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Nortt) (Canilina S^tnU Hmnpraitg 



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Ji:o 9 1981 
OCT 1 9 1983 

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NOV 2 9 1989 

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With Portraits and Other Illustrations 



Professor in Northivestern Uni'versity 



Copyright, 1908, 



Published June, 1908 


Who have worked by my side in the Laboratory 

Inspired bv 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 

A. j'flf'^Af^V 



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 comimonly 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 T have attempted to bring under one view 
the broad features of biological progress, and to increase the 
human interest bv writinsj the storv 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 has 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 necessary 
will, in a measure, be compensated for by the clearness of 
the picture. References to selected books and articles have 


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 nearlv all the founders of biolos^v. 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 

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


sketch which docs 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 sufficient 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 difticulties 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, 111., April, 1908. 



The Sources of Biological Ideas Except Those of 

Organic Evolution 



An Outline of the Rise of Biology and of the Epochs ix 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 biolog}% 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, g. Science 
before his day, 9, 10. Aristotle's position in the development of 
science, II. 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- 




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. 


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, 27. His reform in the teaching of anatomy, 28. 
His physiognomy, 30. His great book (1543), 30. A descrip- 
tion of its illustrations, 30, 31. Curious conceits of the artist, 32. 
Opposition to Vesalius: curved thigh bones due to wearing tight 
trousers, the resurrection bone, 34, 35. The court physician, 35. 
Close of his life, 36. Some of his successors: Eustachius and 
Fallopius, 36. The especial service of Vesalius: he overthrew 
dependence on authority and reestablished the scientific method 
of ascertaining truth, 37, 38. 


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 li\dng 
organisms, 40. Harvey's education, 40. At Padua, comes 
under the influence of Fabricius, 41. Return to England, 42. 
His personal qualities, 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. 




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, 1 637-1680, 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 Bibli'a Natures, 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. 


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, ijoy— 
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, 



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, \\'ith 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, 



Natural history had a parallel development with comparative anatomy, 
no. The Physiologus, or sacred natural history of the Middle 
Ages, 1 10, 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, 
15 16-1565. High quality of his Historia Animalmm, 11 2-1 14. 
The scientific writings of Jonson and Aldrovandi, 114. John 
Ray the forerunner of Linnaeus, 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 Sy sterna Naturce 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 branches, 132. Alterations by Von Siebold and Leuckart, 
134-137. Tabularviewof classifications, 138. General biologi- 
cal progress from Linnasus to Darwin. Although details were 
multiplied, progress was by a series of steps, 138. Analysis 



of animals proceeded from the organism to organs, from organs 
to tissues, from tissues to cells, the elementary parts, and finally 
to protoplasm, 139-140. The physiological side had a par- 
allel development, 140. 



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. 



Bichat one of the foremost men in biological history. He carried the 
analysis of animal organization to a deeper level than Cuvier, i66. 
Buckle's estimate, i66. 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 writings, 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. 




The 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 vork, 183. Discovery 
of oxygen by Priestley in 1774, 183. Charles Bell's great discov- 
ery on the nervous system, 183. Period of Johannes Miillcr, 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. 


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 ^f 1651, 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. 



Bonnet's views on emhoitement, 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 W^olff, 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. 


The 'Cell-Theory — Schleiden. Schwann. Schultze, . . 23 


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- 



theory, 250. The cell-theory becomes harmonized with 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. \"ast importance of the cell-theory in 
advancing biology, 258. 


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 living beings, 262-275. Dujardin, 262. His 
personality, 263. Education, 263. His contributions to science, 
264. His discovery of "sarcode" in the simplest animals, in 1835, 
266. Purkinje, in 1840, uses the terin 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 lo\e of 
music and science. Founds a famous biological periodical, 272— 
274. The period from 1840 to i860 an important one for biol- 
ogy, 274. 


The Work of Pasteur, Koch, axd 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 wdth 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, 



in 1668, puts the question to experimental test and overthrows 
the beHef in the spontaneous origin of forms visible to the un- 
aided eye, 279. The problem narrowed to the origin of micro- 
scopic animalcula, 281. Needham and Buffon 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 viviim 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 qualities, 296. Filial 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- 


Heredity and Germinal Continuity — Mendel. Galton. Weis- 

MANN, 305 

The hereditary substance and the bearers of heredity, 305. The 
nature of inheritance, 305. Darwin's theory of pangenesis, 306. 
The theory of pangens replaced by that of germinal continuity, 
307. Exposition of the theory of germinal continuity, 308. The 
law of cell-succession, 309. Omnis cellula e cellula, 309. The 
continuitv of hereditary substance, 309. Early writers, 310. 



Weismann, 310. Germ-cells and body cells, 310. The hered- 
itary substance is the germ -plasm, 311. It embodies all the past 
history of protoplasm, 311. The more precise investigation of 
the material basis of inheritance, 311. The nucleus of cells, 311. 
The chromosomes, 312. The fertihzed ovnim, the starting-point 
of new organisms, 313. Behavior of the nucleus during division, 
313. The mixture of parental quahties in the chromosomes, 313. 
Prelocalized areas in the protoplasm of the egg, 314. The in- 
heritance of acquired characteristics, 314. The application of 
statistical methods and experiments to the study of heredity, 314. 
^Mendel's important discovery of alternative inheritance, 316. 
Francis Galton, 317. Carl Pearson, 318. Experiments on in- 
heritance, 318. 


The Science of Fossil Life, 320 

Extinct forms of life, 320. Strange views regarding fossils, 320. 
Freaks of nature, 321. Mystical explanations, 321. Large bones 
supposed to be those of giants, 322. Determination of the nature 
of fossils by Steno, 322. Fossil deposits ascribed to the Flood, 323. 
Mosaic deluge regarded as of universal extent, 324. The com- 
parison of fossil and living animals of great importance, 325. 
Cuvier the founder of vertebrate palaeontology, 325. Lamarck 
founds invertebrate palaeontology, 326. Lamarck's conception of 
the meaning of fossils more scientific than Cuvier's, 327. The 
arrangement of fossils in strata, 328. William Smith, 328. Sum- 
mary of the growth of the science of fossil life, 329. Fossil re- 
mains as an index to the past history of the earth, 330. Epoch- 
making work of Charles Lyell, 330. Effect of the doctrine of 
organic evolution on palaeontology, 332. Richard Owen's 
studies on fossil animals, 332. Agassiz and the parallelism be- 
tween fossil forms of life and stages in the development of 
animals, 334. Huxley's geological work, 335. Leidy, 337. Cope, 
337. Marsh, 338. Carl Zittel's writings and influence, 338. 
Henry F. Osborn, 339. Method of collecting fossils, 340. Fossil 
remains of man, 340. Discoveries in the Faylim district of 
Africa, 341. 



The Doctrine of Organic Evolution 



What Evolution Is: The Evidence upon which it Rests, etc., . 345 

Great vagueness regarding the meaning of evolution, 346. Causes for 
this, 346. The confusion of Darwinism with organic evolution, 
347. The idea that the doctrine is losing ground, 347. Scientific 
controversies on evolution relate to the factors, not to the fact, of 
evolution, 347. Nature of the c^uestion: not metaphysical, not 
theological, but historical, 348. The historical method applied 
to the study of animal life, 349. The diversity of living forms, 349. 
Are species fixed in nature ? 350. Wide variation among an- 
imals, 350. Evolutionary series: The shells of Slavonia and 
Steinheim, 351-353. Evolution of the horse, 354. The collec- 
tion of fossil horses at the American Museum of Natural Historv, 
New York, 355. The genealogy of the horse traced for more 
than two million years, 354. Connecting forms: the archaeop- 
teryx and pterodactyls, 358. The embryological record and its 
connection with evolution, 358. Clues to the past history of 
animals, 358. Rudimentary organs, 361-363. Hereditary sur- 
vivals in the human body, 363. Remains of the scaffolding for 
its building, 364. Antiquity of man, 364. Pre-human types, 365. 
Virtually three links : the Java man; the Neanderthal skull; the 
early neolithic man of Engis, 364-366. Evidences of man's evo- 
lution based on palaeontology, embryology, and archaeology, 366. 
Mental evolution, 366. Sweep of the doctrine of organic evolu- 
tion, 366-367. 


Theories of Evolution — Lamarck. D/.rwin, . . . .368 

The attempt to indicate the active factors of evolution is the source of 
the different theories, 368. The theories of Lamarck, Darwin, 
and Weismann have attracted the widest attention, 369. La- 
marck, the man, 368-374. His education, 370. Leaves priestly 
studies for the army, 370. Great bravery, 371. Physical injury 
makes it necessary for him to give up military life, 371. Por- 
trait, 373. Important work in botany, 371. Pathetic poverty 



and neglect, 372. Changes from botany to zoolog)- at the age of 
fifty years, 372. Profound influence of this change in shaping 
his ideas, 374. His theory of evolution, 374-380. First public 
announcement in iSoo, 375. His Philosophic Zoologiqiie pub- 
lished in 1809, 375. His two laws of evolution, 376. The first 
law embodies the principle of use and disuse of organs, the second 
that of heredity, 376. A simple exposition of his theory, 377. 
His employment of the word besoin, 377. Lamarck's view of 
heredity, 377. His belief in the inheritance of acquired char- 
acters, 377. His attempt to account for variation, 377. Time 
and favorable conditions the two principal means employed by 
nature, 378. SaHent points in Lamarck's theory, 378. His 
definition of species, 379. Neo-Lamarckism, 380. Darwin. His 
theory rests on three sets of facts. The central feature of his 
theory is natural selection. A'ariation, 380. Inheritance, 382. 
Those variations ^\'ill be inherited that are of advantage to the 
race, 383. Illustrations of the meaning of natural selection, 383- 
389. The struggle for existence and its consec^uences, 384. Vari- 
ous aspects of natural selection, 384. It does not always operate 
toward increasing the efficiency of an organ — short-winged 
beetles, 385. Color of animals, 386. Mimicry, 387. Sexual 
selection, 388. Inadequacy of natural selection, 389. Darwin the 
first to call attention to the inadequacy of this principle, 389. 
Confusion between the theories of Lamarck and Darwin, 390. 
Illustrations, 391. The Origin of Species published in 1859, 391. 
Other writings of Darwin, 391. 


Theories Continued — Weismann. De Vries, . , . '392 

Weismann's views have passed through various stages of remodeling, 
392. The Evolution Theory published in 1904 is the best ex- 
position of his views, 392. His theory the field for much contro- 
versy. Primarily a theory of heredity, 393. Weismann's theory 
summarized, 393. Continuity of the germ-plasm the central idea 
in Weismann's theory, 394. Complexity of the germ-plasm. Il- 
lustrations, 395. The origin of variations, 396. The union of 
two complex germ-plasms gives rise to variations, 396. His ex- 
tension of the principle of natural selection — germinal selection, 
397. The inheritance of acquired characters, 398. Weismann's 
analysis of the subject the best, 398. Illustrations, 399. The 
question still open to experimental observation, 399. Weis- 



mann's personality, 400. Quotation from his autobiography, 401. 
The mutation theory of De Vries, 402. An important contrilju- 
tion. His application of experiments commendable, 403. The 
mutation theory not a substitute for that of natural selection, 404. 
Tendency toward a reconciliation of apparently conflicting views, 
404. Summary of the salient features of the theories of Lamarck, 
of Darwin, of Weismann, and De Vries, 405. Causes for bewil- 
derment in the popular mind regarding the different forms of the 
evolution theory, 406. 


The Rise of Evolutionary Thought, 407 

Opinion before Lamarck, 407. Views of certain Fathers of the 
Church, 408. St. Augustine, 409. St. Thomas Aquinas, 409. 
The rise of the doctrine of special creation, 410. Suarez, 410. 
Effect of John Milton's writings, 411. Forerunners of Lamarck: 
Euff on^ Erasmus Dan vin, Goethe, 411. Statement of Buffon's 
views on evolution, 412^ ^ras««ts'lTarwin the greatest of La- 
marck's predecessors, 413. His writings, 414. Paley's Natural 
Theology directed against them, 414. Goethe's connection with 
evolutionary thought, 414. Causes for the neglect of Lamarck's 
theoretical writings, 415. The temporary disappearance of the 
doctrine of organic evolution, 415. Cuvier's opposition, 415. 
The debate between Cuvier and St. Hilaire, 415. Its effect, 417. 
Influence of Lyell's Principles of Geology, 418. Herbert Spen- 
cer's analysis in 1852, 419. Darwin and Wallace, 420. Circum- 
stances under which their work was laid before the Linnaan 
Society of London, 420. The letter of transmission signed by 
Lyell and Hooker, 420-422. The personality of Darwin, 422. 
Appearance, 423. His charm of manner, 423. Affectionate 
consideration at home, 424. Unexampled industry and con- 
scientiousness in the face of ill health, 424, 426. His early 
life and education, 425. Voyage of the Beagle, 425. The re- 
sults of his five years' voyage, 426. Life at Downs, 426. 
Parallelism in the thought of Darwin and Wallace, 427. 
Darwin's account of how he arrived at the conception of natural 
selection, 427. Wallace's narrative, 428. The Darwin-Wallace 
theory launched in 1858, 429. Darwin's book on The Origin of 
Species regarded by him as merely an outline, 42Q. The spread 
of the doctrine of organic evolution, 429. Huxlev one of its great 
popular exponents, 430. Haeckel, 431. After Darwin, the prob- 
lem was to explain phenomena, 433. 




Retrospect and Prospect. Present Tendencies in Biology, . 434 

Biological thought shows continuity of development, 434. Character 
of the progress — a crusade against superstition, 434. The first 
triumph of the scientific method was the overthrow of authority, 
435. The three stages of progress — descriptive, comparative, ex- 
perimental, 435. The notable books of biology and their authors, 
435-437. Recent tendencies in biology: higher standards, 437; 
improvement in the tools of science, 438; advance in methods, 
439; experimental work, 439; the growing interest in the study 
of processes, 440; experiments applied to heredity and evolution, 
to fertilization of the egg, and to animal behavior, 440, 441. Some 
tendencies in anatomical studies, 442. Cell-lineage, 442. New - 
work on the nervous system, 443. The application of biological 
facts to the benefit of mankind, 443. Technical biology, 443. 
Soil inoculation, 444. Relation of insects to the transmission of 
diseases, 444. The food of fishes, 444. The establishment and 
maintenance of biological laboratories, 444. The station at 
Naples, 444. Other stations, 446. The establishment and main- 
tenance of technical periodicals, 446. Explorations of fossil 
records, 447. The reconstructive influence of biological prog- 
ress, 448. 


I. General References, 449-451. II. Special References, 451-460. 


























Aristotle, 384-322 b.c, 

Pliny, 23-79 a.d., 

Galen, 131-200, 

Vesalius, 15 14-1565, 

Anatomical Sketch from Vesalius' Fahrica (1543), 
The Skeleton from Vesalius' Fabrica, . 
Initial Letters from the Fabrica, . 

Fallopius, 1523-1563, 

Fabricius, Harvey's Teacher, 1537-1619, 
William Harvey, 15 78-1 65 7, .... 
Scheme of the Portal Circulation according to 


Hooke's Microscope (1665), .... 

Malpighi, 1 628-1 694, 

From Malpighi's Anatomy of the Silkworm (1669), 

Swammerdam, 1 63 7-1 680, 

From Swammerdam's Biblia Natures, . . . . 

Anatomy of an Insect Dissected and Drawn by Swammerdam 

Leeuwenhoek, 1632-1723, .... 

Leeuwenhoek's Microscope, .... 

. Leeuwenhoek's Mechanism for Examining the Circulation 

of the Blood, 

, The Capillary Circulation, after Leeuwenhoek, 

Plant Cells from Leeuwenhoek's Arcana Natures, 

Lyonet, 1 707-1 789, 

Larva of the Willow Moth, from Lyonet's Monograph 


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


Central Nervous System and Nerves of the Same Animal, 

Dissection of the Head of the Larva of the Willow Moth, 

The Brain and Head Nerves of the Same Animal, . 

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

Reaumur, 1683-175 7, . , 



































Nervous System of the Cockchafer, from Straus-Du 

heim's Monograph (1828), 
Ehrexberg, 1 795-1876, 
Gesxer, 15 16-1565, 
JoHX Ray, 1628-1705, 
Lixx.Eus at Sixty (i 707-1 778), 
Karl Th. von Siebold, 
Rudolph Leuckart, . 
Severixus, 1580-1656, 
Camper, i 722-1 789, 
John Hunter, i 728-1 793, 
\'iCQ d'Azyr, 1 748-1 794, 
CuviER as a Young Man, i 769-1829, 


H. Milne-Edwards, 1800-1885, 

Lacaze-Duthiers, 1821-1901, 

Lorenzo Oken, i 779-1851, 

Richard Owen, 1804-1892, 

J. Fr. Meckel, 1781-1833, 

Karl Gegenbaur, 1826-1903, 

Bichat, 1771-1801, 

Von Koelliker, 181 7-1905, 

Rudolph Virchow, i 821-1903, 

Franz Leydig, 1821-1908 (April), 

S. Ramon y Cajal, 

Albrecht Haller, 1 708-1 777, 

Charles Bell, i 774-1842, 

Johannes Muller, i 801 -1858, 

Ludwig, 1816-1895, 

Du Bois-Reymond, 1818-1896, 

Claude Bernard, 1813-1878, 

Frontispiece of H.\rvey's Generationc Animalium (165 1) 

Selected Sketches from Malpighi's Works, 

Marcello Malpighi, 1 628-1 694, 

Plate from Wolff's Theoria Generationis (1759), 

Charles Bonnet, i 720-1 793, .... 

Karl Ernst von Baer, i 792-1876, . 

Von Baer at about Seventy Years of Agz, . 

Sketches from Von Baer's Embryological Treatise ( 

A. Kow.^levsky, 1840-1901, 

Francis M. Balfour, 1851-1882, 

OSKAR HeRTWIG in 1890, . 

WiLHELM His, 1831-1904, . 

























. 217 

1828), 221 






























The Earliest Known Picture of Cells, from Hooke's Micro- 

graphia (1665), ......... 238 

Sketch from Malpighi's Treatise on the Anatomy of Plants 

(1670), 239 

Theodor Schwann, 1810-1882, 245 

M. ScHLEiDEN, 1804-1881, 246 

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

genbaur), 255 

An Early Stage in the Development of the Egg of a Rock 

Limpet (after Conklin), 254 

Highly Magnified Tissue-Cells from the Skin of a 

MANDER (after WiLSON), 255 

Diagram of the Chief Steps in Cell-Division (after Parker), 256 
Diagram of a Cell (modified after Wilson), . . -257 

{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), 261 

Felix Duj.ardin, 1801-1860, ..... 

purkinje, 1 787-1869, 

Carl Nageli, 1817-1891, ...... 

Hugo von Mohl, 1805-1872, 

Ferdinand Cohn, i 828-1 898, ..... 
Heinrich Anton De Bary, 1831-1888, 

Max Schultze, 1825-1874, 

Francesco Redi, i 626-1697, 

Lazzaro Spallanzani, 1 729-1 799, .... 
Apparatus of Ty'ndall for Experimenting on Spontaneous 


Louis Pasteur (182 2-1 895) and His Granddaughter, 

Robert Koch, born 1843, 

Sir Joseph Lister, born 1827, 

Gregor Mendel, 1822-1884, 

Francis Galton, born 1822, 

Charles Lyell, i 797-1875, 

Professor Owen and the Extinct Fossil Bird of New Zea 


Louis Agassiz, 1807-1873, 

E. D. Cope, 1840-1897, 

O. C. M.A.RSH, 1831-1899, 

Karl von Zittel, 1839-1904, ..... 
Transmutations of Paludina (after Neumayer), 
Planorbis Shells from Steinheim (after Hyatt), . 
Bones of the Foreleg of a Horse, 














• 357 



106. Bones of Fossil Anxestors of the Horse, .... 

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 

loS. Fossil Remains of a Primitive Bird (.A.rch^opteryx), . 

loq. Gill-clefts of a Shark Compared with those of the Em- 
bryonic Chick and Rabbit, 

1 10. Jaws of an Embryonic Whale, showing Rudimentary Teeth, 362 

111. Profile Reconstructions of the Skulls of Living and of 

Fossil Men, .... 

112. Lamarck, 1744-1829, . 

113. Charles Darwin, 1809-1882, 

114. August Weismann, born 1834, 

115. Hugo de Vries, 

116. Buffon, 1 707-1 788, 

117. Erasmus Darwin, 1731-1802, 

118. Geoffroy Saint Hilaire, 1772-1844, 

119. Charles Darwin, 1809-1882, 

120. Alfred Russel Wallace, born 1823, 

121. Thomas Henry Huxley', 1825-1895, 

122. Ernst Haeckel, born 1834, 

123. The Biological Station at Naples, 

• 365 

• 381 

. 400 

• 403 

. 412 

• 413 

. 416 

• 423 


• 430 












"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 

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 



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 studv of organic chemistrv 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 laboratorv. The formation of 
living matter throudi 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 ditlercnt 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- 


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 centurv, and has continued 
in fuller measure to the present. It was the outcome of 
applying observation and experiment to the winning of new 

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. AVe 
recognize also a parallel advance in the systematic classifica- 
tion of animals and plants, and we note, furthermore, that 


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 
Avell-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 manv books about biolosjv, 
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 


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 dilTicult task of 
investigating the manifestations of life. It Avill 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 thev 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- 


acters. Only those have produced permanent results 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 

The namxs 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 biolo^jv there is relativelv 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 


world there was no science of biology as such ; nevertheless, 
the srerm 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 bv 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, wx 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 
observation 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 wxll 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 


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 })ractice, 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 
knowledge, 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 wdth Aristotle, and to 
designate him, in a relative sense, as the founder of natural 

That he w^as 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. " Ij[ayftd-i'^e4;:ta sis prepared," h e says, 
'' no models to copy. . . . Mine is t he first step, and tl 
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 Oshp rn's From th e 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 


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 earlv dav 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, Heni"y Smith Williams, pictures him 
entirely as a great classifier, and as the founder of systematic 
zoology. Whil e it is t rue that he was the found££_Qi 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 w^ork 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- 

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


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 ])hilosophical treatment of 
the structure and development of animals. Professor Osborn 
in his interesting book, From tJic Greeks to Darn'in, shows 
that Aristotle had thought oiU 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 devcloj) 
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 egg, and observed the development of 
many other animals. In embryology also, he anticipated 
Harvey in appreciating the true nature of ctevelopment as 
a process of gradual building, and not as the mere expansion 
of a previously formed germ. This doctrine, which 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 structvn-e 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 


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. 

Plertv/ig says: ''It is a matter for great regret that there 
have been preserved only parts of his three most important 
zoological works, ^Hisloria animaihuu,^ ' Dc^^^ilibiis,^ and 
^ De generaiione,^ works in which zoology is founded as a 
universal science, since anatomy and em])ryology, physiology 
and classification, find equal consideration." 

Some Errors. — Dissections were little y)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 Vjy 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 P'ulvius Ursinus (d. 1600), and was originally 
published by J. Faber. Its authenticity as a portrait is 



altcsled (1811) by \'isconli, who says that it has a perfect 
resemblance lo 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 drai)ing 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. 


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 resrarded as due mainly to that under- 
mining gossip which follows one holding prominent jjlace 
and enyiable recognition. His habits seem to haye been 
those of a diligent student with 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 tlie Elder 


(23-79 A.D.), the Roman general and litterateur (Fig. 2). 
His works on natural history, llUing thirty-seven volumes, 
have been ])reserved witli greater completeness than those of 
other ancient writers. Their overwhelming bulk seems to 
have })roduced 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 — ''a 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- 


sification of Aristotle, founded on plan of organization, by a 
highly artificial one, founded on the incidental circumstance 
of 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 tovrard spiritual 
matters, which truly seemed of higher importance. Pres- 
ently, the observation of nature came to be looked upon as 
proceeding fromx 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, 



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 x-\ges, 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- 


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 miasters of the metaphysical 
method of argument, and their mentality was by no means 
dull. \Vhile some branches of Icarnino^ might make a little 

o o 

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 mvsteries 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- 


necrs 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 was opened, but its growth 
was a slow one; a growth of which we are now to be con- 
cerned in tracing the main features. 

The Epochs in Biological History 

It will be helpful to outline the great epochs of biological 
progress 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 locked up. 

It was an epoch in biological history when Vesalius over- 
threw the authority of Galen, and studied at first hand the 
organization of the human body. 

It was an epoch when William Harvey, by adding experi- 
ment to observation, demonstrated the circulation of the 
blood and created a new physiology. The two coordinate 
branches of biology were thus early outlined. 

The introduction of the microscope, mainly through the 
labors of Grew, Hooke, Malpighi, and Leeuwxnhoek, opened 
a new world to the investigator, and the work of these men 
marks an epoch in the progress of independent inquiry. 

