 133; debate
with St. Hilaire, 424; domestic
life, 155; forerunners of, 143;
founds comparative anatomy, 154;
founder of vertebrate pahuontol-
ogy, 327; his four branches of the
animal kingdom, 132; goes to
Paris, 151; life at the seashore,
150; opposition to Lamarck, 422;
portraits, 152, 153; physiognomy,
152; and the rise of comparative
anatomy, 141-156; shortcomings
of, 156; successors of, 156; type-
theory of, 133

Darwin, Charles, his account of the
way his theory arose, 435; factors
of evolution, 386; habits of work,
432; home life, 431; at Down,
434; ill health, 434; naturalist on
the Beagle, 433; natural selection,
389; opens note-book on the origin
of species, 434; personality, 430;
portraits, 387, 431; parallelism in
thought with Wallace, 435; pub-
lication of the Origin of Species^
437; his other works, 397, 437;
theory of pangenesis, 307; varia-
tion in nature, 388; the original
drafts of his theory sent by
Hooker and Lyell to the Linnaean
Society, 428-430; working hours,
434; summary of his theory, 411

Darwin, Erasmus, 421; portrait,
421

Darwinism and Lamarckism con-
fused, 397; not the same as or-
ganic evolution, 349

Davenport, experiments, 321

Deluge, and the deposit of fosals,
32s

INDEX

473

De Varies, mutation theory of, 408;

portrait, 409; summary, 411
Dufour, Leon, on insect anatomy, 100
Dujardin, 250, 262; discovers sar-

code, 250, 266; portrait, 265;

writings, 264

Edwards, H. Milne-, 157; portrait,

157

Ehrenberg, 106, 107; portrait, 108

Eimer, 413

Embryological record, interpreta-
tion of, 229

Embryology, Von Baer and the rise
of, 194-236; experimental, 232;
gill-clefts and other rudimentary
organs in embryos, 363; theoret-
ical, 235

Epochs in biological history, 20

Evolution, doctrine of, generalities
regarding, 347; controversies re-
garding the factors, 348, 375; fac-
tors of, 374; effect on embryology,
225; on palaeontology, 334; na-
ture of the question regardmg,
350; a historical question, 350;
the historical method in, 350;
sweep of, 372; one of the greatest
acquisitions of human knowledge,
372; predictions verified, 373;
theories of, 375; Lamarck, 375;
Darwin, 392; Weismann, 398;
De Vries, 408; order of the best
reading, 465; summary of evo-
lution theories, 410; vagueness
regarding, 348

Evolutionary series, 353; shells, 353;
horses, 356

Evolutionary thought, rise of, 415-
441 ; views of certain fathers of the
church, 416

Experimental observation, intro-
duced by Harvey, 39-53

Experimental work in biology, 447

Fabrica, of Vesalius, 32

Fabricius, Harvey's teacher, 41;

portrait, 43
Factors of evolution, 375
Fallopius, 37; portrait, 37
Flood, fossils ascribed to, 325
Fossil remains, the science of, 322-

343; bones, 324, 327; horses in

America, 357; collections in New
Haven, 357; in New York, 357;
man, 342, 366; Neanderthal skull,
368; ape-like man, 369; remains
of man: Neanderthal, 368; Java,
369; Heidelberg, 369; Piltdown,
370

Fossil remains an index to past his-
tory, 331

Fossils, arrangement in strata, 330;
ascribed to the flood, 325; their
comparison with living animals,
326; from the Fayum district, 343;
method of collecting, 342; nature
of, 324; determination of, by
Cuvier, 327; Da Vinci, 324;
Steno, 324; strange views re-
garding, 322

Galen, 23, 180; portrait, 25

Gal ton, law of ancestral inheritance,
321; portrait, 320

Geer, De, on insects, 95

Gegenbaur, 163; portrait, 164

Generation, Wolff's theory of, 210

Germ-cells, organization of, 210

Germ-layers, 218

Germ-plasm, continuity of, 399;
complexity of, 401 ; the hereditary
substance, 321; union of germ-
plasms the source of variations, 402

Germ-theory of disease, 293

Germinal continuity, 224, 309; doc-
trine of, 224, 312, 399

Germinal elements, 306

Germinal selection, 403

Germinal substance, 311

Gesner, 112; personality, 113; por-
trait, 114; natural history of, 113

Gill-clefts in embryos, 363

Goodsir, 174

Grew, work of, 56

Haeckel, 439; portrait, 440

Haller, fiber-theory, 242; opposition
to Wolff, 211; in physiology, 181;
portrait, 182