Linnaeus, by introducing short descriptions and uniform 
names for animals and plants, greatly advanced the subject 
of natural historv. 

Cuvier, by founding the school of comparative anatomy, 
so furthered the knowledge of the organization of animals 
that he created an epoch. 


Bichat, his great contemporary, created another by laying 
the foundation of our knowledge of the structure of animal 

Von Baer, by his studies of the development of animal 
life, supplied what was lacking in the work of (^uvier and 
Bichat and originated modern embryology. 

Haller, in the eighteenth, and Johannes Miiller in the 
nineteenth century, so added to the ground work of Harvey 
that physiology was made an independent subject and was 
established on modern lines. 

With Buffon, Erasmus Darw^in^ and Lamarck began an 
epoch in evolutionary thought w^hich had its culminating 
point in the work of Charles Darwin. 

After Cuvicr and Bichat came the establishing of the 
cell-theory, which created an epoch and influenced all 
further progress. 

Finally, through the discovery of protoplasm and the 
recognition that it is the seat of all vital activity, arrived the 
epoch 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 deep- 
lying basis of all vital manifestations. 




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 j^lant 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 fmd ourselves in^•olved 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 
obser\'ation 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 



spirits who see new trulh with clearness, and liave the bravery 
to force their thoughts on an unsympathetic pubhc. 

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 its hould have had more narrow boundaries. 
The medical 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 mainlv from brute animals. 

Galen. — The anatomist of anticjuity 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 


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- 
tiiic writers. In his writings 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 anatomv. The condition of anatom\' in the Middle Acres 
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 Vv-ere accepted as the unfailing guide to spir- 
itual truth, so Galen and other ancient writers were made 
the guides to scientific truth and thouc^ht. The baneful 
effects of this in stifling inquiry and in reducing knowledge 

Fig. 3. — Galen, 131-200. 

From Acta Medicorvm Berolinensium, 1715. 


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 ^londino, 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 bodies; and although his 
opportunities for practical study vrere 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 Sylvius (1478- 
1555), one of the teachers of Vesalius, made his mark. His 
name is preserved to-day in the fissure oj Sylvius in the brain, 
but he was not an original investigator, and he succeeded 
only in "making a reputation to which his researches do not 
entitle him." He was a selfish, avaricious man whose adop- 
tion of anatomy was not due to scientific interest, but to a 
love of gain. At the age of fifty he forsook the teaching of 
the classics for the money to be made by teaching anatomy. 
He was a blind admirer of Galen, and read his works to 
medical students without dissections, except that from time 


to time dogs were brought into the amphitheater and their 
structure exposed by unskilled barbers. 

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 ])urpose, gifted 
and forceful; and, furthermore, his work was m.arked by 
concentration and by the high moral quality of fidelity to 

Vesalius was born in Brussels on the last day of the year 
1 5 14, of an ancestry of physicians and learned men, from 
whom he inherited his leaning toward scientific pursuits. 
Early in life 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 Gunther. 

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 opj^ortunities 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 j)eriod of his career by 
Sir ^Michael Foster is so good that I can not refrain from 
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 w^ere 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- 

"Five years he thus spent in untiring labors at Padua. 

Fig. 4. — Vesalius, 1514-1564. 


Five years he wrought, not \vca\ing 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 live years, in 1542, wliile he was as yet not 
twenty-eight years of age, he was able to write the dedi- 
cation to Charles \^ 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 Hiimani Corporis Fahrica, requires some special notice; 
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 A^esalius laid the founda- 
tion of modern biological science. ]t 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 liigh 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, 

Fig. 5. — Anatomical Sketch from \''esalius's Fabrica. 
(Photograplied and reduced from the facsimile edition of 172S.) 


buildings, t-lc. The cmploymcnl of a background c\-en in 
portrait -painting was not uncommon in the same centurv, 
as in Leonardo da \'inci'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 
it an artistic pose, as is shown in Fig. 6, but nevertheless the 
bones are well drawn. Xo plates of equal merit had ap- 
peared before these; in fact, they are the earliest generallv 
known drawings in anatomy, although ^^oodcuts represent- 
ing anatomical figures were published as early as 1491 by 
John Ketham. Ketham's figures showed only externals 
and preparations for opening the body, but rude woodcuts 
representing internal anatomy and the humian skeleton had 
been published notably by Magnus Hundt, 1501; Phrysen, 
1518; and Berengarius, 1521 and 1523. Leonardo da \'inci 
and other artists had also executed anatomical drawings 
before the time of Wsalius. 

Previous to the publication of the complete work, Vesalius, 
in 1538, had published six tables of anatomy, and, in 1555, 
he brought out a new edition of the Fahrica, with slight 
additions, especially in reference to i)hysiology, which will be 
adverted to in the chapter on Harvey. 

In the original edition of 1543 the illustrations are not 
collected in the form of plates, but are distributed through 
the text, the larger ones making full-page (folio) illustrations. 
In this edition also the chapters are introduced with an initial 
letter showing curious anatomical figures in miniature, some 
of which are shown in Fig. 7. 

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



The Fahrica of A'csaliiis was a |)iccc of careful, honest 
work, the moral inlluence of which must not be overlooked. 
At anv moment in the ^\■orlc^s history, work marked bv 

sincerity exercises a wholesome 
inlluence, but at this particular 
stage of intellectual develop- 
ment such work was an inno- 
vation, 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 after- 
ward, since, at the time, his 
utterances were vigorously op- 
posed from all sides. Not only 
did the ecclesiastics contend 
that he was dissemiinating false 
and harmful doctrine, but the 
medical men from whom he 
might have expected sympathy 
and support violently opposed 

his teachings. 



Fig. 7. — Initial letters from 
Vesalius 's Fahrica oi 1543. 


were brought forward to dis- 
credit Vesalius, and to up- 
hold the authority of Galen. 
Vesalius sho^^■ed that in the 
human body the lower jaw is 
a sinde 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 curved, 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, w^hich, as every one sav;, were not cur^'ed 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- 
interf ered with by art ! " 

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 s^encrallv 
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 

The Court Physician. — The hand of the cliurch 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 
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 Naturellcs that those 
three men were the founders of modern anatomy. Vesalius 
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 

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

Eustachius, the professor of anatomy at Rome, 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 imlil 1754, and therefore did not exert the in- 
fluence upon anatomical studies that those of VesaHusdid, 

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 ])ath- 
breakers are under special limitations of being in a new- 
territory, and make more errors than they would in following 

Fig. 8. — Fallopius, 1523-1563. 

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 

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. 



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 \'esalius had so 
clearly exposed. Thus the work of Harvey was complemental 
tot hat of Vesalius, an d we may safely say that, taken together, 
the work of these two men laid thefimiidationsofjjicj Tioder n 
rnethod-of-ii^^^^&Ugat ing natu re. 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 afte^_lhe_Rxnaissance. 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 ihe^ne¥€ffi€n4s--aL-Lh£Jieart, 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^rculrilioaJii^dK^Jiu man b ody, and were prirmvnIyTor 
the use of medical men. 

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



jure, and, then, the use that the s triictiires_ _siLbservc. One 
view is essential to the other, and no investigation of animals 
and plants is comi)lcte 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 Vesnlin c; 
were not confined exclusively to structure; he made some 
experiments and some com.ments on the use of parts of the 
body, but his work was piainlv^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 vras 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 born at Folkestone, on the 
south coast of England, in 1578, the son of a prosperous 
yeoman. The Harvey family was well esteemed, and the 


father of William was at one time the mayor of Folkestone. 
Young Harvey, after five years in the King's school at Canter- 
bury, v.ent 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 tow^ard 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 ab Aqiia- 
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 u])on 
the valves of the veins. The vounsr student was taken fullv 
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 


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 having 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, i 537-1619, Harvey's Teacher. 



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- 


best portrait of Harvey, since the one painted by Janscn, 
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. 

An idea of his personal appearance may be had from the 
description of Aubrey, Vv^ho 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," 

He was less impetuous than W'salius, who had published 
his work at twenty-eight ; Harvey had demonstrated his ideas 
of the circulation in public anatomies and lectures for twche 
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 ])riorily 
of announcement, so frequently rush into print with 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 (k'alt 
with 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. 


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- 
ogy, 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 Aualomica de Mo/n Cordis et Sanguinis in 
Aninialihns, 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, 


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 

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 blo od passes froj ii 
veins_tgjul£rics_jjid moves^ irul^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 1661, and Leeuwenhoek, in 1669, to see, with the aid of 
lenses, the movement of the blood through the capiUaries 
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 w^as 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 hc_d^duced_th£xir- 
xulation frorn observations of the \;alyesJallie_vcins, 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 ])oints 


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 very 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 tlie existence of pores in the partition-wall of 
the heart through which blood could pass; and in the second 
edition (1555) of the Fahrica 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 


ebb and flow. In reference lo 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 
veins inosculate with each other, and in many places appear 

^^'^' ' ~fe2. 

1 1 V 


■ ri 

^^■iw ii 

• n i^ /J ' 



UF ^i-n-'-^x-l 

t: i 


Fig. II. — Scheme of the Portal Circulation According 

to Vesahus, 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 apj)roach to each other 
in their minute terminal twicjs, but no one before Harvev 



fullv grasped the iVlea of the movement of the blood in a 
complete circuit. 

Servetus, in his work on the Restoration of Christianity 
(Restitutio CJivistianisuii, i553)j 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 intluence 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 ^^lichael Foster seem to indicate. 

Realdus Columbus, professor of anatomy at Rome, ex- 
pressed a conception almost identical with that of Servetus, 
and as this vras 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 
1571 and 1593 similar ideas of the movement of the blood 
(probably as a matter of argument, since there is no record 


of cither 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- 
tiires on the History oj 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 defined 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 Motii Cordis) \vas 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; (l\) the arteries have 
no "pulsific power," i.e., they dilate passively, since the ])ul- 
sation of the arteries is nothing else than the im]nilse of the 
blood within them; (V) the heart is the organ of pro])ulsion 
of the blood; (\T) 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 ])assage of the blood 
peripherally from the heart makes it a physical necessity that 


most of the })lood reliirn to the heart; (VIID the blood docs 
return to the heart by way ot 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 

Harvey's Influence. — Harvey was a versatile student. 
He was a comparative anatomist as wx'll as a physiologist 
and embrvologist ; he had investigated the anatomy of about 
sixty animals and the embryology of insects as w^ell 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 prim.e 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 modern 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 Tondon. 

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


to accepting his views. In P^ngland this hostility was slight 
on account of his great personal intluence, 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 



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 (jrew in England, 
Malpighi in Italy, and Swammerdam and Lccuwcnhoek, 
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 com])ound microscope. 
Some forms of these early microscopes will be described and 
illustrated later. Although thus early introduced, micro- 




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 microsco})e entitled Micro- 
graphia, which was embellished with eight}'-three plates of 
figures. Hooke was a man of fme mental endowment, ^\■ho 
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 grood work in math- 
ematics, made many models 
for experimenting with flying 
machines, and claimed to have 
discovered gravitation 

Fig. 12. — Hooke's ^Microscope, 1665. 

From Carpenter's T/ie Microscope and Its Revelations. Permission of 

P. r.lakiston's Sons & Co. 


Newton, and also the use of a spring for regulating watches 
before Hiiygens, 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 svstematicallv bv his fellow-countrvman 
Xehemiah Grew. 

The form of th.e microscope used by Hooke is known 
through a picture and a description which he gives of it 
in his Micro graphla. Fig. 12 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 (i 628-1 711) 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 oj Plants (1673) and Anatomy oj 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 


Hookc or Grew, since that of Malpighi, Swam mere] am, and 
Leeuwenhoek was more far-reaching in its inlluence. 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 tlie 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 

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 
metamiorphosis of insects, and the internal structure of mol- 
lusks, frogs, and other animals. Leeuwenhoek is distin- 
guished for much general microsco]jic 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 little more 
closely into their lives and labors. 


Marcello Malpighi, 1628-1694 

Personal Qualities. — There arc several portraits of ^Slal- 
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 bv 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 svmpathetic 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 life 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 dignified under abuse and. considerate 
in his reply. In reference to the attacks upon his scientific 
standing, there were juiblished after his death replies to his 
critics that were written A\-hile he was smarting under their 
injustice and severity, but these replies are free from l)itterness 
and are ^^■ritten in a spirit of great moderation. The follow- 


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Fig. 13. — Malpighi, 1628-1694. 


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 1 had a 
lamentable spectacle of Alalpighi's house all in flames, 
occasioned b}" 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 methoudit I neyer 
beheld so much Christian patience and philosophy in any 
man before; for he comforted liis wife and condoled nothing: 
but the loss of his papers." 

Education. — Malpighi was born at Creyalcuore, 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 giye Marcellus, 
their eldest child, the adyantage 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 

Through the death of both parents, in i6.:|9, ^Nlalpighi 
found himself orphaned at the age of twenty-one, and as he 
was the eldest of eight children, the management of domestic 
affairs deyolyed upon him. He had as yet made no choice 
of a profession ; but, through the adyice of Natali, he resolyed, 
in 1 65 1, to study medicine. This adyice followed, in 1653, 
at the age of twenty-li^•e, he recciyed from the Uniyersity 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 Uniyersity of 
Bologna. This he did not immediately receiye, but, about 
1656, he was appointed to a post in the uniyersity, 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, 


he became associated with Borelli, who, as an older man, 
assisted him in many ways. They united in some v;ork, 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 

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 euloghim; 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 bv 
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. ?Ie 
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 1691 he was taken to Rome by the ne^vly elected pope, 
Innocent XII, as his personal physician, but under these new 


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- 
its^ations to the structure of ulants and of different animals, 
and also to their development. Entering, as he did, a new 
and unexplored territory, naturally lie 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. ]xLi66Lhe demojistrated 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 ar.e brought together in the lungs, the two 
never actuaUy in contact, but always separated by a memi- 
brane. These discoveries were first made on._thcJ.rQg, 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. 


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 mesentery. Although this antedates the similar obser- 
vations of Leeuwenhoek (1669), nevertheless the work of 
Leeuwenhoek was much more complete, and he is usuallv 
recognized in physiology as the discoverer of the capillary 
connection between arteries and veins. At this same period 
Malpighi 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 

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 jMalpighian 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 whicli 
follow have a bearing on comparative anatomy, zoology, and 

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. jNIuch skill was recjuired to 
give to the world this jMcture of minute structure. The mar- 
vels of organic architecture were being made known in i In- 
human body and the higher animals, but "no insect — lianlly, 
indeed, any animal — had then been carefull}- dcscril^ed, and 
all the methods of the work had to be discovered.'' He 


labored witli such enthusiasm in this new territor) as to throw 
himself into a fever and to set up an inflammation in the eyes. 
"Nevertheless," says ]\Ialpighi, "in performing these re- 
searches so many marvels of nature were spread before my 
eyes that 1 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. 71ie cord, which is, of 
course, the central nervous system, lie 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 

He showed also the food canal and the tubules connected 



with the intestine, which retain his name in the insect anatomy 
of to-day, under the designation of ^Iali)ighian 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 Tatin title, Disscr- 
ialio Epistolica de Bomhycc. It has been several times re- 
published, the best edition being that in French, which dates 


from ^loRtpdlicr, in 1878, and which is prefaced by an 
account of the life and labors of ?Vlalpighi. 

Anatomy of Plants. — ^.ral|)ighi's anatom.y 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, ^^"^^ 
Anaiome Plantanim occupies not less tlian 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 mcludes a treatise on galls, 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: 'VHis 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 bv Schleiden in the nineteenth centurv. 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- 
ini^-tubes of insects. But his observations on structure are 
good, and if he had accomplislied nothing more than this 
work on plants he would have a place in the history of botany. 

Work in Embryology. — Difhcult as was his task in insect 
anatomy and ]j>lant liistology, a more difficult one remains to 
be mentioned, viz., his observations of the develo])ment of 
animals. He had pushed his researches into the fmer 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- 


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 Dc Ovo Incuhato. 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 o\ er the ten folio plates without being impressed 
-with the extent and accuracy of his observations. His 
sketches are 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- 
ploved by ^lalpighi. Doubtless, much of his work was done 
with 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 belbw the surface, and essayed a deeper level of analysis 
in observinc: and describint^ 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 ^vas a different type of man — nervous, 
incisive, very intense, stubborn, and self-willed. Much of his 
character shows in the ])ortrait by Rembrandt represented 
in Fig. 15. Although its authenticity has been questioned, 
it is the only known portrait of Swammerdam. 


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 ])rivate museums. The elder 
Swammerdam had the linest 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 becam.e 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 micdicine, but for some 
reason he Avas 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. \Mien 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 by 

Fig. 15. SWAMMERDAM, 1637-1680. 


Ruysch. In 1664 he discovered the ^'alves 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 dift'erences 
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 case 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. Alost of the following passages 
are selected from that work. 

Intensity as a Worker. — He was a very intemperate 


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 tliem by drawings and suitable explanations. This being 
summer work, his daily labors began at six in the morning, 
when the sun afforded him liMit enouG^h 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 sweat under the irresistible ardors of that 
powerful luminary. And if he desisted at noon, it was onh" 
because the strength of his eyes was too much weakened bv 
the extraordinary efBux 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 w^hole days in making observations, as long as 
there was sufhcient light to make any, and whole nights in 
registering his observations, till at last he brought his treatise 
on bees to the w^ished-for perfection." 

Method of Work. — " For dissecting very minute objects, he 
had a brass table made on jjurpose by that ingenious artist, 
Samuel IMusschenbroek. To this table were fastened two 
brass arms, movable at pleasure to any part of it, and the 
up})cr 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 office of one of these arms 
was to hold the little corpuscles, and tliat of the other to ai)ply 


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 i)rocured, in regard to the exactness of the work- 
manship and the transparency of the substance. 

"But the constructing of very fme 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 e(|uably, 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 Vvas 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 Alalpighi's in regard to critical 
observation and ricliness 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- 


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 bv an examination of the Biblia Na~ 
turcB, under which title all his work was collected. His treatise 
on Bees and Mayflies and a few other articles \ycYC 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 
it embraces 410 pages of text and fifty-three plates, replete 
with figures of original observations. It "contains 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 dift'erent species of 
insects, which for that period was a very large one. There 
is, however, a considerable amount of work on other animals; 
the fine anatomy of the snail, the structure of the clam, tlie 
squid; observations on the structure and development of llie 
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 tlie 
structure of the snail. The u|)per sketch shows tlie central 
nervous system and the nerve trunks connected therev/itl"!, 
and the lower figure shows the shell and the principal muscles. 



Fig. 1 6. — From Swammerdam's Biblia A' attires. 


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

But wc should have at least one Illustration of his handling 
of insect anatomy to compare more directly with that of 
Afalpighi, already given. Yig. 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 w'orking 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. lie 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 foreg^oine 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 



In reference to the formation of animals within the egg, 
Swammcrdam was, as Malpighi, a believer in the pre-forma- 
tion theory. The basis for his position on this cjucstion will 
be set forth in the chapter on the Rise of Embn-olo,fn^\ 

There was another question in his time upon \\hich philos- 
ophers and scientiiic men were divided, which was in reference 
to the origin of hving organisms: Does lifeless matter, some- 
times, when submitted to heat and moisture, spring ijito 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 tlie possible spontaneous 
origin of life, especially among the sm.aller animals. Upon 
this question Swammierdam took a positive stand; he ranged 
himself on the side of the more scientific naturalists against 
the spontaneous formation of life. 

Antony van Leeuwenhoek (1632-1 723) 

In Leeuwenhoek we fmd 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 born 
in 1632, four years after Malpighi, and live 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 tlie 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. 


The portrait (Fig. i8) which forms a frontispiece to his 
Arcana Naturce represents him at the age cf sixty-three, 
and shows the pleasing countenance of a firm man in vigor- 
ous heahh. 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 fromi flying 
too far wild by its imagination." 

Recent Additions to His Biography. — There was asingular 
scarcitv of facts in reference to Leeuwenhoek's life until i88;, 
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 Naturce 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 Elncyclo- 
pa^dia 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- 
thousrh he sjround 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 office designated ' Chamber- 
lain of the Sheriff.' The duties of the ofiice 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, which amounted to about ;!(^26 a 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. 


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 Am.sterdam, 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 tv/ice married, but left only one child, a 
daughter by his first wife. In the old church at Delft is a 
monument erected bv this daudrter to the mcmorv of her 

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 
am^ounting to a passion. 

"That he was in com.fortable, if not afllucnt, circum- 
stances is clear from the character of his writings; that he 
was not troubled by any very 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 specimicns 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 


he began to use the microscope is not known; his first pub- 
hcation in reference to microscopic objects did not appear 
till 1673, when he was forty-one yeai's 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 
lyondon 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 povrers 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 


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

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 




Nicrstrasz 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 



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 witli 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 lit era rv 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 manv ^'^'•. ^oa. — Leemvenlioek's 
, ,, j^™, " Mechanism for Examining the 
letters. ihel^renchAcad- Circulation of the Blood. 



emy of Sciences, of which he was elected a corresponding 
member in 1697, got twenty-seven; but the hon'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 ^686 he obser ved the 
minute CLxcula.tion of-the^bleed , and demimsLmled-the ca^iil- 
Jaty connection between arteries and veins, thus forging the 

final link in the chain of 
observation showing the 
relation between these 
blood-vessels. This 
perhaps his most important 
observation for its bcarin<2j 
on physiology. It must be 
remembered that Harvey 
had nat-actiiall^L_seen the 
circulation of — tfee_blood, 
which he announced in 
1628. He assumed gn en- 
tirely sufficicni-grounds the 
existence of a cqnoplete cir- 
culation, but t here w as 

^'L^^^T^H^ Capillary Circula- ..^anting in his scheme the 
tion. (After Leeuwenhoek.) ^ 

direct-Qcubi-pniof of the 
passage of blood from arteries tojyeins. lliis was sjjjiplied 
b)L Le£jj Av en li oxik . Fig. 20^ 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 were 
progressively examined. The next advance came when he 


directed his microscope to the tail of the tadpole. Upon 
examininiij 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 toward the edges, but that each 
of the vessels had a curve or turninsr, 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 which 
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 furtherest extremities 
of its vessels, and veins Vvhen they bring it back to the heart. 
And thus it appears that an artery 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 vounsr fishes and eels. 

In connection with this it should be remembered that 
Malpighi, in 1661, observed 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 



mammals circular. He reserved ihc 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 bv Ha men, a medical student in Leyden, etc. Richard- 
son dignified him with the title 'the founder of histology,' 
but this, in view of the Avorl: of his great contemporary, 
^lalpighi, seems to me an overestimate. 

Turning his microscope in all directions, he examined 
water and found it peopled with nu'nute 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 
manv cases thev 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 
evaporatefl 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 Leeu wen- ^e made many 

hoelL's Arcana Natures.) observations on the 




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V J2^y^T' /*~V^»^r /i^v-v A"?**"^ 


Kc--^' I { f^ 

'/^"V* f '~7 i ] 1 IJj^rxj'^'^ ' ' 








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 Leeuw^enhoek represent very well the cliar- 
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 
embryo in an extreme degree, seeing in fancy the conij^lete 
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 trium^phant 
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 jjrod- 
uct. The two university-trained men showed cajmcity for 
coherent observation; they were both better able to direct 
their efforts toward some definite end; Leeuwenhoek, \\ith 
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 oi 


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

Swammcrdam 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 wandered over the vvhole 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. Through 
their efforts and that of their contemporaries of lesser note 
the new intellectual movement was now well under way. 



The work of Malpighi, Swammerdam, and Leeuwenhoek 
stimulated investis^ations 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 well 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 grev/ into amazement. Here began a new 
train of ideas, in the unexpected revelation that within the 
small compass of the body of an insect was embraced such 
a complex set of organs; a complete nervous system, tine 
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 




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

Fig. 22. — LvoNET, 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. 


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 historv\ 
Among his earliest published drawings were the figures for 
Lesser's Theology 0} Insects (1742) and for Trembley's 
famous treatise on Hydra (1744). 

His Great Monograph. — Finally Lyonet decided to branch 
out for himself, and produce a monograph on insect anatomy. 
After some ]jrelimiinary 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 Anatomiqiic de la Chenille qui ronge le hois de Saule. 
In exploring the anatomy of the form chosen, he displaved 
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 muscles 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. AMien 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 
orsrans of the bodv were all dissected and drawn with remark- 
able thoroughness. Lyonet was not trained in anatomy 



like Malpighi and Swammcrclam, but being a man of unusual 
palience and manual dexterity, he accomplished notable 
results. His great quarto volume is, however, merely a de- 
scri]Jtion of the figures, and lacks the insiglit of a trained 

anatomist. His skill as a dissector 
is far ahead of his knowledoje 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. AMien 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 extraordinarv 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 

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



Fig. 24. 

Fig. 25. 

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

Fig. 25. — Central Nervous System and Nerves of the Same. 



exhibiting the nervous gangh'a, 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 
monograj^h 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. Accordindv, Lvonet 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 



this plan, he made man}- 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 whicli he had accumulated were 
published later, but they fall far short of those illustrating 

Fig. 27. — The Brain and Head Nerves of the Same Animal. 

the Traile Anatomiqiie. Lyonet died in 1789, at the age of 

Roesel, Reaumur, and De Geer on Insect Life. — \\ e 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 tlian 


Lyonct's researches. Roesel, in Germany, Reaumur, in 
France, and De (}eer, in Sweden, were all distinguished ob- 
serv^ers in this line. Their works are voluminous and are 
well illustrated. Those of Reaumur and De Geer took the 
current French title of Menwircs pour servir a PHisioire des 
Inscctes. 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 masterlv fissures in color are fme 
examples of the art of painting in miniature. The nam.e of 
Roesel (Fig. 28) is connected also with the earliest observa- 
tions of protoplasm and with a notable publication on the 

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, ^^'hich aided in the understanding of 
that process; he invented the thermometer which bears his 
name, and did other services for the advancement of sci- 

Straus-Diirckheim's Monograph on Insect Anatomy. — 
Insect anatomy continued to attract a number of observers, 
but v/e must go forward into the nineteenth century before 
we find the subject taking a new direction and merging into 
its modern phase. The remarkable monograph of Straus- 
Dlirckheim represents the next step in the development of 
insect anatoniy 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 v/ith the 
study of articulated animals, I propose to publish a general 
work upon the comparative anatomy of that branch of the 


i.r.i.'A 'L-rti ?^v; iLrz rji 


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



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

FiG 29. — Reaumur, 1683-1757. 

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

Straus-Durckheim (1790-1865) 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 


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 ^lalpighi 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- 
siderations Generales sur rAnatomie comparee des Animaux 
Articules auxqiieUes on a joint rAnatomie Descriptive dii 
Mclolontha Vulgaris (Hajineton) donnee comme example dc 
rOrganisation des Coleopteres. 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. 


Nevertheless, the work of Straus- Durckhcim 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-Durckhcim 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 becom.e 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- 
Diirckhcim by publishing, between 1831 and 1834, researches 
upon the anatomy and physiolog}^ 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 Englishman 
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 1841, and his papers in the Philosophical Transac- 
tions of the Royal Society contain this new kind of research. 

Fig. 30. — Nervous System of the Cockchafer. (From Straus- 

Durckheim's Monograph, 1828.) 


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 
clearlv 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 territorv with enthusiasm, and throudi his 
extensive investigations all structural studies upon insects 
assumed a nevv' aspect. In 1864 appeared his Vom Ban des 
Thiei'cJien 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 


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 Alalpighi 
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 modern 
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 Phisloire des polypes (Teau 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. AVe have seen 
that Swammerdam, in the seventeenth century, had begun 
observations upon the anatomy of tadpoles, frogs, and snails, 


and also upon the minute Crustacea commonly called water- 
fleas, which are just large enough to be distinguished by the 
unaided eve. 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 (sec 
Chapter I\'). 

In addition to those essays into minute anatomy, in which 
scalpel and scissors were employed, an endeavor of more 
subtle difBculty 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 no■\^■ 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 simplest expression. 
The vital activities taking place in the bodies of higlier 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 humxan 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 held 
of experimental observation that a brief account of their 


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

Discovery of the Protozoa. — Leeuwenhoek 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 1677. It is very interesting to read 
his descriptions expressed in the archaic language of the time. 
The following quotation from a Dutch letter turned into 
English will suffice to give the flavor of liis 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 ^'iew the water with 
great attention, especially those little animals appearing to 
me ten thousand times less than those represented by Alons. 
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 observed 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 \\as roundish, 
sharpening a little towards the end, where they had a tayle, 
near four times the length of the whole bodv, 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 ihem. These litUe 
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 slook 



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 co])])er or iron wire, that ha\ing been wound 
around a stick, and unwound again, retains those vrindings 
and turnings," etc.* 

An}- one who has examined under the microscope the well- 
known bell -animalcule v;ill recognize in this first description 
of it, the stalk, and its form after contraction under the desiof- 
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 thev 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. 

0. Fr. MuUer. — 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 Dublished. This treatise bv O. Fr. jNIuiler 
was published in 1786 under the title of Animalcula Infusoria. 
The circumstance that this volume of quarto size had 367 
pages of description vrith 50 plates of sketches will gi\e som.e 
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 ('1795-1876). This scientific traveler and 
eminent observer was the author of several ^^'orks. He was 

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


one of the early observers of nerve fibres and of many other 
structures of the animal frame. Plis 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 Injiisionsthicrchcn ah 
Vollkommcne Organlsmen, 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 slowlv circulate around the sinde-celled bodv while 
they are undergoing digestion. In a fully fed animal these 
food-vacuolcs 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. Accordin«jlv he "jave to them the name '' Polv- 
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- 
tanepus 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) Avas a man of great scientific attain- 
ments, and notwithstanding the grotesqueness of some of his 
conclusions, vras 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, successfull}- combated the conclusions 
of Ehrenberg regarding the organization of the protozoa. 



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 \'on 
Siebold was adopted to the effect that these animals are each 
composed of a single cell. 

In 18.^5 Stein is engrossed in proposing names for the 
suborders of infusoria based upon the distribution of cilia 


Fig. 31. — Ehrexberg, 1795-1876. 

upon their bodies. This simple method of classification, as 
well as the names introduced bv Stein, is still in use. 

From Stein to Biitschli, one of the present authorities on 
the grou]), there were many workers, but with the studies of 
Biitschli on protozoa we enter the modern epoch. 

The importance of these animals in aft'ording a field for 
experimentation on the simplest expressions of life has 


already been indicated. Many interesting problems have 
arisen in connection with recent studies of them. The 
group embraces the very simplest manifestations of animal 
life, and the experiments 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, Caulkins and others have a bearing upon the dis- 
cussions regarding the immortality of the protozoa, an idea 
which was at one time a feature of \\ eissmann'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 
studies of Jennings on the nature of their responses to stim- 
ulations form a basis for some of the discussions on animal 



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 WTiters of classical 
antiquity were not read. Not only vrere the writings 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 envelo}) 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 Phvsiolos^us, or the Bestiarius. 
This served for nearly a thousand years as the principal 
source of thought regarding natural history. It contains 



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 givcth birth 
to cubs which remain three days without life. Then cometh 
the lion, breatheth 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 phcenix 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 
w^ould be interesting to quote them ; but that would keep us 
too long from following the rise of scientific natural histor}r 
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 BibliOr 
NaturcB, Spallanzani's Tracts, etc. 

The zoology of the Physiologus was of a much lower grade 
than any w^e 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 |)criod. The 


translation and rccopying 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 aniinals {De Difjerentiis Ani- 
maliiim). 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 somxC 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 (1516-1565), 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 ^^orks known in Latin, Greek, and Hebrew, 
either printed or in manuscript form. In the domain of 
natural history he began to look critically at animals with a 
view to describing them, and to collect with zealous care new 


observations upon their habits. His great woik on natural 
history (Historia Animalmm) 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, tVv'enty-two years after his death. The 
complete w^ork consists of about " 4,500 folio pages," profusely 
illustrated with good figures. The edition which the writer 
has before him — that of 1 585-1 604 — embraces 3,200 pages 
of text and 953 figures. 

Brooks says: "One of Gesner's greatest services 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. His friend Albrecht Diirer supplied one 
of the originals — the drawing of the rhinoceros — and it is 
interesting to note that it is by no means the best, a circum- 
stance which indicates how effectively Gesner held his en- 
graver and draughtsman up to fine work. He was also care- 
ful to mold his WTiting into graceful form, and this, combined 
with the illustrations, " made science attractive without sac- 
rificing its dignity, and thus became a great educational 

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. Ho 
could not entirely escape from old traditions. There are re- 
tained in his book pictures of the sea-serpent, the mermaids, 
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- 



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

Gesner fFig. 32) sacriliced his life to professional zeal 
during the pre\'alence of the ])lague in Zurich in 1564. 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 Animaliiim 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 


{Historia Animalhim, 1 549-1 553), and Aldrovandi, the 
Italian {Opera, 1599-1606). The former consisted of four 
folio 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 orisjinal form of the familv name was Wrav. He was 
graduated at the University of Cambridge, and became a 
fellow of Trinity College. Here he formed a friendshi]) with 
Francis Willughby, a }'oung 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 tlie view of inves- 
tigating the natural history of the places that they visited. 
On these excursions Willughby gave particular attention to 



animals and Ray to ])lants. Of Ray's several publications 
in botany, his Hisloria Plantarum in three volumes (1686- 
1704) is the most extensive. In another ^vork, as early as 
1082, he had proposed a new classification of plants, which 

Fig. 2>2,- — John Ray, 1628-1705. 

in the next century v/as 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 


his two sons, and the editing of his manuscripts. Ray per- 
formed these duties as a faithful friend and in a generous 
spirit. Pie edited and pubh'shed Wilhighby's book on birds 
(1678) and fishes (1686) with important additions of his own, 
for which he sought no credit. 

After completing his tasks as the literary executor of W'il- 
lughby, he returned in 1678 to his birthplace and continued 
his studies in natural history. In 1691 he pu])lished "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 thirtv- 
one years earlier, and which at that tim.e attracted much 
notice. He now devoted himself largely to the study of ani- 
mals, and in 1693 published a work on the cjuadrupeds and 
serpents, a work w4iich gave him higli rank in the historv 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 Rav 
Society for the publication of rare books on botany and 

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 conce])tion 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 ])ar- 
ents, thus making the term species stand for a particular kind 
of animal or plant. He noted som.e variations among sjuxies, 
and did not assign to them that unvarying and constant char- 
acter ascribed to them by Linnaeus and his follov/crs. Ray 
also made use of anatomy as the foundation for zoological 
classification, and introduced great precision anc] clearness 

^' <Sc u.. 


J ■ 


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 modern natural history. 

In Germany Klein (1685-1759) elaborated a system of 
classification embnicing 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 01 Linnaais. 

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 ever)'v/here use identical names for the same 
animals and plants. The residents of Japan, of Italy, of 


Spain, of all the Vv'orld, 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 
which 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 bv 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 
Linnceiis, 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 crovrn 
to Linn.'eus, and thereafter he was styled Carl von Linne. 

His father's resources were ^'ery limited, but he man- 
aged to send his son to school, though it must be confessed 
that young Linna?us 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, 


in 1726, he prepared to a])prcntice 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, v/here 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- 


though he lacked the necessary funds, one circumstance con- 
tributed to bring about this end: he had formed an attach- 
ment for the daughter of a weah.hy physician, named ^lore 
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 bv his own exertions, and with thirtv-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 NatiircF, 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- 


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. Clift'ort, 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 1737 brought out the Genera Plantarum,2i very original 
work, containing an analysis of all the genera of plants. He 
had previously published, besides the Sy sterna Natural, his 
Fiindarnenta Botanica, 1735, and Bihliotheca Botanica, 1736, 
and these works served to spread his fame as a botanist 
throughout Europe. 

His Wide Recognition. — An illustration of his wide rec- 
omition is afforded bv 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 without op^portunity 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 hahet.^ ' 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 aft'ec- 
tionate welcome." 


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 was 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 w^as 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 pov;er, the attendance at the university 
was greatly increased. In 1749 he had 140 students devoted 
to studies in natural history. 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 was due to other causes, but Linnaeus was the greatest 
single drawling 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 



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. — LixN^us AT Sixty, 1707-1778. 

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


Personal Appearance. — The portrait of Linnicus 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 worked 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 Linnaeus, 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, were 
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}' 

R. Hertwig says of him: "For while he in his Sy sterna 
Naturae, 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. 
Tinnffius divided the animal kins^dom into six classes — Mam- 
malia, Aves, Amphibia, Pisces, Insecta, Vermes. The fu-st 
four classes correspond to Aristotle's four groups of nnimals 
with blood. In the division of the invert ebrated animals into 
Insecta and Vermes Linnaeus stands undoubtedlv behind 


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 mutandis, couldhc 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 
animals, 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 Tin- 
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. In 
his Systema 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 uncier the common generic name of Fells y 
and gave to each a particular trivial name, or specific nam.e. 
Thus the name of the lion became Fdls Ico, of the tiger Fells 
tlgrls, of the leopard Fells pardus, of the cat Fells cat us ; and 
to these the modern zoologists have added, making the 
Canada lynx Fells Canadensis, the domestic cat Fells domes- 
iicata, etc. In a similar way, the dog-like animals v/ere 
united into a genus designated Cams, and the particular 


kinds or species became Canis lupus, the wolf, Canis vulpcs, 
the fox, Canis jamiliaris, the common dog. This sim])le 
method took the place of the varying 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 


We recognize Linnaeus 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- 
/wr<??,v/hile the botanists have adopted his Species Plantarum j 
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. Linna?us did not use the term 
familv in his formuke; 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 


To do justice, however, to the discernment of Linna?us, it 
should be added tliat hv was fully aware of the artilicial 
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. Linnccus 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 afiinities 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, f.ore odor at a incarnato.'^ 
The common rose of the forest with a flesh-colored, sweet- 
smelling tlower. In thus fixing the attention upon essential 
points he got rid of verbiage, a step that was of very great 

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 Linnieus, in his earlier 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 oric;inal stocking of the earth, one 


pair of each kind of animals was created, and thai existing 
species were the direct descendants without change of form 
or habit from the original })air. As to their number, he said : 
^^ Species tot sunt, quot jonnce ah initio creatce sunt ^' — there 
are just so many species as there were forms created in the 
beginning; and his oft-quoted remark," A'M//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, v>ithout 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 beeii sacrificed to 
the hunger of the carnivorous kinds ; but, better than making 
anv 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 Sy sterna Naturce. we find him receding from the position 
that species are fixed and constant. Nevertheless, it was 
ow^ine to liis inHuencc, more than to that of anv 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 hov/ the idea of Linna^^us in reference to the 
fixity of species gave way to accumulating evidence on tl'ie 

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 manacrement of the immense number of 



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 question in the last half of the nineteenth century. 

Reform of the Linn.ean System 

Necessity of Reform. — As indicated above, the classifica- 
tion established by LinncTUs 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 necessarv to follow different methods to bring 
natural history back into the line of true progress. The first 
modification of importance to the LinncTan system was that 
of Cuvier, who proposed a grouping of animals based upon 
a knowledge of their comparative anatomy. He declared 


that animals exhibit four types of organization, and his tvpcs 
were substituted for the primary groups of Linna_'us. 

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 tliat were generally accepted 
at the time of his writing. Between Linnaeus 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 (Seal a 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 higjher, in what was 
called a scala natiirce^^~J^7Tj^). Even so careful a \\Titer 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. Inhh System e des Animaux 
sans Vevtehres, 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. \n 
1809, in the second volume of his PJiilosopJiic Zoologicjiic, 
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 ])art, Init 
an actual pictorial representation of the relationship between 


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 liis part in founding the evolution theory, 
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 w^hich Cuvier 
held, and founded the first comiprehensive 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 combated, received but little atten- 
tion when they w^ere promulgated. We shall have occasion 
in a later chapter to speak more fully of Lamarck's contribu- 
tion to the progress of biological thought. 

Cuvier's Four Branches. — We now return to the type- 
theorv of Cuvier. By extended studies in comparative anat- 
omv, he came to the conclusion that animals are constructed 
upon four distinct plans or types: the vertebrate type; the 
molluscan 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, 


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-theory we look to his great volume on the animal 
kingdom published in ] 816. 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 Disirihue cPapres son Organisation, 181 6). 
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 182S, 
founded the science of development of animal forms. He 
arrived at substantiallv 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 

The contributions of these men proved to be a turning- 


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 followinji 
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. 

I'he 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 aflmities. 

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 ^vere 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, w^hich 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, 
v;hich have jointed appendages, into a natural group called 
Arthropoda, and uniting the segmented worms with those 



worms that Cuvicr 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 rvj}-\{ 
direction, and was destined to be carried still farther. 


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

Von Siebold fFig. 35) was an important man in the 
progress of zoology, especialh' in reference to the comparative 
anatomv of the invertebrates. 

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



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-lishes, sea-urchins, sea -cucumbers, etc., having a 
spiny skin, he designated Echinoderm.a ; the jelly-fishes, 
polyps, coral animals, etc., not possessing a true body cavity, 
were also united into a natural group, for which he proposed 
the name Coelenterata. 

From all these changes there resulted the seven primary 


divisions — branches, subkingdoms, or phyla — which, 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 n:iakes 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 tliis 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 tlie 
primary 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 



year that his essay referred to was pubb'shed (1859) appeared 
Darwin's Origin oj Species, x^gassiz, however, was never 
able to accept the idea of the transformations of species. 




(Including Crusta- 
cea, etc.) 


(Including Mol- 
lusca and all 
lower forms.) 


(Embracing five 
classes: Mam- 
malia, Aves, Rep- 
tilia, Batrachia, 



Von Siebold 


(Embracing five 





( Zoophyta. 
' Protozoa 


(Five classes.) 


\ Echinoderma 
( Coelenterata 


Steps in Biological Progress from Linn^us to Darwin 

The period from Linncens 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 w^ere being ad- 
vanced not oniv bv an accumulation of facts, but bv 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 v/ill 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. 


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 were largely dealt with, 
the habitat, the color, and the general appearance — features 
w^hich characterize the organism as a whole. Linmeus and 
Jussieu represent this phase of the work, and Buffon the 
higher type of it. ]\Iodern 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 ^^'hich 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, who, in the 
early part of the nineteenth century, founded the science of 
comiparative anatomy of animals, and in Hofmeister, who 
examined the structure of plants on a basis of broad com- 

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 twenty-one kinds of tissues by combinations of 
w'hich the organs are com.posed. This step laid the founda- 
tion for the science of histolosjv, or minute anatomv. Bichat 
called it general anatomv {Anatomic Cenerale, 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 niagnifying-lenses were greatly impro\'ed — 
it was a product of a closer scrutiny of nature with im])roved 
instrumicnts. The foundation of the work, especially for 
plants, had been laid by Leeuwenhoek, Malpighi, and (}rew. 


But ^^■hcn the broad generalization, that all the tissues of 
animals and plants arc 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 

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 Naturce, 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 Linnceus, 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 

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




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 anatom.y 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 tliis 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 Plarvey, 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 v\'as 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 merelv the bonv 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 




comparative anatomy there gradually emerged naturalists 
who com.pared 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 


Zootomia Democritce. The title was derived from the Roman 
naturalist Democrita?us, and the date of its publication, 16^5, 
places the treatise earlier than the works of Malpighi, Leeu- 
wenhoek, and Swammerdam. The book is illustrated bv 
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 u]) to Cu\'ier. 

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

Cam.per, whose portrait is shown in Fig. 2>^y 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 Boerhaave 
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 follow his ov/n tastes. He travelled exten- 
sivelv and gathered a larcre 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. Perliaps the possession of riches was one of 
his limitations; at any rate, he lacked fixity of i)urpose. 

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



The latter point is of interest, as antedating the condiisions 
of Cuvicr regarding the nature of fossil bones. Camper also 
made observations u])on the facial angle as an index of in- 
telliorence in the different races of mankind, and in lower 

Fig. 38. — Camper, 1722-1789. 

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 w^ent 
directly to nature for his facts; and, although he made errors 
from which he would have been saved by a wider acquaint- 



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 older brother, William, a man of more elegance and 
refinement, who well understood the value of polish in refer- 



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Fig. 39. — John Hunter, 1728-1793. 

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 refmements of taste and manner of 
which his brother was a good example. '' \Miy," the doughty 
John is reported to have said, '' they wanted I0 make me study 


Greek! Thcv tried to make an old woman of me!" How- 
ever much lack of a|)])reciation this attitude indicated, it 
shows also the Philistine independence of his spirit. This 
mdependence of mind is one of his striking characteristics. 

This is not the place to dwell upon the unfortunate con- 
trcvcrsv that arose between these two illustrious brothers 
reirardinsf scientific discoveries claimed bv each. The r^osi- 
tion of both is secure in the historical development of medicine 
and surgery. Althoudi the work of John Hunter was 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 w^as his object to preserve specimens to illus- 
trate the phenomena of life in all organisms, w^hether 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 m.uch in bringing this collection together and leaving 
it to posterity that he ad^^anced comparative anatomy as in 
wdiat 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 (Fig. 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 m.edicine, remaining in the metropolis to the time of 
his death in 1 794. He was celebrated as a physician, became 



permanent secretary of the nevvlv 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- 
^•anced 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 Academy. 

Fig. 40. — VicQ d'Azyr, 1748-1794. 

He made extensiye studies upon the organization particu- 
larly of birds and quadrupeds, making comparisons bet\yeen 
their structure, and bringing out ne\y points that \yere 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 seryed to mark the beginning 
of a new kind of precise comparison. These were not merely 
fanciful comparisons, but exact ones — part for part; and 
his general considerations based upon these comparisons were 
of a brilliant character. 


As Huxlev has said, "he mav be considered as the founder 
of the modern science of anatomv." 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 Vv'ith any particular degree of accuracy the 
course of fiber tracks 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 defmitely to the progress of 
natural science, he found vast accumulations of separate 
mxonographs 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'Ayzr 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 

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 


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 u[)on 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 who 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 observa- 
tions are discoveries I will then believe you." 

Birth and Early Education. — Cuvier was born in 1769, 
at Montbeliard, a village at that time belonging to Wiirttem- 
berg, but now a part of the French Jura. His father was a 
retired military officer of the Swiss army, and the family, 
being Protestants, had moved to Alontbeliard 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 knowledge of 
Latin. Pie earlv showed a leanin<j toward natural historv; 
having access to the v/orks of Oesner and ButTon, he profited 
by reading these two writers. So great was his interest that 


he colored the plates in Buffon's Xaliiral 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 Wiirttemberg, 
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 hidi rank as a student. Here he met Kielm.ever, a 
young instructor only four years older tlian himself, who 
shared his taste for natural history and, besides this, intro- 
duced him to anatomy. In after-years Cuvier acknowledged 
the assistance of Kielmever 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- 
m.ent 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 tlie sea-coast in Normandy, 
near Caen. For six years (1788-1794) he lived in this noble 
familv, v/ith much time at his disposal. For Cuvier this 
period, from the age of nineteen to twenty-five, ^^■as 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 strucure 
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 


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 was 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 
Cuvier 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 
collected, 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 



SO that he was called to occupy prominent offices under the 
government, and he came ultimately 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 very interesting to note in his 
portraits the change in his physiognomy accompanying his 
transformation from a young man of provincial appearance 

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

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, young 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 coimtenance after 



his wide recognition passing by a gradation of steps from the 
position of liead 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 


lost his love for natural science, ^^'ith 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 everything 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- 
racierise parlout M. Cuvier, c'est Vesprit vaste.^^ Plis 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 
^^"orked; 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 


founded comparative anatomy. From 1801 to 1805 appeared 
his Legons (T Anatomle 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 pakeontology. 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^apves 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 dift'erence^ 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 w^ith w^hich he was engaged. In his lecture^ 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 m tlie midst of exacting cares he found 
time to V;ind his family in love and devotion. Cuvier was 
called upon to suffer ])oignant grief in the loss of his chil- 
dren, and his direct familv was not continued. He \\as 
especially broken by the death of his daughter who had 
grown to young womanhood and was about to be married. 


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 Shortcommgs. — Nevertheless, there are certain 
things in the life of Cuvier that we \\ish mJght not have been. 
His break with liis old friends Lamarck and Saint-Hilaire 
seems to show a domination of qualities that were not s^en- 

1 o 

erous and kindh-; 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 Evolution. 

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 centurv, 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 Cu\ ier, was the last 
country slov/ly and reluctantly to harbor as true the ideas 
regard in o^ 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 


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 anaiomy 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 

Milne-Edwards. — H. ^lilne-Edwards (1800-1885) was a 
man of great industry and fine attainments; prominent alike 
in comparative anatomy, comparative physiology, and general 
zoology, prof essor for many years at the Sorbonne in Paris. 


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 v/ork on 
comparative anatomy took the form of explanations of the 
activities of animals, or coniparati\ e physiology. His com- 
prehensive treatise Legons sur la Physiologie et rAnatomie 
Comparec, in fourteen volumes, 1857-1881, is a mine of 
information regarding comparative anatomy as veil as the 
physiologv 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. 4^ , 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 vear in England. He spent 
some time at the Jardin des Plantes examining the extensive 
collections in the museum. iVlthough 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 Owen. Although he never studied 
under Cuvier, in a sense he may be regarded as his disciple. 
Owen introduced into anatomy the imiportant 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 



the wing of a bat and the foreleg of a dog. Analogy 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 



anatomy of vertebrates (i 866-68). 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 Natiir philosophic. 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 



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, 1804-1S92. 

as lo the main facts of comparative anatomy mark him as 
one of the leaders in this lield of research. The inlluence 
of Huxley as a i)opular exponent of science is dealt with 
in a later chapter. 