Harvey, and experimental observa-
tion, 39-53; his argument for the
circulation, 51; discovery of the
circulation, 47; his great classic,
46; education, 40; in embryology,
198; embryological treatise, 199,

474

INDEX

200; frontispiece from his genera-
tion of animals (1651), 201; in-
fluence of, 52; introduces exper-
imental method, 47; at t*adua, 41;
period in physiology, 180; per-
sonal appearance and qualities,
42, 44, 45; portrait, 44; prede-
cessors of, 48; question as to his
originaMty, 46; his teacher, 43;
writings, 45

Heredity, 306; a cellular study, 257;
according to Darwin, 308; Weis-
mann, 310; application of statis-
tics to, 315; inheritance of ac-
quired characters, 315; steps in
advance of knowledge of, 309

Hertwig, Oskar, portrait, 231; ser-
vice in embryology, 2^2; Rich-
ard, quoted, 125

Hilaire, St., portrait, 424; see St.
Hilairc

His, Wilhelm, 232; portrait, 233

Histology, birth of, 166-178; Bichat
its founder, 170; normal and
pathological, 172; text-books of,
177 ^

Hookc, Robert, 55; his microscope
illustrated, 55

Hooker, letter on the work of Dar-
win and Wallace, 428-430

Horse, evolution of, 356

Human ancestry, links in, 366-372

Human body, evolution of, 365

Human fossils, 342, 367

Hunter, John, 144; portrait, 145

Huxley, in comparative anatomy,
161; influence on biology, 438; in
palaeontology, 337; portrait, 438

Inheritance, alternative, Mendel,
317; ancestral, 321; Darwin's
theory of, 307; material basis of,
312-314; nature of, 306

Inheritance of acquired characters,
315; Lamarck on, 383; Weis-
mann on, 404

Inquiry, the arrest of, 17

Insects, anatomy of, Dufour, 106;
Malpighi, 63; illustration, 65;
Newport, 100; Leydig, 102;
Straus-Diirckheim, 96; Swammer-
dam, 70, 75; illustration, 76; theol-
ogy of, 91

Isolation, 413

Jardin du Roi changed to Jardin des

Plantes, 378
Jennings, on animal behavior, 109,

441
Jonston, 114

K

Klein, 118

Koch, Robert, discoveries of, 300;

portrait, 301
Koelliker, in embryology, 224; in

histology, 171; portrait, 173
Kowalevsky, in embryology, 224;

portrait, 225

L

Lacaze-Duthiers, 158; portrait, 159
Lamarck, changes from botany to
zoology, 378; compared with
Cuvier, 329; education, 377; first
announcement of his evolutionary
views, 381; forerunners of, 419;
first use of a genealogical tree, 131;
founds invertebrate pala;ontology,
328; on heredity, ^8^^; laws of
evolution, 382; military exi)cri-
ence, 376; opposition to, 422;
Philosophic Zoologique, 381; por-
trait, 373; position in science, 132;
salient points in his theory, 384;
his theory of evolution, 380; com-
pared with that of Darwin, 396,
397; time and favorable condi-
tions, 384; use and disuse, 380
Lecuwenhoek, 77-87; new bio-
graphical facts, 78; capillary
circulation, 84, 85, sketch of, 83;
comparison with Malpighi and
Swammerdam, 87; discovery of
the protozoa, 105; other discov-
eries, 85; and histology, 178; his
microscopes, 81; pictures of, 82,
83; occupation of, 78; portrait,
79; scientific letters, 8$; theoreti-
cal views, 86
Leibnitz, 208

Leidy in palaeontology, 339
Lesser's theology of insects, 91
Leuckart, 136; portrait, 136
Leydig, 102; anatomy of insects,
102; in histology, 175; portrait,

.175
Linnaean system, reform of, 130-138
Linnaeus, 1 18-130; binomial nomen-
clature, 127; his especial service,

INDEX

475

126; features of his work, 127,
1 28; his idea of species, 128, 129;
influence on natural history, 125;
personal appearance, 125; per-
sonal history, 119; portrait, 124;
helped by his fiancee, 120; return
to Sweden, 123; and the rise of
natural history, 100-130; the Sys-
tema Naturae, 121, 125, 127; pro-
fessor in Upsala, 123; celebration
of two hundredth anniversary of
his birth, 124; as university lec-
turer, 123; wide recognition, 122;
summary on, 129-130

Lister, Sir Joseph, and antiseptic
surgery, 302; portrait, 302

Loeb, 234; on artificial fertilization,
441 ; on regulation, 440

Ludwig, in physiology, 160; por-
trait, 160

Lyell, epoch-making work in geol-
ogy, 332; letter on Darwin and
Wallace, 428-430; portrait, ^^^

Lyonet, 89; portrait and personal-
ity, 90; great monograph on in-
sect anatomy, 91; illustrations
from, 92, 93, 94, 95; extraordi-
nary quality of his sketches, 92

M

Malpighi, 58-67; activity in re-
search, 62; anatomy of plants, 66;
anatomy of the silkworm, 63;
compared with Leeuwenhoek and
Swammerdam, 87; work in em-
bryology, 66, 202; rank as embry-
ologist, 205; honors at home and
abroad, 61; personal appearance,
58; portraits, 59, 204; sketches
from his embryological treatises,
203; and the theory of pre-delinea-
tion, 203
Man, antiquity of, 366; evolution of,

365; fossil, 342, 366
Marsh, O. C, portrait, 339
Meckel, J. Fr., 162; portrait, 162
Men, of biology, 7, 8; the foremost,

437; of science, 7
Mendel, 315; alternative inherit-
ance, 317; law of, 317; purity of
the germ-cells, 317; portrait, 316;
rank of Mendel's discovery, 318,

319
Microscope, Hooke's, Fig. of, 55;
Leeuwenhoek's, 81, Figs, of, 82, 83

Microscopic observation, introduc-
tion of, 54; of Hooke, 55; Grew,
55; Ehrenberg, 106; Malpighi,
66, 67; Leeuwenhoek, 81, 84, 85,
105
Microscopists, the pioneer, 54
Middle Ages, a remolding period,

19; anatomy in, 24
Milne-Edwards, portrait, 157
Mimicry, 387

Mohl, Von, 268; portrait, 269
Miiller, Fritz, 230; O. Fr., 106
Miiller, Johannes, as anatomist, 163;
general influence, 185; influence
on physiology, 185; as a teacher,
185; his period in physiology, 184;
personality, 185; portrait, 187;
physiology after Miiller, 188

N

Nageli, portrait, 268

Naples, biological station at, 454;
picture of, 453

Natural history, of Gesner, 112, 113,
114; of Ray, 115-118; of Lin-
naeus, 1 18-130; sacred, no; rise
of scientific, 1 10-130

Natural selection, 389; discovery of,
435; Darwin and Wallace on, 437;
extension of, by Weismann, 403;
illustrations of, 390; inadequacy
of, 3Q5

Nature, continuity of, 373; return
to, 19; renewal of observation, 19

Naturphilosophie, school of, 160

Neanderthal skull, 368

Needham, experiments on sponta-
neous generation, 281

Neo-Lamarckism, 386

Newport, on insect anatomy, 100

Nineteenth century, summary of
discoveries in, 3

Nomenclature of biology, 126, 127

Nucleus, discovery of, by Brown,
243; division of, 256, 314

Observation, arrest of, 17; renewal
of, 19; in anatomy, 26; and ex-
periment the method of science,
22,39

Oken, on cells, 241; portrait, 160

Omne viv-um ex ovo, 200

Omnis cellula e cellula, 310

476

INDEX

Organic evolution, doctrine of, 347-
373; influence of, on embryology,
225; theories of, 374-414; rise of
evolutionary thought, 415-441;
sweep of the doctrine of, 372

Orthogenesis, 413

Osborn, quoted, 10, 410; in pa-
laeontology, 341

Owen, 161, 334

Palaeontology, Cuvier founds verte-
brate, 327; of the Fayum district,
343; Lamarck founder of inverte-
brate, 328; Agassiz, 334; Cope,
339; Huxley, 337; Lyefl, 332;
Marsh, 339; Osborn, 341; Owen,
334; William Smith, 330; steps
in the rise of, 331

Pander, germ-layer theory, 218

Pangenesis, Darwin's theory of, 307

Pasteur, on fermentation, 294;
spontaneous generation, 288; in-
oculation for hydrophobia, 299;
investigation of microbes, 298;
personality, 296; portrait, 295;
his su[)reme service, 299; venera-
tion of, 294

Pasteur Institute, foundation of,
299; work of, 300

Pearson, Karl, and ancestral inher-
itance, 321

Philosophie Anatomique of St. Hi-
laire, 424

Philosophie Zoologique of Lamarck,
381

Physiologus, the sacred natural his-
tory, 110-112

Physiology, of the ancients, 179;
rise of, 179-194; period of Har-
vey, 180; of Haller, 181; of J.
M tiller, 184; great influence of
Muller, 185; after MuUer, 188

Piltdown Skull, 370

Pithecanthropus erectus, 343, 369

Pliny, portrait, 16

Pouchet, on spontaneous generation,
286

Pre-delineation, theory of, 206; rise
of, Malpighi, 207, Swammerdam,
208, Wolff, 210