1 62 

bi()L()(tV axd its makers 

Meckel. Just as C\ivic-r stands at the beginning of the 
school of comparative anatomy in France, so does J. Fr. 
Meckel in Cermany. Meckel (i 781-1833) was a man of 
rare talent, descended from a family of distinguished anat- 
omists. From i8o_| to 1806 he studied in Paris under Cuvier, 
and wlun lie came to leave the French capital to become 
j)rofessor of anatomy at TTalle, he carried into Germany the 

Fig. 47. — J. Fr. Meckel, 1781-1833. 

teachini^s and methods of his master. He was a strong? force 
in tlie 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 laboratorv a 
number of investigations that were published in a periodical 
which he founded. "Meckel himself produced many scientific 
jjapers and works on comparative anatomy, which assisted 


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 imj)ortance of elucidating anatomy with researches 
in development. 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 Baer on there moval of the latter to St. Petersbun^. 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 (i 801-1858), 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- 
omy with their researches upon functional activities. (For 
Mliller's portrait sec 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 struc- 



luri', to which were added the ideas derived from the study of 
tlu' dexelo] mwni of orL,^ans. He was endowed with an intensely 
keen insight, an insi,L,^ht which enabled him to separate from 
tlie vast mass of facts the important and essential features, 
so that tliev vielded 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- 


E. D. Cope. — In America the greatest comparative 
anatomist was E. D. Cope (i 840-1 897), a man of the highest 
order of attainment, who deak 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 comparative 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. Comiparative 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. 



We must recognize Bichat as one of the foremost men in 
biological history, 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 comj^rehensive 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 

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- 



tation is steadily advancing as our knov.'lcdge advances; 
who, if we compare the shortness of his hfe 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, 1 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 Lvons 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, 


who was gifted v;iih a po\\crful memory, volunteered without 
previous notice to take his place. The lecture was a long and 
difficult one on llie fractures of the clavicle, but Bichat's 
abstract was so clear, forceful, and comj)lete that its delivery 
in well-chosen language produced a great sensation both upon 
the instructor and the students. This notable performance 
served to brinij 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 ])rinter 
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 w^as 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 own, 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 jjortrait 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, w^hich were 
open and free." 

His Phenomenal Industry.— His industry was phenom- 



cnal; besides doing the work of a professor, he attended to 
a considerable practice, and during a single Vvinter 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 \A"as 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 ujjon them, but from the 


inlcnsily 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 
Mrmhrams); followed quickly by his Physiological Re- 
searches into the I^henomena of Life and Death {Recherches 
Plivsiologiqucs siir la Me el la Mart); then appeared his 
General Anatomy {Anatomie Generalc) in 1801, and his trea- 
tise upon Descriptive Anatomy, upon which he was working 
at the time of his death. 

PTis death occurred in i8ci, and was due partly to an 
accident. Pie 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 w'ork was to set the w^orld 
studying the minute structure of the tissues, a consequence 
of which led to the modern studv of histologv. 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 w^hich 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 


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, Mrchov/, 
Leydig, and Ramon y Cajal, w^hose researches stand in the 
direct Hnc of development of the ideas promulgated by 

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 tlioroughly investigated 
from other points of view. The cell-theory, which took rise 
in 1839, was itself epoch-making, and the science of general 
anatomy w^as 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 ccll-theorv. Had not the life of Bichat 
been cut off in his earlv manhood, he miirht well have lived 
to see this great discovery added to his own. 

Koelliker. — Albrccht 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 scicntilic 
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. 


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


In 1S47 he was called to the University of Wurzburg, 
where he remained to the time of his death. From 1850 to 
iQoo, scarcely a year passed without some important contri- 
bution from \'on Koelliker extending the knowledge of his- 
tologv. His famous text-book on the structure of the tissues 
{tlandbuch dcr Geivebclehre) joassed through six editions from 
1852 to 1893, ^^^^ ^'^"'^^^ edition of it being worked over and 
brought up to date b}- 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 com])letely over the ground of the vast accumulation of 
information rerardinsr the nervous svstem which an armv 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 ^lax 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 service 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 }:)hases: 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, 1S17-1905. 



been extensively cultivated, and the development of patho- 
logical studv has .greatly extended the knowledge of the 
tissues and has had its intluencc upon the progress of normal 
histologv. Goodsir, in England, and Henle, in (jermany, 
entered the field of ])athological histology, both doing work 

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

of historical importance. They were soon followed b\' \'ir- 
chow, whose eminence as a man and a scientist has made 
his name familiar to ])coijle in general. 

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



parliament. He assisted in molding the cell-theory into 
better form, and in 1858 jjublished a work on Cellular 
PatJwlogy, which applic^l 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, 1821-190S (April). 
Courtesy of Dr. Wm. M. Wheeler. 

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

Leydig. — Franz Leydig (Fig. 52) was early in the field 
as a histologist with his handbook (LcJirbuch dcr Hisiologie 



des Mcnschcn iiiid dcr Thierc) published in 1857. He applied 
histology especially lo ihc tissues of insects in 1864 and sub- 
sequent vears, an account of which has already been given 
in Chai)ter \'. 

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, 1S50- 

field of research is of world-wide renown. His investiirations 
into the microsco])ic texture of the nervous svstem and sense- 
organs have in large part cleared up the questions of the com- 
plicated relations between tlie 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- 


versary of that university. Besides receiving many honors in 
previous years, in 1906 he was awarded, in conjunction with 
the Itahan 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; Koelliker, as the typical 
histologist after the analysis of tissues into their elementary 
parts; Mrchow, 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 

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 inllammations, of 
the action of phagocytes, and of all manner of abnormal 

In attempting to trace the beginning of a delinite founda- 


tion for the work on the structure of tissues, we go back to 
Hichat rather than to Leeuwenhoek, as Richardson has pro- 
jjosed. I^ichat was the first to give a scientific basis for 
histology founded on extensive observations, since all earlier 
obser\ers gave only separated accounts of the structure of 
particular tissues. 


Harvey Haller Johannes Muller 

Physiology had a parallel devdopment with anatom}-, 
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 w^hat 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 mav 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 
carry 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 s])irit. 
This went under the name pncuma, and the pneuma-theory 
held sway until the period of the Revival of Learning. 



Among the ancient ])hysiologists the great Roman phy- 
sician Cialen is the most noteworthy figure. As he was the 
greatest anatomist, so he was also the greatest physiologist 
of ancient times. All ])hysiological knowledge of the time 
centered in his writings, 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 (i 578-1657). In his 
time the old idea of spirits and humiors was gi\ingway, 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 ca])illarics 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 w^as 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 ?larvey'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- 


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 modern 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 Harv^ey's time we pass to the 
period of Haller (1708-1777), 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 learning, and to him was applied 
by unsympathetic critics the title of " that abyss of learning." 
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 Verworn 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- 

I I P~ -^ A ;:3V 



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 708-1777. 

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. 


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 w^ork referred to is his Elements of Ph\si- 
ology {Elemcnta PhysiologicB 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 Miiller 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 fibers of the anterior 
roots of the spinal cord belong to the motor type, while those 
of the posterior roots belong to the sensory type. 

This great truth w^as 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 oj a 
New Anatomy oj the Brain, which was printed for jjrivate 
distribution. It was expanded in his papers, beginning in 
182 1, 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 Miiller had reached the age of twenty- 

1 84 


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 
])rivate life he was distinguished by '' unpretending amenity, 
and simplicity of manners and deportment." 

Fig. 55. — Charles Bell, 1774-1842. 

Period of Johannes MuUer. — The period that marks the 
beginning of modern physiology came next, and was due to 
the genius and force of Johannes Mliller (1801-1858). Ver- 
wom says of him: "He is one of those monumental fig- 
ures that the history of ever}' science brings forth but once. 


They change the whole aspect of the field in which they work, 
and all later growth is influenced by their labors." Johannes 
Muller 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 
Muller, 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 fmd 
"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, Miiller trained many gifted young men, among whom 
w^ere Ludwig (1816-1895), Du Bois-Reymond (1818-1896), 
and Helmholtz (1821-1894), who became distinguished 
scholars and professors in German universities. Helmholtz, 
speaking of Miiller's influence on students, paid this tribute 
to the grandeur of his teacher: "Whoever comes into contact 
with men of the flrst rank has an altered scale of \alues in life. 
Such intellectual contact is the most interesting event that 
life can offer." 

The particular service of Johannes Muller to science was 


to make physiology broadly comparative. So comprehensive 
was his gras]) ii])on the subject that he gained for himself 
the tide of the greatest physiologist of modern times. He 
brought together in his great work on the physiology of man 
not onlv all that had been previously made known, carefully 
sifted and digested, l)ut 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 Handhuch der Physiologie 
des MenscJien: "This work stands to-day unsurpassed in 
the genuinely philoso])hical 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 

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 (juality. In physiology he stood on 
broader lines than had ever been used before. He employed 
ever}' means at his command — experimenting, the observa- 
tion of sim})le animals, the microscope, the discoveries in 
])hysics, in chemistry, and in psycholog}\ 

He also introduced into physiology the principles 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. 

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

Fig. 56. — Johannes Mullkr, iSoi -1858. 



but his inllucncL' was i)rolon<^cd through the teachings of his 

Physiology after Muller 

Ludwig. — Among the men who handed on the torch of 
Muller there has already been mentioned Ludwig (Fig. 



Fig. 57. — LuDwiCx, 1816-1895. 

57). For many years he lectured in the University of 
Lcipsic, attracting to that university high-minded, eager, 



and gifted young men, who received from this great lumi- 
nary of physiology by expression what he himself had de- 
rived from contact with Alliller. There are to-day dis- 
tributed through the universities a number of young 

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

physiologists who stand only one generation removed from 
Johannes Aliiller, and w^ho still labor in the spirit that was 
introduced into this department of study by that great master. 
Du Bois-Reymond.— Du Bois-Rcymond (Fig. $8), an- 
other of his distinguished pupils, came to occupy the chair 


which Miiller himself had filled in the University of Berlin, 
and during die period of his vigor was in physiology one of 
the liirhls of the world. It is no uncommon thino^ to find 
recently published ])hysiologies dedicated cither to the mem- 
or)' of Johannes Miiller, 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. 
P>om this disposition among physiologists to do homage to 
Miiller, we are able to estimate somewhat f»ore closely the 
tremendous reach of his influence. 

Bernard. — \Mien 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 w'ithin the human body. But besides his 
technical researches, any special consideration of which lies 
(juite beyond the purpose of this book, he published in 1878- 
1879 ^ 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 ve get aux. 

The thoughtful face of Bernard is shown in his portrait, 




59. He was one of those retiring, silent men whose 
natures are difficidt to fathom, and who are so frequently 
misunderstood. A domestic infelicity, that led to the se])ara- 
tion of himself from his family, added to his isolation and 
loneliness. When touched by the social s])irit he charmed 

Fig. 59. — Claude Bernard, 1813-1S78. 

people by his personality. He was admired b}- llie 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 

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


presence, with a nc^ble head, ihe eyes full at once of thought 
and kin(hiess, he drew llie look of observers upon him wher- 
ever lie api)eare(L As he walked in llie streets passers-by 
mij^ht be heard to say' I wonder who that is; he must be 
some dislin,u;uished man.' " 

Two Directions of Growth. — Physiology, established on 
the broad foundations of M tiller, developed along two inde- 
})endent pathways, the physical and the chemical. We find 
a group of physiologists, among whom Weber, Ludwig, 
Du Hois-Revmond, and Helmholtz were noteworthy leaders, 
devoted to the investigations of physiological facts through 
the application of measuremicnts and records made by ma- 
chinery. \\ iih 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 \arious forms of stimulation, the rate of transmiission 
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 physiology. As might have been 
j^redicted, 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 ojjportunity to study at leisure phenomena 
that occu])y a very brief time. 

Tlie other marked line of physiological investigation has 
been in the domain of chemistr}% where W^ohler, Liebig, 
Kiihne, 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 observers have also made a particular feature of 


the study of the chemical changes going on within the living 

The union of these two chief tendencies into the physico- 
chemical aspects of physiology has established the modern 
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. A\[ 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 imm.ediate successors of Haller became 
not only highly speculative, but highly mystical, tending to 
obscure anv close analvsis of vital activitv 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 ]Muller's work 
there has been built up the modern 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 morpholog}- in the 
work which is being so assiduously carried on to-day under 
the title of experimental morphology. 

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


spoken of, we may associate with them the names of Sir 
^lichael Foster and Burdon-Sanderson, in England; and of 
Briicke (one of Miiller'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. 



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." 

Embryology 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- 



mcnlarv 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 bv means of which phases in the evolution of animal 
life may be (k'ci{)hered. 

Bearing in mind the continually shifting changes through 
which animals pass in their embryonic developmicnt, 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. H, 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 
\'on 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 Period of Harvey and AIalpighi 

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

The embryological work of \\'olff's great predecessors, 
Harvey 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 ^lalpighi, in 
his native town of Crevalcuore, in 1894, gives him well- 
merited recognition as the founder of embryology, and the 
late Sir Alichael Foster has written in a similar vein in his 
delightful Lectures on the History of 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 vrork is more philoso]:)hical; 
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 
moderns. 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 


lived, Malpighi could so successfully curb the tendency to 
induli^a' in \\ordy disquisitions, and that he was satisfied to 
obscn-e carefully, and tell his story in a simple way. This 
(jualitv of mind is rare. As Emerson has said: ''I am im- 
pressed with the fact that the greatest thing a human soul 
e\er does in this world is to see something, and tell what it 
siiw 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 clearlv 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 Hanxy's time. The reason 
for this will 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- 
\ances 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. 


By clearly teaching, on the basis of his own observations, 
the gradual formation of the bo(l\- by aggregation of its jjarts, 
he anticipated Wolff. This doctrine came to be known under 
the title of "epigcnesis," but Harvey's epigenesis* was not, 
as Wolff's was, directed against a theory of i)re-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 wliich 
surrounded the work of Wolff in the next century. Had the 
doctrine of pre-formation been current in Harvey's timic, we 
are quite justified in assuming that he would have assailed it 
as vigorously as did Wolff. 

His Treatise on Generation. — Harvey's embryological 
work was published in 165 1 under the title Exercitationes de 
General ione 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 miany deer killed in the park, at intervals, 
in order to give Harvey the opportunity to study their devel- 

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 ])ar- 

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 front England to Italy, as 
already recounted, he came under the instruction of Vd- 
bricius in Padua. In 160c, Fabricius ])ublished sketches 
showing the development of animals; and, again, in i()25, 
six years after his deatli, appeared his illustrated treatise on 

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


llu- (li'vilopnuiil of ihc cliick. Kxccpl the figures of Coiler 
(1573)' tliosc of I'\il)riciiis were the earliest published illus- 
Iralions of the kind. Altogether liis ligures show develop- 
mental stages of the cow, sheep, pig, galeiis, serpent, rat, and 


Harvev's own treatise was not illustrated. With that 
singular independence of mind for which he was conspicuous, 
the vision of the puj^il 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 |)lastic force breaks forth and germinates. This first 
commencement of the chick, however, so far as I am aware, 
has not vet been observed by any one." 

It is to be understood, however, that the descriptive part 
of his treatise is relatixely brief (about 40 jxiges 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 develojjment. 

The aphorism, " onnic viviun ex ovo,'' though not invented 
by Har\ey, was brought into general use through his writings. 
As used in his da}-, howe\er, it did not ha\e its full modern 
significance. With Harvey it meant sim])ly that the embryos 
of all animals, the viviparous as well as the oviparous, orig- 

TlWWTO iiil W Illi Uyf 

i "r-^ 



Ciuliclmiis Harvciii^ 

Ac t 

vjC!icratK)ne Ammaliuiu. 

Fig. 6o.— Frontispiece to Harvey's Gcncrationc Animalinm (1651). 


natc in t'L,^i^'s, and it was directed against certain contrary 
medical llieories of the time. 

The lir>t edition of his Gcncratione Animalium, London, 
1651, is ])rovided 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 
inscri])tion " ex ovo omnia,^^ and from the box issue all forms 
of living creatures, including also man. 

Malpighi. — The obser\er in embryology who looms into 
prominence between Harvey and Wolff is Malpighi. He 
su])plied 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 
PiiUi in Ovo and De Ovo Incubate. 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 descrii)tions, a marked contrast to the 350 pages of Harvey 
unjjrovided with illustrations. 

His pictures, although not correct in all particulars, repre- 
sent what he was able to see, and are ver\' 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 transitor}^ 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). 



vesicles and eye-pockets. His delineation of heart, brain, 
and e}C-vesicles are far ahead of those illustrating Wolff's 
Theoria Gcncyationis, made nearly a hundred years later. 

Fig. 6 1 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 Incubafo, still in pos- 
session of theRoyal 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 


of the embryo to pre-exist within the egg. He thought that, 
possibly, the blood-vessels were in the form of tubes, closely 
wrapped 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 liis 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 centuiy. 
For this reason we may speak of him as the founder of 

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 cpigenesis. 


As \vi' ha\c rilrauly scx-n, Hancy, more than a century before 
the ])iil)licalions of Wolff, had clearly taught that develop- 
ment is a ])rocess of gradual becoming. Nevertheless, Wolff's 
work, as opposed to the new theory, was very important. 

While the facts fail to supi)ort the contention that he was 
the founder of epigenesis, it is to be remembered that he has 
claims in olher directions to rank as the foremost student of 
embrvology ])rior to \'on Baer. 

As a i)reliminary to discussing Wolff's position, we should 
bring under consideration the doctrine of pre-formation and 

Rise of the Theory of Pre-delineation. — The idea of pre- 
formation in its first form is easily set forth. Just as when 
wc 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 fiower-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 de\'elopment 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 cvolulion, giving to 
that term (|uite 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. Altliougli 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 


Bonnet, Haller, and Leibnitz were among its founders. This 
implication is in part fostered by the circumstance that 
Swammerdam's Biblia NatiircB^ wliich contains the germ of 
the theory, was not published until 1737 — more than half a 
century after his death — although the observations for it were 
completed before ^lalpighi'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 obser\ation, is accepted 
as establishing the period of emergence of ideas, there were 
other men, as ^lalpighi 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 whicli 
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 thev were lacerated bva li^rht stroke. Therefore, 
it is right to confess that the beginnings of the chick pre-exist 
in the egg, and have reached a higher develo])ment in no other 
way than in the eggs of plants." (" Quare pulli slamiua in ovo 
prcBexisterc, altioremque originem nacta esse fateri convenit, 
baud dispari ritu, ac in Plantarum ovis.") 


Swanimcrdam (1637-1680) supplied a somewhat belter 
basis, lie obser\e(! that the jxirls of the butterlly, and other 
insects as well, are discernible in tlie chrysalis stage. Also, 
on observing ealer])illars 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 LX])ansion of already formed parts. 

A new feature was introduced through the disco\'erv, bv 
Lceuwenhoek, about 1677,* of the fertilizing filaments of 
eggs. Soon after, controversies began to arise as to whether 
the embryo ])re-cxisted in the sperm or in the egg. By 
Lceuwenhoek, Hartsoeker, and others the egg was looked 
upon as sin"i])ly a nidus within which the sperm developed, 
and they asserted that the future animal existed in miniature 
in the sperni. 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 

It is interesting to follow the metaphysical speculations 
vs'hich 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 
consecjuence 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 cmhottcment, 
which was so greatly elaborated by Bonnet and, by Leibnitz, 
apyjlied to the development of the soul. Even Swammerdam 
(who, b}- the way, though a masterly observer, was always 
a |)Oor 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. 

>, xii^iiSi^.'- 




\ '■ •# 


^'"^ •~^Aw>«JL<, 


/- .zi/ 'fJ <" ••^''•' 






Fig. 63. — Plate from Wolff's 77;rcr /a Gcncratiouis (1759), Sliowing 
Stages in the Development of the Chick. 


ceivcd of by him as a ncccssily, when the last germ of this 
wonderful series had been unfolded. 

His successors, in efforts to compute the number of 
homunculi wliich 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-formalion and encasement in his Thcoria 
Gcficnilionis, published in 1759. This consists of three 
jxirls: one devoted to the development of plants, one to the 
develoi)ment 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 arc shown in Fig. 63, are not, on the \\hole, 
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 
develo])ment, a comparison of the two men's work is favor- 
able to Malpighi. The latter shows much better, in corre- 
sj)onding stages, the series of cerebral vesicles and their rela- 
tion to the optic vesicles. Moreover, in the wider range of 
his work, hie 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 "Wolflmn bodies," of which he was the 

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 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 1768 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 which 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 Wolff's work was 
launched into an uncongenial atmosphere. The great physi- 
ologist Haller could not accept the idea of e])igenesis, but 
opposed it energetically, and so great was his authority that 
the views of Wolff gained no currency. This retarded 
progress in the science of animal development for more tlian 
a half-centurv. 

Bonnet was also a prolific writer in opposition to the ideas 
of Wolff, and w^e should perhaps have a ]:>ortrait of him 
(Fig. 64) as one of the philosophical naturalists of the linu-. 
His prominent connection with the theory of pre-delineation 

* Be Formatione Intestinorum, Nova Commeutar, Ac. Sci. Pclrop., 
St. Petersburg, XII., 1768; XIII., 1769. 



in its less grotesque form, his discovery of the development 
of the eggs of jjlant-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, i 720-1 793. 

naturalists of the period. His system of philosoph}', which 
has been carefully analyzed by Whitman, is designated by 
that writer as a svstem of negations. 

In 1 82 1, J. Fr. ^Meckel, recognizing the great value of 


^^'olff's researches on the development of the intestines, 
rescued the work from neglect and obscurity bv publishing 
a German translation of the same, and bringing it to the 
attention of scholars. From that time onward Wolffs labor 
was fruitful. 

His De Formatione Inlcstinonim rather than his Thcoria 
Gcncvationis 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 cmbrvo, 
which, under Pander and \^on 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 ner\ous 
svstem arises first from a leaf-like laver, and is follo\ved, 
successively, bv a flesh laver, the vascular svstem, and lastlv, 
by the intestinal canal — all arising from original leaf-like 

In these important generalizations, although thev are 
verbally incorrect, he reached the truth as nearly as it was 
possible at the tim_e, and laid the foundation of the germ- 
layer theory. 

Wolff was a man of great power as an observer, and al- 
though his influence was for a long time retarded, he should 
be recomized as the foremost investigator in embrvoloirv 
before \on Baer. 

Few Biographical Facts. — Tlie 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 tlie 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. 


It has been impossible lo discover a portrait of Wolff, 
alihough J have sought one in various ways for several years. 
The sccrctarv of the Academy of Sciences at St. Petersburg 
writes that no portrait of AVolff exists there, and that the 
Acadeni\- will gratefuU}' receive information from any source 
regarding the existence of a portrait of the great acade- 

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 A 1 tiller was for physiology, von Baer 
was for embryology; all subsequent growth was influenced 
by his investigations. 

The greatest classic in embryology is his Development oj 
Animals (Eniwickelungsgeschichte der Tiere — Beohachtung 
iiud 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 
fmished according to the plan of Von Baer, but was issued by 
his publisher, after vainly waiting for the fmished manu- 
script. The final j^ortion, 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 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 intervals 
for several years. 

It is significant of the character of his Reflexionen that, 
although published before the announcement of the cell- 
theory, 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 born 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 

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, apj^eared 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 Sticda, Waldeyer, and others, we have 
a very entertaining autobiography of Von Baer, pu])lishrd in 1864, for pri- 
vate circulation, but afterward (1866) reprinted and placed on sale. 



of Sticda's Lijc oj Von Bacr (see Fig. 65). This, perhaps 
llu- 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 \'on Baer at about seventy years of age, 



reproduced in Fig. 66, is, however, destined to be the one by 
which he is commonly known to cmbryologists, since it forms 
the frontispiece of the great cooperative Handbook oj Eni- 

FiG. 66. — Von Baer at about Seventy Years of Age. 

bryology just published under the editorship of Oskar 
Von Baer's Especial Service. — Apart from special dis- 



covcries, \^on Bacr greatly enriched embryology 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 WoUi had distinctly foreshadowed the idea bv 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 \\'olff. He recognized the presence of three 
primiary layers — an outer, a middle, and an inner — out of 
v/hich the tissues of the body are formed. 