Pre-formation. See Pre-delineation

Primitive race of men, 366

Protoplasm, 259; discovery of, 250,
262; doctrine and sarcode, 270,

273; its movements, 261; naming

of, 269; its powers, 260
Protozoa, discovery of, 104; growth

of knowledge concerning, 104-109
Purkinje, portrait, 267

Rathke, in comparative anatomy,

163; in embryology, 223
Ray, John, 115; portrait, 116; and

species, 117
■Reaumur, 96; portrait, 98
Recapitulation theory, 230
Recent tendencies, in biology, 445;

in embryology, 232
Redi, earliest experiments on the

generation of life, 279; portrait,

280
Remak, in embryology, 223
Roesel, on insects, 95; portrait, 97
Romanes, 413

Sarcode and protoplasm, 273, 275

Scala Naturae, 131

Scale of being, 131

Schaudinn, Studies on Protozoa,
303; other contributions, 304;
portrait, 304

Schleiden, 243; contribution to the
cell-theory, 248; personality, 247;
portrait, 246

Schultze, Max, establishes the proto-
plasm doctrine, 272; in histology,
172; portrait, 273

Schulze, Franz, on spontaneous gen-
eration, 284

Schwann, and the cell-theory, 242,
244, 248, 249; in histology, 171;
and spontaneous generation, 284

Science, of the ancients, return to,
112; conditions under which it
developed, 8; biological, 4

Servetus, on circulation of the blood,

Severinus, in comparative anatomy,

143; portrait, 143
Sexual selection, 388
Shells, evolution of, 354, 355
Siebold, Von, 134, 135; portrait, 135
Silkworm, Malpighi on, 63; Pasteur

on, 299
Smith, Wm., in geology, 330
Spallanzani, experiments on genera-
tion, 282; portrait, 283

INDEX

477

Special creation, theory of, 418

Species, Ray, 117; Linnaeus, 129;
are they fixed in nature, 352; or-
igin of, 352-366 _

Spencer, 426; his views on evolution
in 1852, 427

Spontaneous generation, belief in,
278; disproved, 292; first experi-
ments on, 278; new form of the
question, 281; Redi, 279; Pas-
teur, 288; Pouchet, 286; Spallan-
zani, 282; Tyndall, 290

Steno, on fossils, 322

Straus-Diirckheim, his monograph,
96; illustrations from, loi

Suarez, and the theory of special
creation, 410

Swammerdam, his Biblia Naturae,
73; illustrations from, 74, 76;
early interest in natural history,
68; life and works, 67-77; love
of minute anatomy, 70; method of
work, 71; personality, 67; por-
trait, 69; compared with Mal-
pighi and Leeuwenhoek, 87

System, Linnaean, reform of, 130-
138

Systema Naturae, of Linnaeus, 121,
127

T

Theory, the cell-, 242; the proto-
plasm, 272; of organic evolution,
345-368; of special creation, 410

Tyndall, on spontaneous generation,
289; his apparatus for getting op-
tically pure air, 290

Type-theory, of Cuvier, 132

Uniformatism, and catastrophism,

333

V
Variation, of animals, in a state of

nature, 388; origin of, according

to Weismann, 402
Vesalius, and the overthrow of au-

thority, in science, 22-38; great
book of, 30; as court physician,
35; death, 36; force and inde-
pendence, 27; method of teaching
anatomy, 28, 29; opposition to,
34; personality, 22, 27, 30; phys-
iognomy, 30; portrait, 29; prede-
cessors of, 26; especial service
of, 37; sketches from his works,

31, 33, 34,49
Vicq d'Azyr, 146; portrait, 147
Vinci, Leonardo da, and fossils, 322
Virchow, and germinal continuity,

225; in histology, 174; portrait,

174
Vries, Hugo de, his mutation theory,
408; portrait, 409; summary of
theory, 412

W

Wallace, and Darwin, 428; his ac-
count of the conditions under
which his theory originated, 435;
portrait, 436; writings, 435

Weismann, the man, 405; quotation
from autobiography, 407; per-
sonal qualities, 405; portrait, 406;
his theory of the germ-plasm, 398-
405; summary of his theory, 411

Whitney collection of fossil horses,

357

Willoughby, his connection with
Ray, 115

Wolff, on cells, 240; his best work,
211; and epigenesis, 205; and
Haller, 211, 214; opposed by
Bonnet and Haller, 211; his pe-
riod in embryology, 205-214; per-
sonality, 214; plate from his
Theory of Generation, 209; the
Theoria Generationis, 210

Wyman, Jeffries, on spontaneous
generation, 289

Zittel, in palaeontology, 340; por:-
trait, 341

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