The Germ-Layers. — But it remained for Von Baer,* by 
extending his observations into all the principal groups of 
animals, to raise this conception to the rank of a general law 
of development. He was able to show that in all animals 

* It is of more than passing interest to remember that Pander and Von 
Bacr were associated as friends and fellow-students, under Dollinger at 
Wiirzburg. It was partly through the influence of Von Baer that Pander 
came to studv with Dollinger, 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 \'on Baer's work is dedicated " An 
meinen Jugendfreund, Dr. Christian Pander." 


except the very lowest there arise in tlie 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 \^on 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 nervous 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 class of amphibia. B, 
another figure of an ideal section, shows that, long before the 


day of microtomes, Von Bacr 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 
arc 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 

The generalization that embryos in development tend to 
recapitulate their ancestral history is frequently attributed to 
\on 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 Qgg 


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 



•'•^ . ^R 




— ^-^ 

















Fig. 67. — Sketches from Von Baer's Embryological Treatise (1828). 


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 

The Period from \^on Baer to Balfour 

In the period between \'on Baer and Balfour there were 
great general advances in the knowledge of organic structure 
that brought the whole process of development into a new 


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 e\'olution. 

The Cell-Theory. — The generalization that the tissues of 
all animals and ])lants 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 jjrotoplasm 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 place 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 w^as already opened, and it was fol- 
lowed, step by step, until the egg and the sperm came to be 


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, arc 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 w^ork of the body. In this w^ay arise the various 
tissues of the body, w^hich are, in reality, similar cells per- 
forming a simiilar 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 
W'ith protoplasm derived from tw^o parents. While questions 
regarding the origin of cells in the body were being answered, 
the foundation for the embryological study of heredity was 
also laid. 

Advances were now m^ore 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 

Apart from the general advances of this period, men- 
tioned in other connections, the work of a few individuals 
requires notice. 

Rathke and Remak were engaged with the broader as])ects 
of embryology, as well as with special investigations. From 
Rathke's researches came great advances in the knowledge of 


the development of insects and other invertebrates, and Remak 
is notable for similar work with the vertebrates. x\s already 
mentioned, he was the tirst 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. 

Koellikcr, i8i 7-1905, the veteran embryologist, for so 
manv vears a professor in the University of \\ urzburg, 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 Ylll, where also his services as a histologist 
are recorded. 

Huxley took a great step toward unifying the idea of germ- 
lavers throughout the animal kingdom, when he maintained, 
in 1 8-19, that the two cell-layers in animals like the hydra 
and oceanic hydrozoa correspond to the ectoderm and 
endoderm of higher animals. 

Kowalevsky (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 obser^•ations 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 



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 in\'olved in this 
conception that, in the present decade, it has been designated 
(Whitman) "the central fact of modern biology." The first 
clear expression of it is found in \'irchow's Cellular Pa- 
thology, published in 1S58. It was not, however, until the 








^^^^^^^^^^^^^E- ^'^^^^^vv^^^SuSilf 




Fig. 68. — A. Kowalevsky, 1840-1901. 

period of Balfour, and through the work of Fol, \^an Beneden 
(chromosomes, 1883), Bovcri, 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- 

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 

Darvv'in, in 1859, brought a new feature into its discussion 



by emphasizing the factor of natural selection. The general 
acceptance of the doctrine, \Yhich followed after fierce oppo- 
sition, had, of course, a ])rofound 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, rudimentary organs began to have 
meaning as hereditary sun'ivals, and the whole process of 
development assumed a different aspect. This doctrine 
supplied a new impulse to the interpretation of nature at 
large, and of the embryological 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 
nioving toward a better and m^orc consistent conception of 
the structure of animals and plants. A new comparative 
anatomy, more profound and richer in meaning than Cu- 
\ier'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 


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 were scattered 
through technical periodicals, transactions of learned societies, 



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 whole. 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 ])ublished, with ^Micliael 
Foster, The Elements oj Embryology. 

His University Career. — Balfour (Fig. 69) was born in 


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 INIichael 
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 
vears " voluntarv attendance on his classes advanced from 
ten to ninetv." He Avas 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 

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 cjuarto vol- 
umes, but the "Comparative Embryology" is Balfour's 
monument, and Avill 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- 



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 embryolo^ical 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, vith 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 observations 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 em^bryo. 
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 1821, 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 embryo of the whale- 
bone whale, but they are transitory and soon disappear with- 
out having been of service to the animal. In tlie embryos 
of all higher vertebrates, as is well known, gill-clefts and 
gill-arches with an apjjropriate circulation, make their ap- 


pcarancc, but disappear long before birth. These indica- 
tions, and similar ones, must have some meaning. 

Now whatever (jualities 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, may we not, by patching together our 
observations, be able to interpret the record, just as the his- 
lorv 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 WTitings of 
Fritz ]\Iuller. 

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. 



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 ix iSqo. 

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 


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, Whitmian, 
E. B. Wilson, and others. 

Although no attempt is made to review the researches of 
the recent 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 nervous system, the 
origin of nerve fibers, and his analysis of the development of 
the human embryo are all very 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- 
bryology. All previous w^ork 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 w^ork, as follows: "INIorphology 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 w^hich was a 
relatively simple stage ? The embryological history is traced 

Fig. 71. — WiLHELM His, 1831-1904. At Sixtv-four Years. 


out, and the palcTontological records are searched, until the 
evidence from both sources estabhshes 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 m^any others have 
contributed to the grovrth of this new division of embryology. 
Good reasons have been adduced for believing that c^ualitative 
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 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 observers, espe- 


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 
when the germ-layers are established. Some of the beautifully 
illustrated memoirs in this field are hidilv 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 homolosjv 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 embryology. 

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 embryological 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 ser^'ice to 


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. 




The recognition, in 1838, of the fact that all the various 
tissues of animals and plants are constructed on a similar plan 
was 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 elementary 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 Foreshadowings of the Cell-Theory. — In attempt- 
ingto 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 earl}' observers, ])ut ^^•ere not 




As long ago as 1665 Robert Hooke, ihc 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 
JMicrographia (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." 

Wc must not completely overlook the fact that Aristotle 
(384-322 B.C.) and Galen (130-200 a.d.), those profound 
thinkers on anatomical structure, had reached the theoretical 
position "that animals and plants, complex as they may 



appear, arc 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 witli 
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 Anatomv of 

Plants (1670). 

Lceuwenhoek, and Grew show so many pictures of the cel- 
lular construction of })lants 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 i)lants; 


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 shows 
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 observ^ations 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 
w^orked out the identity of structure of plants and animals 
as shown by their development. In his famous publication 
on the Theory of Development [Theoria Generationis) he used 
both plants and animals. 

Huxley epitomizes 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, 
which 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, 


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 ihustrious physi- 
ologist Haller his work remained unappreciated, and was 
finally forgotten, until it was revived again in 181 2. 

We can not show that \\'olff '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- 
philosophie,''^ we find, about i8c8, 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 


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 w-riters. 

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 somiC 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 mxCn 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. 



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 
served 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 

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.iih the simi- 
larity between the obser\ationsof Schleiden and certain of liis 
own upon animal tissues. Together they went to his labo- 


raloryand 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 w^hole 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 
where we used to work till nightfall by the side of our excellent 
chief, Johann jNIiiller. We took our dinner in the evening, 
after the English fashion, so that w^e 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 Wurzburg, where IM tiller, with rare 
discernment for recognizing genius, selected Schwann for 
especial favors and for close personal friendship. The influ- 
ence of his long association with ^liiller, the greatest of all 
trainers of anatomists and physiologists of the nineteenth 
century, must have been very uplifting. A few years later, 



Schwann found himself at the University of Berlin, where 
jMiiller 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- 



spcctcd in ihc uni\-crsity, 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- 


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 ^^ho gathers flowers, names 
them, dries them, and wraps them in paper, and all of whose 
wisdom consists in determining and classifying this hay 
w^hich 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 vrong, 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 ^^■as par- 
ticularly directed to the question, How does the cell originate ? 


and was published in Miillcr's Archiv, in 1838, under the 
German lillc of Ueber Phytogenesis. 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 obsers'ations exist at present upon the development 
of the cells of plants." 

He then soes on to define his view of the nucleus fcvto- 
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 observ^ations. On another point of 
prime importance Schleiden was WTong: 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 tw^o 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 vears. 

Schwann's Treatise. — In 1838, Schwann also announced 
his cell-theory in a concise form in a German scientific period- 


ical, and, later, to the Paris Academy of Sciences; but it was 
not till 1839 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 Untersuchtmgeniiber 
die U ebereinstimmung in der Structur iind dem Wachsthum 
der Thiere undPflanzen) 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, 
using it in its more extended signification, while, in a more 
limited sense, by the theory of cells we understand whatever 
miay be inferred from this proposition with respect to the 
powers from which these phenomena result." 


One comes from the reading of these two contributions 
to science with the feehng that it is really Schwann's cell- 
thcor}-, 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- 
theor}', 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 observers, 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 discovery, and for a long time his descrip- 
tion of sarcode remained separate; but in 1846 Hugo von 



^lohl, 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 w^as 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 vet 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, j\Iax 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 Schlciden 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- 


theory, in which the original generalization became consoli- 
dated with the protoplasm doctrine. 

Further Modifications of the Cell-Theory. — The reformed 
cell -theory was, howeyer, 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 ori<j;in of cells within the body of a multicellular 
organism, and of the relation between the primordial element 
and the fully developed tissues. Finally, ^^■hen observers 
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 necessary 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 wathin 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 ha ving, 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 



groups are set apart to perform particular duties. The divi- 
sion of physiological labor which arises at this time marks 
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 mod ill ed. 
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 proto})lasm 
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 aj^titudes. The 
nucleus, which is more readily seen than other cell dements, 


was sho^^n lo 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- 




' ■ ... .^V :.>^ 4g 

_.- -< _,- . 


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 



number — commonly from two to twenty-four — in (lilTcrcnt 
parts of animals and plants, they are, nevertheless, of the 
same number in all the cells of any particular plant or ani- 

^^ >»«<l 



(■v^-vi;s'^; K'-^'^r.l'^w ■•^ty;vt^ w^".-,— >\ <;.« 

•i^^' W>^ f'^-c^ \ {^W.-^'&JL^ 
.-____. / LizZ'^'y^ \ //oil? ^^ ^^^^ ysiv^y . 



V . 

i .4<<Sfcr^. 




\,_-vi^:. / 

Fig. 78. — Highly Magnified Tissue Cells from the vSkin of a 
Salamander in an Active State of Growth. Dividing cells with 
chromosomes are shown at a, 6, and c,. (After Wilson.) 

mal. As a conclusion to this kind of observation, it needs 
to be said that the chromosomes arc rerarded as the actual 
bearers of hereditary qualities. The chromosomes do not 



show in resting-stagcs 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 




^^^s^S^K r 







Fig. 79.— Diagram of the Chief Steps in Cell-division. 
(After Parker as altered from Fleming.) 

division exhibit the rod-like chromosomes, as shown at a, 
h^ and c. 

Centrosome. — The discovery (1876) of a minute spot of 
deeply staining protoplasm, usually just outside the nuclear 



membrane, is another illustration of the complex structure 
of the cell. x-\lthough the centrosome, as this S])Ot is called, 
has been heralded as a^ dynamic agent, there is not comi)lete 
agreement as to its purpose, but its presence makes it neccss- 
sary to include it in the defmition 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 some- 
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 
directlv, but the chromosomes concjre- 
gate around the equator of a spindle 
{D) formed from the achromatin; they 
then undergo division lengthwise, and 
migrate to the poles (£, F, G), after 
which a partition wall 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 hereditarv 
substance derived from both mater- 
nal and paternal huclei. This is brieily the basis for re- 
garding inheritance as a phenomenon of cell-life. 

A diagram of the cell as now understood (Pig. So) will 
be helpful in showing how much the conception of the cell 
has changed since the time of Schleiden and Schwann. 


Fig. 80. — Diaijrain 
of a Cell. (Moditied 
after Wilson.) 


Definition. — The definition of Vcrworn, made in 1895, 
ma\- be combined with this diagram: A cell is "a body con- 
sisting essentially of protoplasm 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) 
])igment granules, (4) oil globules, and (5) chlorophyll gran- 
ules." No definition can include all variations, but the one 
(|Uoted 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 series 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-w^all 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- 
lotrical science. 



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 discoveiy. 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 

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 ])rotoplasm, 
one has a wide range of choice in selecting the plant or the 
animal upon which to make obsers'ations. 

We may, for illustration, take one of the simj^lest of animal 
organisms, the amoeba, and place it under the high powers 



of the microscope. This little animal consists almost entirely 
of a lump of living jelly. Within the living substance of 
\\hich 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 developm.ent, 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 ama-ba is receptive and assimilative, that it is 
respirator}^ taking in oxygen and giving off carbonic dioxide, 
and that it is also secretory. 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 amoeba 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. 



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 

Fig. 81. — (,4) 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. Si B). 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 


(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 organismis 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 murmur of these tiny maelstroms as they 
whirl in the innumerable mvriads of livinsj 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. Both 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 



is usually credited with being the discoverer of protoplasm. 
His researches, moreover, Avere 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 vratchmakers, 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 geology and botany, and com- 
menced publication in those departments of science. 

About 1834 he began to devote his chief eft'orts 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 cVun Natural iste, 


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- 


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 rhizo})ods 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. 

Xo 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 



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, 1801-1S60. 

writer through the courtesy of Professor Joubin, and a copy 
of it is represented in Fig. S2. His picture bespeaks his per- 
sonality. The quiet refinement and sincerity of his face arc 


evident. Professor Joubin published, in 1901 {Archives dc 
Parasi/ologie), 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 miicroscopic 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 w^as 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 broudit verv definitelv 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 



were due to Dujardin, and, therefore, we must include him 
among the founders of modern biology. 

Purkinje. — The observations of the Bohemian investi- 
gator Purkinje (i 787-1869) form a link in the cliain of events 
leading up to the recognition of protoplasm. Athough 
Purkinje is especially remembered for other scientific contri- 


J9i f ;t ■ * 

Fig. St,. — Purkinje, 1787-1869. 

butions, he was the first to make use of the name protoplasm 
for living matter, by a})plying it to the formative substance 
within the eggs of animals and within the cells of the enibrvo. 
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 successi\c]y a pro- 



fcssor in ihc universities of Breslau and Prague. His ana- 
tomical laboratory at Breslau is notable as being one of the 
earliest (iS2^) 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 ]\Iohl (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, 1817-1891. 

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 water}^ 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 botanist Nagcli 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 Nageli (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 \^on 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 lirst employed the word 


protoplasm, stands somewhat aside, but his name, neverthe- 
less, should be connected with the establishment of the 
protoplasm doctrine. 

Von ^lohl (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 scientilic 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 wxTe one and the same substance. This notion was in 
the minds of more than one worker, but it is perhaps to Fer- 
dinand Cohn (1 828-1 89S) 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 j)lants fprotococcus), he said that vegetable proto- 
plasm and animial sarcode, "if not identical, must be, at 
any rate, in the highest degree analogous substances " 

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- 



ing period of the acceptance of the conclusion in its full 

De Bary. — ^^'c find, then, in the middle years of the 
nineteenth century the idea launched that sarcodc and pro- 
toplasm are identical, but it was not yet definitely established 

Fig. 86. — Ferdinand Cohn, 1828-1898. 

that the sarcodc 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 Bary 
(Fig. 87) on the myxomycetes, published in 1859. Here the 
resemblance between sarcode and protoplasm was brought out 



with great clearness. The myxomycetes are, in one condition, 
masses of vegetable protoplasm, the movements and other 
characteristics of which were shown to resemble strongly 
those of the protozoa. De Bary'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 1861, placed the conception of the identity 



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 confmed to the lower invertebrates, 
is also present in the tissues of higher animals, and there ex- 


hibits the same properties. The qualities 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 einc Zelle zii 
nenncn Jiahe), 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. SS) 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 

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 jilr Mikro- 
scopische Analomie. 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 modern 
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 


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 
livin<^ substance; now for the first time thev saw clearlv 
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 0] Species and Spencer's First Principles, 



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 miicroscope 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 stud ies 
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- 



tagioiis diseases. The three greatest nanies connected with 
the rise of bacteriology are those of Pasteur, Koch, and Lister, 
the resuhs 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 become 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 kboratory without contact 
or close association with living substance? This is a ques- 
tion of biogenesis — life from previous life — or of ahiogenesis 
— life without preexisting life or from inorganic matter alone. 

It is a question with a long history. 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 Pouchet'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 c^uestion of spontaneous origin of life was in 
a crude and grotesque condition. It was thought that frogs 


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 

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- 


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 jars, some of which were left uncovered, some 
covered with parchment, and others with fine wire gauze. The 
meat in all these vessels became spoiled, and Hies, being at- 
tracted by the smell of decaying meat, laid eggs in that which 
was exposed, and there came from it a large crop of maggots. 
The meat which was covered by parchment also decayed in 
a similar manner, without the appearance of maggots within 
it; and in those vessels covered by wire netting the flies laid 
their eggs upon the wire netting. There they hatched, and 
the maggots, instead of appearing in the meat, appeared on 
the surface of the wire gauze. From this Redi concluded 
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. 

Pie 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 w^ere due to the introduction of living germ.s 
from without. The good work begun by Redi was confirmed 
and extended by Swammerdam (1637-1681) and A'allisnieri 
(1661-1730), until the notion of the spontaneous origin of any 
forms of life visible to the unaided eve 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 
Academ.y of Crusca, Poetry as well as other literary com- 
positions shared his time with scientific occupations. His 



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 DegVInsetti, 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- 


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 ^^as 
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 Buff on, the great French nat- 
uralist, who had a theory of organic molecules that he wished 
to sustain. Needham (i 713-1784), 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 Xeedham's 
first experiments were published in 1 748. These experiments 


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 Needham believed 
that he had killed all living germs 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 
Pa via. 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 vcge- 



tables and meats which had been extracted by boiling, placed 
them in clear 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. go. — Lazzaro Spallanzai-ji, 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; 


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 caUed it, the 'vegetative force' of the infusion 
itself. Spallanzani easily disposed of this objection by sho^^•- 
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 difl"erent 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 worked, the more resistant atmospheric germs 
wxre 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 discover}^ of 
oxygen, one of the greatest scientific events of the eighteenth 
centur}^, was made by Priestley in 1774. It was soon shown 
that oxygen is necessary 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 


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 wifl 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 ivaicr 
"unll he jound quite as efjectiial as sulphuric acid.^^ 

Schwann's apparatus was similar in construction, except 


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 bv 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 Hclmholtz to show, 
as he did in 1843, that this 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 ^fuseum 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 Heter agenesis, "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. 


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, w^hich 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 oxvgen. Bv heating 
the retort, oxygen w^as 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 wdth oxygen imprisoned above the w^ater, 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, 
w^here 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 w^as 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- 


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 fohowers. 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 water by Pouchet. This, however, is probably not 
the only source of the organisms which were develofjed in 
Pouchet 's infusions. It is now known that a hay infusion 
is very dilhcult to sterilize by heat, and it is altogether likely 
that the infusions used by Pouchet were not completely 

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 

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 sufli- 


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 tlie 
spontaneous origin of life within them. 



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. 
Ill rough the bottom of this box he had fitted ordinary test 

Fig. 91. — Apparatus of Tyndall for Experimenting on Spontaneous 


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- 


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 was 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 differed 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 readv 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 difl'erent kinds 
of fluids from above, he was able to introduce these into 
dift'erent test tubes. These fluids consisted of mutton broth, 
of turnip-broth, and other decoctions of animal and vegeta- 


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 

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- 
organisms, 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 chemical changes inimical to life, 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 outside air. Within a few days' time the 
fluids which previously had remained uncontaminated were 
spoiling and teeming with living organisms. 

These experiments 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, 


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 appliances 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 contagiiim 
livum, 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 


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 
theorv that all contagious diseases are due to microscopic 

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 v/ay 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 vear 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-theory 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^i:fi»efation 
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. 


widefy circulated of the French journals — the Petit 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, bv 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. Fie 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 amehorating 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 Dole 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 


in the dedication of his book, Studies on Fermentation^ 
published in 1876: 

"To the memory of my Father, 

Formerly a soldier under the First Empire, and Knight of the Legion of 


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 


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 
dift'erently 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 up'on a crowd of 
connected problems of the highest public and scientific 
interest, ripe for solution, and requiring for their successful 


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 Ecole 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 chemiical 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 

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 : 'Mf 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 was the 
subject of fierce controversy; no investigations ever met 


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 (1865-1868) 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 ever}^ part of France. 
Even the inhabitants of obscure little towns and villages 
organized fetes, and clubbed together to send their small 


gifts " (Franckland). The total sum subscribed on the date 
of the opening ceremony amounted to 3,586,680 francs. 

The institute ^\•as formally opened on November 14th, 
1888, with impressive ceremonies presided over by the 
President of the Republic of France. The establishment 
of this institute v;as an event of great scientific importance. 
Here, within the first decade of its existence, were success- 
fullv 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 

Pasteur died in 1895, greatly honored by the whole v^orld. 
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, and 
is still living, engaged actively in work in the University of 
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 connected with a number of remarkable discoveries 
that are of continuous practical application in the science of 

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: 



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, Born 1843. 

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 t}'phoid fever, 
the last steps have not been completed, for the reason that the 



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 is Sir Joseph Lister (Fig. 94); born in 1827, he 
has been successively professor of surgery in the universities 

Fig. 94. — Sir Joseph Lister, Born 1827. 

of Glasgow fi86c) and of Edinburgh (1869), and in King's 
College, London (1877). His practical application of the 
germ-theory introduced aseptic methods into surgery and 
completely revolutionized that field. This was in 1867. In 
an address given that year before the British Medical Asso- 
ciation in Dublin, he said: "A\hen it had been shown by the 


researches of Pasteur that the septic property of the atmos- 
phere depended, not on oxygen 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 dressing some material capable of de- 
stroying the life of the floating particles." At hrst he used 
carbolic acid for this purpose. "The wards of which he had 
charge in the Glasgow Infirmary were especially affected by 
gangrene, but in a short time became the healthiest in the 
world ; while other wards separated by a passageway retained 
their infection." The method of Lister has been universally 
adopted, and at the same time has been greatly extended and 

The question of immunity, i.e.^ the reason why after 
having 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. 

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 
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 lo\\'er 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. 



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 

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 liereditary 
qualities are carried in the egg and the sperm — as it seems 
they must be — then it follows that these germinal elements, 
20 305 


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 cjuestion, 
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- 
oi)liers 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 within 
particular parts of the egg. It has come now to mean that 
development is a process of differentiation of certain qualities 
already laid down in the germinal elements. 

Darwin's Theory of Pangenesis. — In attempting to 


account for heredity, Darwin sa^^ clearly the necessity of 
]jroviding some mearis of getting all hereditar\- qualities com- 
bined within the egg and the sperm. Accordingly he orig- 
inated his pro\isional theory of pangenesis. Keeping in mind 
the fact that all organism.s begin their lives in tlie condition 
of single cells, the idea of inheritance through these micro- 
scopic particles becomes difficult to understand. liow is it 
possible to conceive of all the hereditary qualities being con- 
tained within the microscopic germ of the future being? 
Darv.'in 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 gerniinal 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 reJ)resentati^'es of the tissues of the 
parent form. 

Theory of Pangenesis Replaced by that of Germinal Con- 
tinuity. — This theory of Darwin ser\-ed as the basis for other 
theories founded upon the conception of the existence of |)an- 
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 \arious 


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 Hving thread 
that connects one generation with another. It thus appears 
that there enters into the 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 w^ork 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 


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 cellular Manifestly it was 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 undving^ value. 

When apphed to inheritance the idea of the continuity of 
living substance leads to making a distinction between germ- 
cells and bodv-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 continuil}-, through all 

A. & Wl. COLLEGE- 


time, of the germinal substance, is a conception of very great 
extent, and now underlies all discussion of heredity. 

In order to comprehend it, \Ye 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 

When the full significance of this conception comes to us, 
we see wh}- 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 

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 




investigators reached their conclusions independently, al- 
though there is great similarity between them. Although the 
credit for the first formulation of the law of germjnal con- 
tinuity docs 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 comer- stone of modern biology. 

The conclusion reached — that the hereditary substance is 
the germ-plasm — is merely preliminary ; the question remains, 
Is the germ-plasm homogeneous and endowed equally in all 
parts with a mixture of hereditary quahties? 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 protojDlasmic substance 
that carries the hereditary qualities? The earliest answer 
to this question was that the protoplasm, being the living 
substance, was the bearer of hereditv. But close analysis 
of the behavior of the nucleus during development led, 
about 1875, to the idea that the hereditary 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 pavi 
during cell-division, and it was very natural to reacli the 
conclusion that it is the |)articular bearer of hereditary 
substance. But, in 1883, \'an Beneden and Boveri made 
the discoverv that within the nucleus are certain dis- 


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 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 
reganled as the bearers of heredity, and their behavior during 
fertilization and development has been followed with great 

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 

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-Hce^ 
etc., in which a single polar globule is produced. 


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 
seo:mientation is verv 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 

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 

For some time the attention of investigators was concen- 
trated upon the nucleus and the chromosomes, but it is now 
necessar}^ 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 a])parently 
simple substance of the egg, areas which are deilnitely related 


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 Characteristics. — The belief 
in the inheritance of acquired characteristics was generallv 
accepted up to the middle of the nineteenth century, but the 
reaction against it started by Galton and others has assumicd 
great proportions. Discussions in this line 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 acquired characteristics. IMore 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 provoked by Weis- 
mann's theoretical considerations, have resulted in stimulat- 
ing experiment and research, and have, therefore, been 
beneficial to the advance of science. 

The Application of Statistical Methods and Experiments to 
the Ideas of Heredity. Mendel. — This feature of investigating 
questions of heredity is of growing importance. The first 
to complete experiments and to investigate heredity to any 
purpose was the Austrian monk Mendel (182 2-1 884) (Fig. 95), 
the abbot of a monastery at Briinn. In his garden he made 
many experiments upon the inheritance, particularly in peas, 
of color and of form; and through these experiments he 
demonstrated a law of inheritance wliich bids fair to be one 
of the great biological discoveries of the nineteenth century. 
He pubhshed his papers in 1866 and 1867, but since the minds 
of naturalists at that time were very much occupied with the 


questions of organic evolution, raised through the puljhcations 
of Darwin, the ideas of ^slendel attracted very httle attention. 
The principles that he established were re-discovered in 1900 
by De Vries and otlier botanists, and thus naturalists were led 
to look up the work of Mendel. 

Fig. 95. — Gregor Mendel, 1822-1884. 
Permission of Professor Bateson. 

The great discoverv of ^lendel mav be called that of 
the purity of the germ-cells. By cross- fertilization of })ure 
breeds of peas of different colors and shapes he obtained 
hybrids. The hybrid embodied the characteristics of the 
crossed peas; one of the characteristics appearing, and tlie 
other being held in abeyance — present wilhin the organization 



of the pea, but not visible. When peas of different color 
were cross-fertilized, one color would be stronger apparently 
than the other, and would stand out in the hybrids. This 
was called the dominant color. The other, which was held 
in abeyance, was called recessive; for, though unseen, it was 
still present within the young seeds. That the recessive 
color was not blotted out was clearly sho\\Ti by raising a 
crop from the hybrid, a condition under which they would 
produce seeds like those of the two original forms, and in 
equal number; and thereafter the descendants of these peas 
would breed true. This so-called purity of the germ-cells, 
then, may be expressed in this way: ''The hybrid, whatever 
its own character, produces ripe germ-cells, which produce 
only the pure character of one parent or of the other" 

Although Mendel's discovery was for a long time over- 
looked, happily the facts were re-discovered, and at the 
present time extensive experiments are being made with 
animals to test this law: experiments in the inheritance of 
poultry, the inheritance of fur in guinea-pigs, of erectness 
in the ears of rabbits, etc., etc. In this country the experi- 
ments of Castle, Davenport, and others with animals tend 
to support Mendel's conclusion and lift it to the position of 
a law. 

Rank of Mendel's Discovery. — The discovery by Mendel 
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 individuality in the offspring, has many possible 
practical applications both in horticulture and in the breeding 
of animals. The germ-cells of the hybrids have the dominant 
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-discovcrvof his 
law in 1900; but now he is accorded high rank. It ma\ be 
remarked in |)assing that the three leading names in the 
development of the theories of heredity arc those of Mendel, 
Galton, and Weismann. 

Galton. — The application of statistical methods is well 
illustrated in the theories of Francis Galton (Fig. 96). This 

Fig. 96. — Francis Galton, Born 1822. 

distiniifuished English statistician was bom in 1822, and is still 
hving. He is the grandson of Dr. Erasmus Darwin and tin- 
cousin of Charles. After })ublishing books on his travels in 
Africa, he beran the ex])erimental studv of hereditv 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 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 characteristics, in human 
families, and the inheritance of spots on the coat of certain 
hounds, and was led to formulate a law of ancestral inher- 
itance which received its clearest expression in his book, 
Natural Inheritance, pubHshed in 1889. 

He undertook to determine the proportion of heritage 
that is, on the average, contributed by each parent, grand- 
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 

Carl 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 Carl 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 notablv in this countrv, 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. 



It gradually dawned on the minds of men that the crust 
of the earth is like 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 li^ing 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 with fossil life. 

It has been determined by collecting and systematically 
studying the remains of this ancient hfe 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 



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 j^hilos- 
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 



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 1 718 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 earher 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 (i 638-1 686), 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 


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 like 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. x\n 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 
^losaic deluge. This was the prevailing \iew in the eight- 
eenth century. As observation 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. ^lilcs upon miles of superimposed 
rocks were discovered, all of them bearing quantities of 
animal forms, and the inter]:)rctation that these had been 
killed and distributed by a deluge became very strained. But 


to the reasoners who gave free play to their fancies the facts 
of observation afforded Httle difficuhy. Some declared that 
the- entire surface of the earth had been reduced to the con- 
dition of a pasty mass, and that the animals drowTied 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 early 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 theorv 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 Diluviance, 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 


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 tbe bones of human 

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 w^as founded on a comprehensive study of the bony 
system as wtII 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 li\ing 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 
livinsr animals the astoundini^; 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 


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 

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 life, 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 


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 Cu\ier 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 life 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 Hfe 
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, jMcturesque, 
highly honored, the favorite of princes, advanced to the 


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 l^y 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 th^t of WilHam 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, WilHam 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 rem.ains were distributed in strata, 
and that particular forms of fossil hfe 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 unvarying 
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. 


Summary. — The chief ste})SU]) to this lime in the i^rowlh 
of the science of fossil hfe may now be set forth in cate- 
gories, thout^h wc must remem1)er tliat the arlxances jjro- 
cecded concurrently and were nuich intermin<^led, so that, 
whatever arrangement we may ado})t, it does not represent 
a strict chronological order of events: 

I. The determination of the nature of fossils. (J wing to 
the labors of Da Vinci, Stcno,and Cuvier,the truth was estal)- 
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 catastroi)hism. The 
observations of Lamarck, that, while some species disap])ear, 
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 
ground 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 relati\e 
age of rocks may be determined bv an examination of their 
fossil contents. 

Upon the basis of the foregoing, we come to the next 

advance, viz.: 

\. The api)lication 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 


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 ])ublications 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 b}' the 
waters in cutting down the continents and in transferring the 
eroded material to other j^laces, 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 — bv all this he showed evidences of a series of 



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 Lvell, 1797-1S75. 

forms indicates a continual process of develo])ment of animal 
life; and that the disa})])earance of some forms, that is, their 
becoming extinct, was not owing to sudden changes, but to 
gradual changes. When this view was accei)ted, it overthrew 
the theory of catastrophism and replaced it b}- one designated 
uniformatism, based on the ])revalence of uniform natural 

This new concei)tion, with all of its logical inferences. 


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 life. 

We step forward now to the year 1859, to consider the 
effect upon the science of palaeontology of the publication of 
Darwin's Origin oj 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 oj 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 fife 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- 1 89 2) had his interest in fossil life 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- 
tihan characteristics. 

Agassiz. — Louis Agassiz (1807-1873) (Fig. 99) also came 
into close personal contact with Cuvier, and produced his 
first great work parth' under the stimulus of the latter. When 

Fig. 98. — Professor Owen and the Extinct Fossil Bird (Dinornis) 

of New Zealand. 
Permission of D. Appleton & Co. 



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 

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 


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. 

Huxley. — Thomas Henry Huxley (182 5-1 89 5) was led 
to study fossil life on an extended scale, and he shed light in 
this province as in others upon which he touched. With 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 

With the establishment of the doctrine of organic evolu- 
tion palaeontology entered upon its modern 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 



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. ioo. — 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. 



Leidy, Cope, and Marsh. — Among the early explorers of 
the fossils of the West must be named Joseph Leidy, E. D. 
Cope (Fig. loo), and O. C. j\Iarsh. These gentlemen all 
had access to rich material, and all of them made notable 
contributions to the science of pakeontology. 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 philoso])hical views. His extended ])ubii- 
cations under the direction of the United States Government 
have very greatly extended the knowledge of fossil vertebrate 
life in America. 


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, Handhiich der Palaeontologie (1876- 
1893), h^ 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- 

Zittel'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 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 studv 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 



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 ^luseum 

Fig. I02. — Karl von Zittel, 1839-1904. 

of Natural History, New York City. His profound and 
important investigations in the ancestry of animal hfe are 
now nearing the time of their publication in elaborated 


Palitontology, l)y 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 com])letely disappeared. ]\Iolds 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 
e])och, 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 pake- 
ontology deals witli 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 possiljle 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 


different collections a series containin.t; the XcandtTihal 
skull, the skulls of Spy and Kngis, and the Java skull de- 
scribed in 1894 by Dubois. There have also been found 
recently (November, 1906) in deposits near Lincoln, Xeb., 
some fossil human remains that occupy an intfrmcdiate 
position between the Neanderthal skull and the skulls of the 
lower representatives of living races of mankind. \\V 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 1S30. 
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 Osborn, the most important j)aheon- 
tological event of recent times was the discovery, in k^oo, of 
fossil beds of mammals in the Faytim lake-province of Kgyjjt, 
about forty-seven miles south of Cairo. Here are embedded 
fossil forms, some of which ha\e been already described in a 
volume by Charles W. Andrews, which Osborn says "marks 
a turning-point in the history of mammalia of the world.'' 
It is now established 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 studv of fossils from this district. 





The preceding pages have been de\oted mainl\- to an 
account of the shaping of ideas in reference to the architec- 
ture, die physiology, 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 w^iich the diverse forms of animals and jjlants 
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, howc\er, was rcserwd 
for the nineteenth century. The earlier naturah'sts acce])ted 
animated nature as thev found it, and for a lont^ 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 tlieir horizon 
deeper (juestions, 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 ]:)rocess of grachial exolution 
received general acceptance, as we liave said Ijcfore, onl\- 
in the last part of the nineteenth century, after the work of 
Charles Darwin; Ijut we shall presently see how the theory 
of organic development was thought out in completeness by 



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 supj^lying 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 


over the evolution- theory, and that it was bej^n'nnin.i^ to sur- 
render it. Such statements are misleach'n.L^ and tend to jht 
petuate the confusion regarding its j^rescnt status. P^urlher- 
more, the matter as set forth in writings h'ke the grotesque 
little book, At the Deathbed oj Darwinism tends to becloud 
rather than to clear the atmosphere. 

The theory of organic e\olution relates to the history of 
animal and plant life, while Darwin's theory of natural selec- 
tion is only one of the various attempts to j)oint 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 exjjlanation 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 lor 
the most part to the inl^uences 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 cons})icuous of those 
who are directing criticism against the general doctrine, 
maintaining that it is untenable. Working biologists will bi- 
the first to admit that it is not demonstrated by indubital)le 
evidence, but the weight of evidence is so com])elling 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. Sinn- 
Fleischmann speaks as an anatomist, his su])pression of 
anatomical facts with which he is accpiainted and his form of 
special pleading have impressed the biological world as lack- 
ing in sincerity. 


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 theorv and its various explanations. First we should 
aim to arrixe at a clear idea of what the doctrine of evolution 
i.->, and the basis upon which it rests; then of the factors w^hich 
have been emphasized in attempted explanations of it; and, 
finalh-, 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 b\- 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 emljryonic 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 searching out the early histor}- of mankind finds a 
parallel in the investigations into the question of organic 
evolution. In the buried cities of Palestine explorers have 


uncovered traces of ancient races and have in a measure 
reconstructed their history from fragments, such as coins, 
various oljjects of art and of household use, together with 
inscriptions on tombs 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 
stasres 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 a})plied 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 innumeraljle, and in a sin- 
gle order of the insect- workl, the beetles, more than 50,000 
species are known and described. In addition to living 


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, 
mav have through transformations merged into different 
kinds? This is not merely an idle question, insoluble from 
the verv nature of the case; for the present races of animals 
have a lineage reaching far into the past, and the question 
of fixitv 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 
thev 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 
thev have not been formed bv evolution; but if we find 
evidence of their transmutation into other species, then there 
has been evolution. 

It is well established 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 


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 arransjed 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 



begins. Thus their history for thousands of years bears 
testimony to the faet 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 


O " '» 

pond slu'll similar to the ])lanorbis, wliich is so common at 
the ])rcscnt lime. 

Fig. 104 shows some of these transformations, the finer 

Fig. 104. — Planorbis Shells from Stcinheim. (After Hyatt.) 

gradations being omittecL The shells from these two sources 
bear directly u};on the (juestion of wliellier or not species have 
held rit^idh' to their original form. 



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 
wa}' in which fossils have been produced w^e 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 w^e 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 wdth 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 wt come 
upon the successive ancestral forms, embracing several dis- 
tinct genera and exhibiting an interesting series of trans- 

If in this way we go into the past a half-million years, w^e 
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 wt 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. 


It is believed that in still older rocks a fne-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 Historv in New York Citv. Here, throusrh 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 Osborn, 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 ^larsh, is 

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- 



tor of the horse made by Charles R. Knight, the animal 
painter, under the direction of Professor Osborn. 

^^'hile the limbs were undergoing the changes indicated, 
other parts of the organism were also being transformed 

Fig. 105. — Bones of the Foreleg 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, 



of which the record is fairly well ])rescrved. ^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 fmd them, or were 
they evoh'ed by a process of transformation ? 


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 

The geological record, considered as a whole, shows that 
the earlier formed animals were representatives of the lower 
groups, and that when vertebrate anim^als 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 archaeop- 
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. x\nother 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 multiplied. 

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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vclop 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 Berhn Museum. (After Kayser.) 

and disappear. For illustration, in the young chick, devel- 
oping within the hen's egg, there appear, after three or four 



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 Shrirk (upper Hg,.) Compared with 
Those of the Embryonic Chick (to the left) and Rabbit. 

The heart and the l^lood- vessels at this stage are also of the 
fish-like type, but this condition does not last long; the gill- 
slits, or gill-clefts, fade away within a few days, and the 



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. 1 10. — The Jaws of an Embryonic Whale, Showing Rudimentary 


occurrence. They must have some meaning, and the best 
suggestion so far offered is that they are sur\ivals 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. 

ORGAXK^ i:V()LUTI()N 363 

Such traces arc like inscriptions on ancient columns — ihev 
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. 110). 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 stud\' 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 


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 oj 
Alan. 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 
born 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 rudimicntary ear muscles; of 
gill-clefts, etc. 

Antiquity of Man. — The geological history of man is 
imperfectly known, although sporadic explorations have 
already accumulated an interesting series, especially as 
regards the shape and capacity of skulls. The remains of 
early quarternary man have been unearthed in various parts 
of Europe, and the probable existence of man in the tertiary 
period is generally admitted. As Osborn says, "Virtually 
three links have been found in the chain of human ancestry." 
The most primitive pre-human species is represented by 
portions of the skull and of the leg bones found in Java by 
the Dutch surgeon Dubois in the year 1890. These remains 
were found in tertiary deposits, and were baptized under the 
name of PitJiecantJiropus erectus. The structural position of 
this fossil is between the chimpanzee, the highest of anthro- 
poid apes, and the "Neanderthal man." With characteristic 
scientific caution Osborn says that the Pithecanthropus 
"belongs in the line of none of the existing anthropoid apes, 
and falls very near, but not directly, in the line of human 


The second link is supplied by the famous Neanderthal 
skull found in the valley of the Neander, near Diasseldorf, 
in 1856. The discovery of this skull, with its receding fore- 
head and prominent ridges above the orbits of the eyes, and 
its small cranial capacity, created a sensation, for it was soon 
seen that it was intermediate between the skulls of the lowest 
human races and those of the anthropoid apes. Mrchow 
declared that if the skull was pre-human its structural char- 
acteristics were abnormal. This conclusion, however, was 
rendered untenable by the discovery in 1886 of similar skulls 
and the skeletons of two persons, in a cave near Spy in Bel- 

FiG. III. — 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.) 

gium. The " Spy man " and the " Neanderthal man " belong 
to the same type and are estimated to have been living in the 
middle of the palaeolithic age. 

The third link is in the early Neolithic man of Engis. 

And now to this interesting series of gradations has been 



added another by the discovery in 1906 of a supposed prim- 
itive race of men in Nebraska. The two skulls unearthed 
in Douglass County in that State indicate a cranial capacity 
falling below that of the " Australian negro, the lowest existing 
type of mankind known at present." 

Fig. Ill shows in outline profile reconstructions of the 
skulls of some of the fossil types as compared with the short- 
headed type of Europe. 

Pakeontological discoveries are thus coming to support 
the evidences of man's e\olution derived from embryology 
and archaeology. While we must admit that the geological 
evidences are at present fragmentary, there is, nevertheless, 
reasonable ground for the expectation that they will be 
extended by more systematic explorations of caverns and 
deposits of the quarternary and late tertiary periods. 

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 
svstem, and there exists such a finelv sjraded 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 o])inion 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 


e volution 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- 
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 lonsf 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 loring this 
about? This brings us naturally to discuss the theories of 



The impression so generally entertained that the doctrine 
of organic evolution is a \-ague hypothesis, requiring for its 
support great stretches of the imagination, gives way to an 
examination of the facts, and we come to recognize that it is 
a weh-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 arc not fixed, but undergo transforma- 
tions of considerable extent, there still remains to be accounted 
for the way in which these changes ha\'e 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 bv 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 



account for evolution, up to the announcement of the muta- 
tion-theory of De \>ies 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 undisco\'ered factors of e^'olution. Within a few 
years DeVries has brought into prominence the ideaof sudden 
transformations leading to new species, and has accounted 
for organic evolution on that basis. Further consideration of 
this theory, hov/ever, 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 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 thai 
doctrine in the modern sense. The earlier theories were 
more restricted in their reach than that of Lamarck. Eras- 
mus Darwin, his greatest predecessor in this held of thought, 
announced a comprehensive theory, which, while suggestive 
and forceful in originality, was diffuse, and is now only of 
historical importance. The more prominent writers on evo- 
lution in the period ])rior to Lamarck will ])e dealt with in 
the chapter on the Rise of Evolutionary Thought. 


Lamarck was born 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 o\crtaken by complete blindness, 
by the intellectual atmosphere that he created for himself, 
and by the superb confidence and affection of his devoted 
daughter Cornelie, who sustained him and made the truthful 
prediction tliat he would be recognized by posterity (" La 
posterite vans honorcra^''). 

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 \vas 
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 ])laced 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, 
lonii^er 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- 

Military Experience.— The Colonel would have liked to 
be rid of him, but owing to Lamarck's persistence, assigned 


him to a com])any; and, 1)eing 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 1)\- order of suc- 
cession was in command of tlie fourteen remaining gren- 
adiers. Ahhougli the French army retreated, Lamarck 
refused to mo\e with his scjuad until he recei\'ed directions 
from headcjuarters 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 b}' one 
of his comrades, unfitted him for military life, and he went to 
Paris and began the study of medicine, sup})orting 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 traininir 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 
liold this position long, but left it to travel with the sons 
of Buft'on as their instructor. I'his agreeable occu])ation 
extended o\er 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 beneatli his merits. 
Lamarck held this poorly ])aid position for several years, and 
was finall}' relie\ed by being appointed a i)rofessor in the 
newl\- established Jardin dcs Plantcs. 

He took an active part in the reorganization of the Royal 
Garden (Jardin du Roi) into the Jardin dcs PUinlcs. When, 


during the French Revolution, everything that was suggestive 
of rovaltv l)ecame o!)noxious 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 pro})Osed by Lamarck was adopted for the in- 

It was through the endorsements of Lamarck and Geoffroy 
Saint-Hilaire that Cuvier was brought into this great scientific 
institution; Cu\ier, who was later to be advanced above him 
in the Jardin and in public fa\-or, and who was to break 
friendship \\\{\\ 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, v/e know 
that it was painted before the publication of Lamarck's 
PJiilosopJiic Zoologiqiie, 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. — Lmtil 1794, 
when he was fiftv vcars of cH^q, Lamarck was de\'oted to 
botany, but on Ijeing 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, 



he succeeded. The fruit of his labors, the Natural His- 
tory of Invertebrated Animals (Hisiorie naturelle des Ani- 

FiG. 112. — Lamarck, 1774-1829. 

From Thornton's British Plants, 1805. 

maux sans Verlebres, 1815-1822), became a work of ij^reat 
importance. He took hold of this work, it sliould be re- 
membered, as an expert obser\er, trained to ri.i^id analysis 


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 foliage 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 eves. 

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. 


and an opinion to which he held unwaverin<^ly 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 evolutionarv ideas took form in his mind after he beoran 
the serious stud}' 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 invertei^rates. This avowal of 
belief in the extensive alteration of species was published in 
1801 as the preface to his Systeme des Animaux sans 
Vertebrcs. 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 \iews on evolution was published in 1802 
in his Recherches sur P Organise! I ion dcs Corpse 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 
180C, 1802, 1803, and 1806, since we find them full}- elal)- 
orated in his Philosophic Zoologiquc, published in 180Q, 
and this may be accepted as the standard source for the 
study of his theory. In this work he states two propositions 

^' * M. COLLEc 


under the name of laws, which ha\e been translated by 
Packard as follows - 

'' Firsl Law : In every animal which has not exceeded the 
term of its development, the more frequent and sustained 
use of anv 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 l)y the intiuence 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, 


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 ex])resses 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 hesoin 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 conce])tion, 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 cpiestion of the direct inheritance of variations 
acquired in the lifetime of an individual that his theory has 
been the most assailed. The belief 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 show-n 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 wc observe that the two 
factors discussed by Lamarck are Ijasal. AUhough it must 
be admitted that even to-dav we know little about eitlu-r 


\ariation or heredity, they remain basal factors in any theory 
of e\olution. 

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 i8oo*. 

*' It appears, as I have already said, that time and favorable 
conditions are the two ])rincipal 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 e^•ery day in order to cause her pro- 
ductions to vary, we can say that in a manner they are 

"The essential ones arising from the influence and from 
all the environinc^ media, from the diversitv 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 Ij}' 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 exolution of animal life, depending upon variations 
brougl;it about mainly through use and disuse of parts, 
and also by responses to external stimuli, and the direct 


inheritance of the same. His theory is comprehensi\e, 
so much so that he inckides mankind in his <^eneral con- 

Lamarck supposed that an animal having become 
adapted to its surroundings woukl remain relatively stable 
as to its structure. To the objection raised Ijy Cuvier that 
animals from Egypt had not changed since the da}'s when 
they were preser^'ed 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 indi\iduals 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 stabiHty, but "enjoy only a relative 

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 ]:)iogra])]iy of 
Lamarck appeared in igci, has made a thorough analysis 


of his, Avritings 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 especiall}' 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 Darw^in- Wallace 
principle of natural selection. The interesting connection 
betw^een the original conclusions of Darw^in and Wallace is 
set forth in Chapter XIX. 

Variation. — It will V)e noticed that t^^■o 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 \'ariation 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 entirelv sue- 

Fig. 113. — Charles Darwin, 1809-1882. 



cessfiil 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 
lirst 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 observations 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 ]j»lants 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 


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 inheritance. 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 j)ro\'isional theory of 
pangenesis, has been already considered fsee 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 dift"erent 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 ])rinci])le at work in 
nature, effects similar to those caused by artificial selec- 
tion will be produced. The selection b}- nature of tlie forms 
fittest to survive is what Darwin meant by natural selection. 
We can never understand the a])])lication. however, unless 
we take into account the fact that while animals tcnrl to 
multiply in geometrical progression, as a matter of fact the 


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 J 00 ,000 eggs. If the majority of these arrived at maturitv 
and gave rise to progeny, the next generation would represent 
a prodigious numl^er, and the numbers in the succeeding 
generations would increase so rapidly that soon there would 
not l)e 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 
sur^■i^■e, 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, a.nd 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 


strain and to survi\c. As another illustration, Darwin 
pointed out that natural selection had j^roduced a long-legged 
race of prairie wolves, while the timber wolves, which have 
less occasion for running, are short legged. 

We can also sec 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 been per- 
fected l)y evolution. Natural selection compels the eye to 
come u}) to a certain standard. Those hawks that are born 
with weak or defecti\-e \'ision 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 \ision or 
with vision that falls below the standard will Ije at a very 
great disadvantage. The shar]^-eyed forms will be ])reser\'ed 
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 ada])t 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 ex])lains 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 \iolent gales which sweep over those islands, while the 
weaker-winged forms would be left to ])er]xnuate their kind. 
Thus, generation after generation, the strong-winged beetles 
would be eliminated by a process, of natural selection, and 
there would be left a race of short -winged beetles derived 
from long-winged ancestors, hi this case the organs are 


reduced in their development, rather than increased; but 
manifestly the short -winged race of beetles is better adapted 
to live 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 progressi\'e series of steps whereby the organ- 
ism becomes better adapted to its surroundings. A similar 
instance is found in the supjjression 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 

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 serves 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 


Ijackground. They could be detected chietlv by their 
shadows when the sun was shinin<^. As he walked along 
the coast he came to a wide band of la\a whicli had llowed 
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 exce])t 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 howcon- 
S])icuous 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 woukl be destroyed, while the white 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 l^lack surface, 
they would be ])icked u]) by birds of ])rey and the black ones 
would be left. Tluis we see another instance of the operation 
of natural selection. 

Mimicry. - \\'e have, likewise, in nature a great number 
of cases that are designated mimicry. For illustration, cer- 
tain caterpillars assume a stiff ])ositi()n, resembling a twig 
from a branch. We ha\-e also leafdike butterllies. Tlie Ral- 
lima of Inrlia is a cons])icuous illustration of a butterlly 
having the u])])er 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 ha\e a mark across them 


rcseml)ling the mid-ril) of a leaf, so that the whole butterfly 
in the resting ]:)osition becomes inconspicuous, being pro- 
tected by mimicry. 

One can readily see how natural selection would l)e evoked 
in order to exi)lain this condition of affairs. Those forms 
that \aried 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 wimjs to 
a leaf would ser\e 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. 

^lany 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 

Sexual Selection. — There is an entirely different set of 
cases which at first sight would seem difficult to explain on 
the ])rinciple 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- 


tomcd to display their tail-feathers; the one with the most 
attractive display excites the pairing instinct in the hi<^hest 
degree, and becomes the selected suitor. In this wav, 
through the operation of a form of selection which Darwin 
designates sexual selection, possil^ly 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. 
]\Iuch has been said of late as to the inadequacy of natural 
selection. Herbert Spencer and Huxley, both accepting 
natural selection as one of the factors, doubted its complete 

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 oj 
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 tliat in the first edition of this 
work and subsequently I ])hiced in a most cons])icuous 
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 moditicalion.' This 
has been of no avail. Great is the power of steady mis- 


representation. But the history of science shows that for- 
tunately this power does not long endure." 

The reaction against the all-sufhciency 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 

Confusion between Lamarck's and Darwin's Theories. — 
Ik'sides the failure to understand what Darwin has written, 
there is great confusion, both in pictures and in writings, in 
reference to the theories of Darwdn 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 
illustration 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 savs: 


"A deer wiih a neck which was longer ])y half 
Than the rest of his famil}-'s — tr\' not lo laugh — 
Bv stretching and stretching became a giraffC; 
Which nobody can deny." 

The clever voung woman, Miss Kendall, however, in her 
Song oj the Ichthyosaurus, showed clearness in grasjjing 
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 ])rinci]jle which was enunciated 
bv Lamarck. This confusion between Lamarckism and Dar- 
winism is \er}' wide-spread. 

Darwin's book on the Origin oj Species, ])ublished in 
1859, was e])och-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 ])roportion of them would re])l}- that 
it is Darwin's Origin oj Species. Its influence was so great 
in the different domains of thought that we ma\' obserxe a 
natural cleavage between the thought iii reference to nature 
between 1859 and all preceding time. His other less widely- 
known books on Animals and Plants Under Domestication, 
the Descent oj Man, etc., etc., are also im])ortant contributions 
to the discussion of his theorx-. A brief account of Darwin, 
the man, will be found in Chapter XIX. 



Weismann's views have passed through various stages of 
remodeling 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 orisrinated his now famous theorv of hereditv, which 
has been retouched, from time to time, as the result 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- 



tions and those of my fellow-workers, not because T regard 
the picture as incomplete or incapable of imjjrovement, 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 
miore time and strength granted to me for its further elabora- 

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 theorv as a whole involves so manv 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 conline 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 English 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 conce])tion of 
the germ-plasm. As is well known, animals and })lants 
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 


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 
bodv-substance from sreneration 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 


the same stuff. The rise of the idea of .i^erminal continuity 
has been indicated in Cha])ter XI \', where it was pointed out 
that Weismann was not the originator of the idea, but he is nev- 
ertheless the one who lias 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 accjuired 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 w^hat the pro- 
toplasm shall be and how it will behave in development. 
Two masses of protojjlasm 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 

When the body is built anew from the germinal ele- 
ments, the derived cjualities come into play, and the whole 
process is a succession of responses to stimulation. This is 
in a sense, on the part of the protojjlasm, 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 bio|)hors, the elementary 
vital units, and their com])ination mto determinants, the 


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 maintained 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." 


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 

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 


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 

Inheritance of Acquired Characters. — Another funda- 
mental point in Weismann's theory is the denial that acquired 
characters arc 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? 

Alanifestlv, 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 


deprived of their tails, without yieldiag any evidence that 
the mutilations were inheritable. 

To take one other case that is less superlicial, it is gener- 
ally believed that the thirst for alcoholic licjuors has been 
transmitted to the children of drunkards, and while WY'ismann 
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. 

Xot\dthstanding 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 has been elaborating this theory (Fig. 114) is still living 
and actively at work in the University of Freiburg. August 
Weismann w^as born at Frankfort-on-the-Main in 1834. He 



was graduated at Gottingen in 1856, and for a short time 
thereafter engaged in the practice of medicine. This Une of 
activity (hd not, however, satisfy his nature, and he turned 
to the i)ursuit of microscopic investigations in embryology 

Fig. 114. — August Weismann, Born 1S34. 
Permission of Charles Scribner's Sons. 

and morphology, being encouraged in this work by Leuckart, 
whose name we ha\'e already met in this history. In 1863 
he settled in Freiburg as privat-docent, and has remained 
connected with the university ever since. From 1867 onward 


he has occu}nL'(l the chair of zoolog}' in tlial in.stilution. He 
has made his deparlment famous, especially by his lectures 
on the theory of descent. 

He is 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 has been afiiicted with an eye- 
trouble, but the inference sometimes made by those unac- 
quainted with his work as an investigator, that he has been 
obliged to forego practical work in the field in which he has 
speculated, is wrong. At intervals his eyes ha\'e strengthened 
so that he has been 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 

He is an accom})lished musician, and during the period 
of his enforced inactivity in scientific work he found much 
solace in ])laying "a good deal of music." "His continuous 
eye trouble must ha\e been a terrible obstacle, but may ha\'e 
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 ^Nlarie Gruber, who became the mother of my 
children and was my true com])anion for twenty \ears, until 
her death. Of her now J 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 


at this lime, for she read aloud excellenllv, and she not onlv 
look an inleresl in ni}- iheorelical and experinienlal work, 
])ut she also gave ])ractical assistance in it." 

In icSg3 he ]jublished The Gcrui-Plasui, A Theory of 
Heredity, a treatise which elicited much discussion. From 
I hat lime 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 the growth of |)lants, especiaily 
the evening primrose, and has shown that different species 
appear to rise suddenly. The sudden variations that breed 
true, and thus give rise to new forms, he calls mutations, and 
this indicates the source of the name applied to his theory. 

1y\\\\s Die Miitationstheorie, published in igoi, 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 \ariations, and 
Doints 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 
productioQ of new species" and that "as natural selection 
acts solely b\- accumulating slight, successive, favorable 
\ariations, 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 \>ies 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, 


and that it has given a i^rcat stimulus to expcrimcnlal slucHes. 
Experiment was Hkewise a dominant feature in Darwin's 
work, Init that seems to lia\e ])een almost overlooked in 
the discussions aroused by his conclusions; I)e Wies, by 
building upon experimental evidence, has led naturalists to 




• ^nf 



f " 


•i / 

t'' ' ^^^l^to 







1 ' 

Fig. 115. — Hugo de Vries. 

realize tliat the metliod of evolution is not a subject for 
argumentatixe discussion, Ijut for experimental in\estigation. 
This is most commendable. 

Dc Vries's theory tends also lo widen llie field of explo- 
ration. J>)a\enport, Tower, and others ha\e made it clear 
that sj^ecies ma\- arise by slow accumulations of trixial \aria- 
tions, and that, while the formation of S})ccies 1)\ mutation 


may be admitted, there is still abundant evidence of evolu- 
tion without mutation. 

Reconciliation of Different Theories. — All this is leading 
to a clearer ai)preciation 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. ^luta- 
tion is not a substitute for natural selection, but a cooperating 
factor; and neither mutation nor natural selection is a sub- 
stitute for the doctrine of the continuity of the germ-plasm. 
Thus we may look forward to a reconciliation between 
apparently conflicting views, when naturalists by sifting 
shall have determined the truth embodied in the various 
theories. One conviction that is looming into prominence is 
that this will be promoted by less argument and more ex- 
perimental 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 S pedes ^ 

Summary. — The number of points involved in the four 
theories considered above is likely to be rather confusing, 
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 tlie principle of use and 


2. Heredity: The variations are inherited directly and 

improved in succeeding generations. 
A long time and favorable conditions are required 
for the })roduction of new species. 

II. DarAvin's Theory of Natural Selection. 

1. \'ariations assumed. 

2. Heredity: Those slight variations which are of use 

to the organism will be perpetuated by inher- 

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 adxantage 
to the organism, and their gradual improvement, 
leads to the production of new species. 

III. 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 princi])le that the 

offspring is composed of some of the same stuff 
as its parents. The body-cells are not inherited, 

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 (jualities of the germ-plasm. 
The purpose of amphimixis is to gi\'e rise to vari- 
ations. The direct intluence of environment has 
produced variations in unicellular organisms. 


5. Weismann adopts and extends the principle of 
natural selection. Germinal selection is exhibited 
in the germ-plasm. 
IV. De X'ries'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. 

Among the other theories of evolution that of Eimer is 
the most notable. He maintains that variations in organisms 
take place not fortuitously or accidentally, but follow a per- 
fectly determinate direction. This definitely directed evolu- 
tion is called orthogenesis. He insists that there is con- 
tinuous inheritance of acquired characters, and he is radically 
opposed to the belief that natural selection plays an important 
part in evolution. The title of his pamphlet published in 
1898, On Orthogenesis and the Impotence oj Natural Selection 
in S pccies-For motion, gives an indication of his position in 
reference to natural selection. A consideration of Elmer's 
argument would be beyond the purpose of this book. 

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 svnonvmous terms. 
The distinction between the general theory and any particular 
explanation of it has, I trust, been made sufficiently clear in 
the preceding pages. 



A CURRENT of evolutionary thought can be traced through 
the literature dealing 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 • 
mav 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 slate 
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 
. Linnieus by defining a S])ecies had fixed the attention of 



naturalists upon the distinguishing features of the particular 
kinds of animals and ]:)lants. 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 \icw 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 

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 


first of the great theologians to discuss specifically the c^ues- 
tion of creation. His ])osition is an enlightened one. He 
says: "It \ery often haj^jjens 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.) 

x\ugustine's view of the method of creation was that of 
derivative creation or creation causalitcr. His was a natural- 
istic interpretation of the Alosaic 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 b)- many 
theologians of the nineteenth century. 

The next theologian to take up the question of creation 
was St. Thomas Acjuinas (12 25-1 274) in tlie thirteenth cen- 
tury. He (juotes St. Augustine's view with approval, but 
does not contribute anything of his own. One should net 
hastily conclude, however, because these views were held by 
leaders of theological thought, that they were unixersally 


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 which was 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 ope re 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 interestinsf 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 theoloL^v; what is not so i^enerallv realized is that the 
Aristotelian notion of the development of life led to the true 
interpretation of the ^losaic account of the creation. 

"There was in fact a long Greek ])eriod in the history 
of the e\olutionary idea extending among the Fathers of the 
Church and later among some of the schoolmen, in their 


commentaries ii])on creation, wliich accord \ery closel)' with 
the modern theistic conce])tion of evolution. If the ortho- 
doxy of Augustine liad remained the teaching of the Church, 
the final establislimcnt of evolution would ha\e 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 u])on 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 s])eciric form 
the o])inion of the English-speaking clergy and of the 
masses who read his book. When the doctrine of ori^anic 
evolution was announced, it came into conllict 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 
Buffon, 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 173c; to the time of his death 
he was the superintendent of the Jardin du Roi. He was a 
man of elegance, with an assured ])Osition in society. He 
was a delightful writer, a circumstance that enabled him to 
make natural history ])opular. It is said tliat the advance 
sheets of Buffon's Histoirc NaliircUc were to be found on the 
tables of the boudoirs of ladies of fashion. \\\ that work he 
suggested the idea that the different forms of life were grad- 
ually i^roduced, but his timidity and his prudence led him 
to be obscure in what lie said. 



Packard, who has studied his writings with care, says 
that he was an evolutionist throui^h all periods of his life, not, 
as is commonly maintained, belie\ing first in the fixity of 
species, later in their changeability, and lastly returning to 
his earlier 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 



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 fortv-four \oI- 
umes of his works, would now be regarded as in a degree 
superficial and valueless. But they appeared thirtv-four 
years before Lamarck's theory, and though not e])Och-making, 

Fig. 117. — Erasmus Darwin, i 731-1802. 

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 published the Zoonomia. Li this 
work he stated ten ])rinciplcs; among them lie vaguely 
suggested the transmission of acquired characteristics, the 
law of sexual selection — or the law of battle, as he called it — 


protective coloration, etc. His work received some notice 
from scholars. Paley's Natural Theology, for illustration, 
was written aiirainst it, althouii^h Palev is careful not to men- 
tion Darwin or his work. The success of Paley's book is 
])robably one of the cliief causes for the neglect into which 
the views of Buff on and Erasmus Darwin fell. 

Inasmuch as Darwin's conclusions were ])ublished before 
Lamarck's book, it would be interesting to determine whether 
or not Lamarck was inlluenced by him. The careful con- 
sideration of this matter leads to the conclusion that Lamarck 
drew his ins])iration 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 parallelism 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 oj 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 ha\'e 
been evolved from the modification of a few parental types. 
Accordingly he should be accorded a place in the history of 
evolutionarv thought. 

Opposition to Lamarck's Views. — Lamarck's doctrine, 
which was published in definite form in 1809, has been 
already outlined. We may well in(iuire. 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 


reco^T^nizc 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 readil}- understood 
as there was in Darwin's book on the doctrine of natural 

The tem]:)orary disappearance of the doctrine of or<^anic 
evolution which occurred after Lamarck exjjounded his theory 
was also owing to the reaction against the speculations of 
the school of N atur-Philosophic. The extravagant specula- 
tion of Oken and tlie other representatives of this school 
completely disgusted men \\\\o were engaged in research by 
observation and ex])eriment. The reaction against that 
school was so strong that it was difhcult to get a hearing for 
any theoretical speculation; l)ut Cu\-ier's inlkience 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 catastro])hism 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 ]jre-delineation, so that it must be admitted 
that whenever he forsook observation for s])eculation he 
was singularly unhappy, and it is undeniable that his ])osi- 
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 (\ivier and SaintTIilaire. 
The latter (Fig. 118) was in early life closely associated with 
Lamarck, and shared his \iews in reference to tlie ()rigin of 
animals and ]^lants; though in certain ])oints Saint-Hilaire 
was more a follower of Huffon than of Lamarck. Strangely 
enough, Saint-Hilaire was regarded as the stronger man of 



the two. He was more in the public eye, but was not a man 
of such deep intellect uaHty as Lamarck. His scientific repu- 
tation rests mainly u])on his Philosophie Auatonnque. 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 in\'olved 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 


case. He pointed triumphantly to the four branches of the 
animal kingdom which he had established, maintaining that 
these four branches represented four distinct tyj^es of organi- 
zation; and, furthermore, that fixity of species and fixitv of 
type were necessary for the existence of a scientihc natural 
history. Wc 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, w^re 
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, 18^0. 
The wide and liyely 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 : 

"^londay, Aug. 2d, 1830. — ^The new^s of the outbreak of 
the reyolution 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, Svhat 
do vou think of this s^reat 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 dis])ute between 
Cu\ier and Geoffroy de Saint-Hilaire, whicli has broken out 
in the Academy, and which is of such great im}jortance to 
science.' This remark of Goetlie came upon me so unex- 
pectedly that I did not know what to say, and my though is 
for some minutes seemed to have come to a complete stand- 
still. 'The affair is of the utmost importance,' he con- 


evolution, was unable to state explicitly what these causes 

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 fohowing 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. 


though ^Ir. 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 Linn^ean Society. 

"Taken in the order of their dates, they consist of: 

" I. Extracts from a MS. work on species, by JNIr. 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 oj 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 oj Organic Beings in 
a State oj Nature ; on the Natural Means oj Selection; on the 
Comparison oj 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 view^s, and which shows that these 
remained unaltered from 1839 to 1857. 

''3. An essay by Mr. Wallace, entitled On the Tendency 
oj Varieties to Depart Indefinitely jrom 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 Air. 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 published 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 Air. \\'allace), the memoir which 
he had himself written on the same subject, and which, as 


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 JNIr. 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 
Linncean 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 public. 

"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 
shown in P'ig. 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 Lije and Letters oj 
Charles Darwin (1887) and in More Letters oj Darwin {1 go ;^), 



both of which are iUustratccl by ])ortraits 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 naturaUst and of his 
personal characteristics. 

He is described as being about six feet high, but Avith a 
stoop of the shoulders which diminished his aj^parent height; 

Fig. 119. — Charles Darwix, 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 


about his manner, a constant deference to others, and a 
facuky for seeing the best side of everything and every- 

He was most affectionate and considerate at home. The 
picture of Darwin's Ufe 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 plaving 
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 life, 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 


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 left there after two sessions, 
at the suggestion of his father, to study for the Church, He 
then went to the Uni\Trsity of Cambridge, where he remained 
three years, listening to "incredibly dull lectures." After 
taking his baccalaureate degree, came the event vhich 
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. In 
Cambridge he had manifested an interest in scientific study, 
and had been encouraged by Professor Henslow, to whom 
he was also indebted for the recommiendation to the post on 
the 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 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 fixing forms in 
field and forest. He observed the correspondence in type 


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 obser\'ations 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 Downs. — On his return to England, after spending 
some time in London, he purchased a country-place at Downs, 
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 eve- 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; ^^d from 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 


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- 

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 noteworth}- circumstance that the idea of natural 
selection came to both by the reading of the same book, Mal- 
thus 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 jormation 
oj 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 som'e 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 suft'ering 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 88° Fahr., the problem again presented 
itself to me, and something led me to think of the 'positive 



checks' described by Alalthus 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, 120. — Alfred Russel Wallace, born 1823. 

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 bv these checks must be on the 


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 of 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 of Man, etc., etc., expanded his theory, but none of 
them effected so much stir in the intellectual world as the 
Origin of Species. 

This skeleton outline should be filled out by reading 
Darwin'' s Life and Letters, by his son, and the complete 
papers of Darwin and Wallace, as originally published in 
the Journal of the Linncean Society. The original papers 
are reproduced in the Popular Science Monthly for Novem- 
ber, 1901. 

Wallace was born in 1823, and is still living. He shares 
with Darwin the credit of propounding the theory of natural 
selection, and he is notable also for the publication of import- 
ant books, as the Malay Archipelago, TJie Geographical Distri- 
bution 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. 
In England such a man was found in Thomas Henry Huxley 
(1825-1895). He was one of the greatest popular exponents 



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 anvthins^ 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 way 
by urging the pursuit of scientific studies by high-school 
and university students, and by bringing science closer to 


the people. He was a pioneer in the laboralor\- teacliin<^ of 
biology, and his Manual has been, e\'er since its publica- 
tion in 1874, the inspiration and the model for writers of 
directions for practical work in that Jleld. 

It is not so generally known that he was also a great 
investigator, })roducing a large amount of purely technical 
researches. After his death a memorial edition of liis scien- 
tific memoirs was published in four large (juarto volumes. 
The extent of his scientific output when thus assembled was 
a surprise to many of his co-workers in the held of science. 
His other writings of a more general character have been 
collected in fourteen quarto volumes. Some of the essavs 
in this collection are models of clear and vi<=!;orous English 
stvle. Mr. Huxlev 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 Aliiller 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 Lije 
and Letters of TJiomas Henry Huxley, by his son. 

Haeckel. — Ernst Haeckel, of Jena, born in 1834 (Fig. 122), 
was one of the earliest in Germany to take up the de- 
fense of Darwin's hypothesis. As early as t866 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 popularlv believed to represent the best scientific 
thought on the matter, those written for the general ])ublic 
are not regarded by most biologists as strictly representative. 



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 amonsr 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. x\fter 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 


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- 




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 



to establish the same basis for thinkini^ about the ori^anizalion 
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 tlie days of \'esalius 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 ])revalence of uni\ersal 
laws in the production of all ])henomena. In its ])rogress 
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 b}- 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 develo])ment. 

The Notable Books of Biology and their Authors. — The 
progress of biology has been owing to the efforts of men of 
\'ery 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 ha\e formed the starting-j^oint 
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 Fabriai 11543), and Harvey, 
Dc Motu Cordis ct Sanguinis (1628), laid the founckuions of 
scientific method in biology. 

The pioneer researches of Malj^ighi on the minute anat- 
omy of t)lants and animals, and on the development of tlie 


chick, best represent the progress of investigation between 
Harvey and Linnaeus. The three contributions referred to 
are those on the Anatomy oj Plants {Anatome Plantanim, 
1675-1679); on the Anatomy oj the Silkworm {De Bombyce, 
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 Natura (twelve editions, 
1 73 5-1 768) of Linnaeus, a work* that had such wide in- 
fluence in stimulating activity in systematic botany and 

Wolff's Theoria Generationis, 1759, and his De Formatione 
Intestinorum, 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 Regne Animal, 1816, applied the principles 
of comparative anatomy to the entire animal kingdom. 

The publication in 1800 of Bichat's Traite des Membranes 
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 Entwicklungsgeschichte der Thiere), 1828, is an almost 
ideal combination of observation and conclusion in embry- 

The Microscopische Untersuchungen, 1839, of Schwann 
marks the foundation of the cell-theory. 

The Handbook of Johannes ]Muller (Handbiich 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. 


Darwin's Origin oj Species, 1S59, is, from (xir {jrcscnt 
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. 

li 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 oj 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, \'esalius, 
Harvey, Malpighi, Linnaeus, Wolff, Cuvier, Bichat, Lamarck, 
Von Baer, J. IMiiller, Schwann, Schultze, Darwin, Pasteur, 
and Cope. 

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 Koclliker, who is not mentioned, but the 
former must stand in the list on account of his connection 
with the ccll-theorv. Mrchow, 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 somic of the more e\ident intlucnces 
that dominate biological investigation at tlie present time, 


nothing more than an eaumcration 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. INIuch 
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 tlie 
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 

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 th^'nness and regular- 

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- 


tire histological elements so that they may be viewed as solids 
has come to supplement the study of sections. Reconstruc- 
tion, by carving v^ax 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 metliod 
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 ne\'er- 
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 alreadv 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 o\er 
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 inlhiences tend- 
ing to advance biology, none is more important than the aj)- 
plication of experiments to biological studies. Tlie exj^er- 
imental method is in reality 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 


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, where 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 — cxperimients that test the laws of 
ancestral inheritance and throw great light upon the ques- 
tions introduced by the investigations of Mendel and De 
\>ies. The investigations of De Vries on the evolution of 
plant-life occupy a notable position among the experimental 

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 


changing the chemical environment, etc. There is some 
internal mechanism in living matter that is inlluenced 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). 
Alarine animals arc 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 larva? 
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 wav in which animals will react toward liiifht 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 investigators to look 
beneath the surface and to make im])ortant deductions 
regarding the nature of psychological processes. 

A line closely allied to experimentation ih the application 
of statistics to biological j^rocesses, such as those of growth, 


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 ^•iew 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 in\-estigations 
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. 


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 wonderfuHy comphcated 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 ner\'ous 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 ])y 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 


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 apphcation to practical forestry, 
and in sanitary sciences. This kind of research is also ap- 
plied to the study of food-supply for fishes, as in 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. 

Lender this geaeral head should be mentioned stations 
under the control of the Carnegie Institution, the various 
scientific surveys under the Government, and the L^nited States 
Fish Commission, which carries on investigations in the bi- 
ology of fishes as well as observations that affect their use 


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 
maintenance 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 jilr Mikroscopische Anatomic, 
founded in 1864 by Schultze and continued to the present 
tim.e. 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 Morphologisclies 
Jahrhuch of Gegenbaur, and Y^odYi^ev^ s Zeitschrijt jiirWissen- 
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, 
edited by CO. Whitman, passed through seventeen volumes 
and was maintained on the highest plane of scholarship. 
The fine execution of the plates and the high grade of typo- 
graphical work made this journal conspicuous. It repre- 


sents in every way an enterprise of which Americans can be 
justly proud. The American Journal of Anatomy is now 
fining the field left unoccupied by the cessation of the Journal 
of Morphology."^ In the department of experimental work 
many journals have sprung up, as Bionietrica, edited by Carl 
Pearson, Roux's Archiv jilr Enlwickhmgs-Mcchanik, 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 Historv, in New York Citv, 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 Faytam 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 interesting 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 equi])ped laboratories, in the 

* It is a source of gratification to biologists that — thanks to the Wistar 
Institute of Anatomy — the publication of the Journal of Morphology is to 
be continued. 


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. Wliile 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 ? 


The books and articles relating to the history of biology arc 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 list. 


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 

Sachs. History of Botany, 1890. Excellent. Articles in the Botauicul 
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: \'esalius 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 uf 

Foster. Lectures on the History of Physiology, 1901. Fascinatingly 
written. Notable for poise and correct estimates, based on the u-^e of 
the original documents. 

Geddes. a Synthetic Outline of the History of Biology. Proc. Roy. Soc. 
Edinb., 1885-1886. Good. 

2Q 449 


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. Smitlison. Inst., 1900. 
Buckle. History of Civilization, vol. I, second edition, 1870. 
Macgilivray. Lives of Eminent Zoologists from Aristotle to Linnaeus. 
Merz. a History of European 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 are: 

Biology by Huxley; Protoplasm by Geddes; History of Anatomy 

by Turner. 
Chambers's ENCYCLOPiEDiA. 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. 
P.'^RKER and H.-^swell. 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. 
PuscHM.\NN. 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 m the interests 

of the history of zoology. 



TEN, founded 190 1. 

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, 
zodlogies, etc. 

Evolution. The bibliography of Evolution is given below under the 
chapters dealing with the evolution theory. 



Ancient biological Science: Cams; 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: ^Slagilivray; 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). 


\'esalius: Roth, Andreas VesaHus 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.; Pettigrcw; 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. G.a.len: Pettigrew; Huxley in 
his essay on William Harvey. 


H.\rvey: Foster, Lecture II, with cjuotations, excellent; Dalton, History 
of the Circulation; Huxley, William Harvey, a critical essay, Harvey's 
Works translated by Willis, with biography, Sydenham Society, 1S47; Life 


of Harvey by D'Arcy Power, 1S98; 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. Ver\' interesting. 


Hooke: Biography in encyclopaedias, his microscope in Carpenter, The 
Microscope and Its Revelations, Sth ed., 1900. 

Malpighi: Richardson, vol. II; Same article in The Asdepiad, vol. X, 
1893; Atti, Life and Work, in Italian, 1847, portrait; Pettigrew, vol. II; 
Marcello Malpighi e I'Opera Sua, 1897, a collection of addresses at the 
unveiling of Malpighi's monument at Crevalcuore, that by KoelUker 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. Littlebury edition, Lond., 1687, contains posthumous papers and 
biography; separate works not uncommon; Traite du \'er a Sole, Mont- 
pellier, 1878, contains his life and works. 

Swammerdam: Life by Boerhaave in Biblia Nature, 1735; 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 Asdepiad, vol. II, 1885, portrait, signature, and other 
illustrations; Arcana Naturae; Selected works in English, 1758; Locy, 
Pop. Sci. Mo., April, 1901. 


Lyonet: The Gentleman s Magazine, LIX, 1789; the famous Traite 
Anatomique, etc., 1750, 1752, not rare. Reaumur: Portrait and Hfe in 
Les Savants Modernes, p. 332. Roesel: Portrait and biography in Der 
monatlich herausgegebenen Inseden 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. 



ThePhysiologus: Carus, White (for titles sec General List). Gesxer: 
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. a7. Jonston: 
Macgilivray. Ray: Macgilivray; Nicholson; Memorial of, in the Ray 
Society, 1846; Correspondence of, Ray Soc, 1848. Linnaeus : Mac- 
gihvray; 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 Darwix: 
Geddes, Proc, Roy. Soc. Edinb., vol. 13, 1884-1886. 


Camper: Naturahst's Library, vol. VII; Vorlesungen, by his son, with 
short sketch of his Hfe, 1793; Cuvier, loc. cit.; Kleinere Schrijten, 2 vols, 
with copper plates illustrating brain and ear of fashes, etc., 1 782-1 785. 
John Hunter: The Scientific Works of, 2 vols., 1861; The Asclepiad, vol. 
VIII, 189 1 ; 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 ^yorks 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. 
Cu\iera C. M. Paff, 1 788-1 792, translated from the German, 1858. Cuvier s 
numerous writings — The Animal Kingdom, Lefons d'Anat. Comparec, etc. 
• — are readily accessible. H. Milne-Edwards : Biographical sketch in .4 nu. 
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. Xatur- 
alist, 1897; Obituary notice, with portraits, Am. Naturalist, 1897; Pop. 
Sci. Mo., vol. 19, 188 1. 


Bichat: Pettigrew; Buckle, Hist. Civ., vol. I, p. 630; The Hundred 
Greatest Men; Les Savants Modernes, p. 394; The Practitioner, vol. 56, 
1896. Koelliker: His Autobiography, Erinnerungen aus Meinem 


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, 1891, 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, 


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. 38 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; 
Briefe von J. Muller an Andres Retzius (1830-185 7), 1900; His famous 
Handbuch der Physiologic 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. 


Good general account of the Rise of Embryology in Koelliker'sEmbryolo- 
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 Embryologist, Brooks in /. Hop. 
Univ. Hospit. Bull., vol. \TII, 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 em.bryological 
treatises. Wolff: Wheeler, Wolff and the Theoria Generationis, in 
Woods HoU Biological Lectures, 1898; Kirchoff in Jenaische Zeitschr., 


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. \'ox 
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 Stolzle, 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. }. Mik. Ajiat., 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. 


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. Schleidex: 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, 1S74. 
Schwann: Life, Pop. Sci. Mo.,\o\. 37, 1900; Sa Vie at Scs Travaux, 
Fredericq, 1884; Nachruf, Henle, Archiv f. Mik. Anat., vol. 21, 1882; 
Lankester, Nature, vol. XXV, 1882; The Practitioner, vol. 49, 1S97; The 
Catholic World, vol. 71, 1900. Translation of his contribution of i83() 
(Mikroscopische Untersuchungen ueber die Uebereinstimmung in der Struc- 
tur und dem Wachstum der Thiere und Pflanzen), Sydenham Soc, 1847. 


On the Physical Basis of Life, Huxley, 1868; Rejirint in Method.^^ and 
ResuUs, 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. {Botaniquc), 


vol. 4, p. 367, 1835. Von Mohl: Sachs' History of Botany, i8go. Trans- 
lation of his researches, Sydenham Soc, 1847. Cohn: Blatter der Er- 
innerung, 1898, with portrait. Schultze: Necrology, by Schwalbe in 
Archiv f. Mik. Anat., vol. 10, 1874, \\-ith portrait. Schultze's paper found- 
ing the protoplasm doctrine in Archiv f. Anat. und Phys., 1861, entitled 
Ueber Muskelkorperchen und das was man eine Zelle zu nennen habe. 


Spontaneous Generation: Tyndall, Pop. Sci. Mo., vol. 12, 1878; 
Also in Floating Matter of the Air, 1881 ; J. C. Dalton in A^. Y. Med. Journ., 
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. Spallanzani: Foster, Lects. on Physiol.; 
Huxley, loc. cit.; Dunster, lo c. 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. I, 1893; Also McClure^s, vol. 19, 1902, review of \'allery- 
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. 
36, 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 Inoculation of 
Wright, Harper^s Mag., July, 1907. 


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; also in his Study of Animal Life, 1892. Mendel: Mendel's 
Principles of Heredity, with translations of his original papers on hybridi- 


zation, Bateson, 1902; Mendel's Versuchc iiber Pflanzcnhybridcn, two 
papers (1865 and i86g), edited by Tschermak, 1901; Ann. Rept. Smithson. 
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; 
Galton's Natural Inheritance, 1889. Weismann: Brief Autobiograjjhy, 
with portrait, in The Lamp, vol. 26, 1903; Solomonsen, Bcricht iiber die 
Feier des 70 Geburtstages von August Weismann, 1904; Weismann's The 
Germ -Plasm, 1893, and The Evolution Theory, 1904. 


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 VH. 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., 
vol. 13, 1878; Sketches of, Nature, vol. 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 FavOm 
Expedition of the Am. Museum of Nat. History, Science, March 29, 1907. 

Note. Since the four succeeding chapters deal with the Evolution 
Theory, it maybe 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 Theon,', but it is not best to lake 
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. 1. This to 
be followed by Wallace's Darwinism, and, thereafter, the Origin of Species 


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 Osborn's From the Greeks to Darwin. 


General: Romanes, Darwin and x^fter 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, Ergebnisse 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. 


Lamarck: Packard, Lamarck, the Founder of Evolution, His Life 
and Work, with Translations of his Writings on Organic Evolution, 1901; 
Lamarck's Philosophie Zoologique, 1809. Recherches sur 1' 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 /. 
Entivickelnngsmechanik, vol. 8, 1899. 

Darwin's Theory (For biographical references to Darwin see below 


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, /oc, a7. Sexual Selection: Darwin, The Descent 
of Man, new ed., 1892. Inadequacy of 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. 


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, Bericht iiber die Feier des 70 Geburts- 
tages von August Weismann, 1905, 2 portraits. 

Mutation-Theory of De Vries: Die Mutations-Theorie, 1901; 
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 0} Arts and Science, Universal Exposition, St. Louis, 1904; 
Davenport, Evolution without Mutation, Journ. Exp. ZooL, April, 1905. 


For early phases of Evolutionary thought consult Osborn, From the 
Greeks to Darwin, 1894, and Clodd, Pioneers of Evolution, 1807. Suarez 
and the Doctrine of Special Creation: Huxley, in Mr. Darwin's 
Critics, Cont. Rev., p. 187, reprinted in Critiques and .\ddresses, 1873. 
Buffon: In Packard's Life of Lamarck, chapter 13. E. Darwin: 
Krause's Life of E. Darwin translated into English, 1870; Packard, he. 
cit. Goethe: Die Idee dcr Pflanzenmetamorphose bei WollT uiid In'i 
Goethe, Kirchoff, 1867; Goethe's Die Metamorphose der Pflanzen, i7qo. 
Oken: His Elements of Physiophilosophy, Ray Soc, 1847. Cuvier and 
St. Hilaire: Perrier, La Philosophic Zoologiciue 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, 


published in the Trans. Linnccan Soc. for 1858, were reprinted in the Fop. 
Sci. Mo., vol. 60, 1901. Darwin: Personality and biography (For refer- 
ences 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 Darwinian 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 
Theor\^ of Natural Selection, 1896. Wallace: My Life, 2 vols., 1905; 
The Critic, Oct., 1905. Huxley: Lifeand Letters by his son, 1901; Nu- 
merous sketches at the time of his death, 1895, in Nature, Nineteenth Cen- 
tury, Pop. Sci. Mo., etc., etc. Haeckel: His Life and Work by Bolsche, 


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. Kept. 
Smithson. Inst., 1894; Marine Biolog. Station at Naples, Harper's Mag., 
1901; The Century, vol. 10 (Emily Nunn Whitman); Williams, A 
History of Science, vol. V, chapter V, 1904; Am. Nat., vol. 31, 1897; 
Pop. Sci. Mo., vol. 54, 1899; ibid., vol. 59, 190 1. Woods Holl Station — A 
Marine University, Ann. Kept. Smithson. Inst., 1902. 



Abiogenesis, 277 

Acc[uired characters, inheritance of, 

314; Weismann on, 308 
Agassiz, essay on classification, 137; 

agreement of embryological stages 

and the fossil record, 334; fossil 

fishes, 334; portrait, 334 
Aldrovandi, 115 
Alternative inheritance, 316 
Am})himixis, the source of variations, 


Anatomical sketches, the earliest, 32; 
from \'esalius, 31, t,;^ 

Anatomical studies, recent tenden- 
cies of, 442 

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, loq; 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, 

Animal behavior, studies of, 441 

Animal kingdom of Cuvier, 133 

Aquinas, St. Thomas, on creation, 

Arcana Naturae, of Leeuwenhoek, 

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, 
Arrest of inquiry, effect of, 17 
Augustine, St., on creation, 409 
Authority declared the source of 
knowledge, 18 



Bacteria, discovery of, 276; disease- 
producing, 300; and antiseptic 
surgery, 302; nitrifying, oi the 
soil, 303 

Bacteriology, development of, 276 

Bacr, \'on, and the rise of embr}-ol- 
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; jjortrait, 227; 
tragic fate, 228; university career, 

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; i)ortrait, 1S4 

Berengarius, 26 

Bernard, Claude, in physiology, 190; 
personality, 191; portrait, 10 1 

Biblia Natunc 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, 17c; 
writings, 170; successes of, 170 

Binomial nomenclature of Linna-us, 

Biological facts, application of, 443 

Biological laboratories, establish- 
nu-nt and maintenance of. 445; 
the station at Naples, 444; picture 
of, 445; the Woods Holl station, 

Biological periodicals, 446 
Biological progress, continuity of, 

434; atmosphere engendered by. 



448; from Linnaeus to Darwin, 

Biology, defined, 4; domain of, 4, 5; 
epochs of, 20; progress of, 3, 5; 
applied, 443 

Boerhaave, quoted, 71, 72; and 
Linnseus, 122 

Bois-Reymond, Du, 189; portrait, 

Bones, fossil, 322, 324 

Bonnet, and emboitement, 208; op- 
position to Wolff, 211; portrait, 

Books, the notable, of biology, 435 

Brown, Robert, discovers the nu- 
cleus in plant-cells, 243 

Buckland, 324 

Buckle, on Bichat, 166, 167 

Buffon, 129,411; portrait, 412; po- 
sition in evolution, 412 

Ca;salpinus, on the circulation, 50 

Cajal, Ramon y, 176; portrait, 176 

Camper, anatomical work of, 143; 
portrait, 144 

Carpenter, quoted, 170 

Carpi, the anatomist, 26 

Castle, experiments on inheritance, 

Catastrophism, theory of, Cuvier, 
326; Lyell on, 331 

Caulkins, on protozoa, 109 

Cell, definition of, 258; diagram of, 
257; earliest known pictures of, 
238, 239; in heredity, 257 

Cell-lineage, 234, 442 

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; 
vague foreshado wings of, 237 

Child, studies on regulation, 440 

Chromosomes, 254, 312 

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, 137-138 

Cohn, portrait, 271 

Color, in evolution, 386 

Columbus, on the circulation, 50 

Comparative anatomy, rise of, 141- 
165; becomes experimental, 165 

Cope, in comparative anatomy, 165; 
portrait, 336; important work in 
palaeontology, 337, 437 

Creation, Aquinas on, 409; St. 
Augustine on, 408; special, 410; 
evolution the method of, 348 

Cuvier, birth and early education, 
149; and catastrophism, 326; 
comprehensiveness of mind, 154;- 
correlation of parts, 133; debate 
with St. Hilaire, 416; domestic 
life, 155; forerunners of, 143; 
founds comparative anatomy, 154; - 
founder of vertebrate palaeontol- 
ogy, 325; his four branches of the 
animal kingdom, 132; goes to 
Paris, 151; life at the seashore, 
150; opposition to Lamarck, 414; 
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, 427; factors 
of evolution, 380; habits of work, 
426; home life, 423; at Downs, 
426; ill health, 426; naturalist on 
the Beagle, 425; natural selection, 
383 ; opens note-book on the origin 
of species, 426; personality, 422; 
portraits, 381, 423; parallelism in 
thought with Wallace, 427; pub- 
lication of the Origin of Species, 
429; his other works, 391, 429; 
theory of pangenesis, 306; varia- 
tion in nature, 382; the original 
drafts of his theory sent by 
Hooker and Lyell to the Linneean 
Society, 420-422; working hours, 
426; summary of his theor}', 405 

Darwin, Erasmus, 413; portrait, 

Darwinism and Lamarckism con- 
fused, 391; not the same as or- 
ganic evolution, 347 
Davenport, experiments, 319 
Deluge, and the deposit of fossils, 




De Vrics, mutation theory of, 402; 

j)ortrait, 403; summary, 406 
Dufour, Leon, on insect anatomy, 

Dujardin, 250, 262; discovers sar- 

code, 250, 266; portrait, 265; 

writings, 264 

Edwards, H. Milne-, 157; portrait, 

Ehrenberg, 106, 107; portrait, loS 
Embryological record, interpretation 

of, 22Q 

Embryology, Von Bacr and the rise 
of, IQ4-236; experimental, 2^2; 
gill-clefts and other rudimentary 
organs in embryos, 361; theoret- 
ical, 235 

Epochs in biological history, 20 

Evolution, doctrine of, generalities 
regarding, 345; controversies re- 
garding the factors, 346, 369; fac- 
tors of, 368; efifect on embryology, 
225; on palaeontology, 332; na- 
ture of the question regarding, 
348; a historical question, 348; 
the historical method in, 348; 
sweep of, 366; one of the greatest 
acquisitions of human knowledge, 
366; predictions verified, 367; 
theories of, 369; Lamarck, 369; 
Darwin, 386; Weismann, 392; 
De \'ries, 402; summary of evo- 
lution theories, 404; vagueness 
regarding, 346 

Evolutionary series, 35 1 ; shells, 35 1 ; 
horses, 354 

Evolutionary thought, rise of, 407- 
433 ; views of certain fathers of the 
church, 408 

Experimental observation, intro- 
duced by Harvey, 39-53 

Experimental work in biology, 439 

Fa])rica, of Vesalius, 30 

Fabricius, Harvey's teacher, 41; 

portrait, 43 
Factors of evolution, 369 
Fallopius, 36; portrait, 37 
Flood, fossils ascribed to, 323 
Fossil life, the science of, 320-341; 
bones, 322, 325; horses in Amer- 
ica, 355; collections in New 

Haven, ^^^\ in Xew York, ^^^y,; 
man, 340, 364; Neanderthal skull, 
365; ape-like man, 3O4 

Fossil remains an index to j)ast his- 
tory, 329 

Fossils, arrangement in strata, 328; 
ascribed to the flo<jd, 323; their 
comparison with living animals, 
324; from the Fayum district, 341 ; 
method of collecting, 340; nature 
of, 322; determination of, bv 
Cuvier, 325; Da \'inci, 322; 
Steno, 322; strange views regard- 
ing, 320 

Galen, 23, 180; portrait, 25 

Galton, law of ancestral inheritance, 
318; portrait, 317 

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, 393; 
complexity of, 395; the hereditary 
substance, 311; union of germ- 
plasms the source of variations, 

Germ -theory of disease, 293 

Germinal continuity, 224, 308; doc- 
trine of, 224, 311, 393 

Germinal elements, 305 

Germinal selection, 397 

Germinal substance, 310 

Gesner, 112; personality, 113; por- 
trait, 114; natural history of, 113 

Gill-clefts in embryos, 361 

Goodsir, 174 

Grew, work of, 56 


Haeckel, 431; portrait, 432 
Haller, fiber-theory, 242; opposition 
to WollT, 211; in j)hysiology, 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, 
ic)8; embryological treatise, 109, 
200; frontispiece from his genera- 
tion of aninials (1651), 201; in- 
tluence of, 52; introduces exper- 



imental method, 47; at Padua, 41; 
period in physiology, 180; per- 
sonal appearance and cjualities, 
42, 44, 45; portrait, 44; pred- 
ecessors of, 48; ciucstion as to 
his originality, 46; his teacher, 43; 
writings, 45 

Heredity, 305; a cellular study, 257; 
according to Darwin, 307; Weis- 
niann, 309; application of statis- 
tics to, 314; inheritance of ac- 
quired characters, 314; steps in 
advance of knowledge of, 308 

Hertwig, Oskar, portrait, 231; ser- 
vice in embryology, 232; Rich- 
ard, quoted, 125 

Hilaire, St., portrait, 416; see St. 

His, Wilhelm, 232; portrait, 233 

Histology, birth of, 166-178; Bichat 
its founder, 170; normal and 
pathological, 172; text-books of, 

Hooke, Robert, 55; his microscope 
illustrated, 55 

Hooker, letter on the work of Dar- 
win and Wallace, 420-422 

Horse, evolution of, 354 

Human ancestry, links in, 364, 365 

Human body, evolution of, 363 

Human fossils, 340, 364 

Hunter, John, 144; portrait, 145 

Huxley, in comparative anatomy, 
161; influence on biology, 430; in 
palaeontology, 335; portrait, 430 

Inheritance, alternative, Mendel, 
316; ancestral, 318; Darwin's 
theory of, 306; material basis of, 
31 1-3 13; nature of, 305 

Inheritance of acquired characters, 
314; Lamarck on, 377; Weis- 
mann on, 398 

Inquiry, the arrest of, 17 

Insects, anatomy of, Dufour, 106; 
Malpighi, 63; illustration, 65; 
Newport, 100; Leydig, 102; Straus- 
Diirckheim, 96; Swammerdam, 
70, 75; illustration, 76; theology 
of, 91 

Jardin du Roi changed to Jardin des 
Plantes, 372 

Jennings, on animal behavior, 109^ 

Jonston, 114 


Klein, 118 

Koch, Robert, discoveries of, 300; 

portrait, 301 
Koelliker, in embryology, 224; in 

histology, 171; portrait, 173 
Kowalevsky, in embryology, 224; 

portrait, 225 

Lacaze-Duthiers, 158; portrait, 159 
Lamarck, changes from botany to 
zoology, 372; compared with 
Cuvier, 327; education, 371; first 
announcement of his evolutionary 
views, 375; forerunners of, 411; 
first use of a genealogical tree, 131 ; 
founds invertebrate palaeontology, 
326; on heredity, 377; laws of 
evolution, 376; military experi- 
ence, 370; opposition to, 414; 
Philosophic Zoologique, 375 ; por- 
trait, 373; position in science, 132; 
salient points in his theory, 378; 
his theory of evolution, 374; com- 
pared with that of Darwin, 390, 
391; time and favorable condi- 
tions, 378; use and disuse, 374 
Leeuwenhoek, 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, 83; theoreti- 
cal views, 86 
Leibnitz, 208 

Leidy in palaeontology, 337 
Lesser's theolog)' of insects, 91 
Leuckart, 136; portrait, 136 
Leydig, 102; anatomy of insects,, 
102; in histolog}', 175; portrait, 

Linnaean system, reform of, 130-138 

Linnaeus, 1 1 8-1 30; binomial nomen- 
clature, 127; his especial service, 
126; features of his work, 127, 
128; his idea of species, 128, 129; 



influence on natural history, 125; 
personal appearance, 125; i)er- 
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, I 27; 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- 
ogX) SS"^' letter on Darwin and 
Wallace, 420-422; portrait, 331 

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 


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, 364; evolution of, 

363; fossil, 340, 364 
Marsh, O. C, portrait, 337 
Meckel, J. Fr., 162; portrait, 162 
Men, of biology, 7, 8; the foremost, 

437; of science, 7 
Mendel, 315; alternative inheritance, 
316; law of, 315; purity of the 
germ-cells, 316; portrait, 315; 
rank of Mendel's discovery, 316, 


Microscope, Hooke's, Fig. of, 55; 
Leeuwenhoek's, 81, Figs, of, 82, 8^ 

Microscopic observation, introduc- 
tion of, 54; of Hooke, >)y, Grew, 

55; Ehrenberg, 106; Malpighi, 
66, 67; Leeuwenhoek, 81, 84, 85, 

Microsco])ists, the ])ionc-er, 54 
Middle Ages, a renKjlding i)eriod, 

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 


Xageli, portrait, 26S 

Naples, biological station at, 446; 
picture of, 445 

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, 383; discovery of, 
427; Darwin and Wallace on, 429; 
extension of, by Weismann, 3()7; 
illustrations of, 384; inadecjuacy 
of, 389 

Nature, continuity of, 367; return 
to, 19; renewal of observation, lu 

Naturphilosophie, school of, 160 

Neanderthal skull, 365 

Needham, experiments on sj)onta- 
neous generation, 281 

Neo-Lamarckism, 380 

Newport, on insect anatomy, 100 

Nineteenth century, summary of dis- 
coveries in, 3 

Nomenclature of biology, 126, 127 

Nucleus, discovery of, by Brown, 
243; division of, 256, 313 

Observation, arrest of, 17; renewal 
of, 19; in anatomy, 26; and e.\- 
periment the method of science, 

22, 39 
Oken, on cells, 241; ])ortrait, i()0 
Omne vivum ex ovo, 200 
Omnis cellula e cellula, 30Q 
Organic evolution, iloctrine of, 345- 
367; influence of, on embryology, 
22s; throrics of. 368-40^: rise of 



evolutionary thought, 407-433; 
sweep of the doctrine of, 366 
Osborn, quoted, 10, 364, 410; in 
paljEontology, 339 

Palaeontology, Cuvier founds verte- 
brate, 325; of the Fayum district, 
341; Lamarck founder of inverte- 
brate, 326; Agassiz, 332; Cope, 
337; Huxley, 335; Lyell, 330; 
Marsh, 337; Osborn, 339; Owen, 
■ 332; William Smith, 328; steps 
in the rise of, 329 

Pander, and the germ-laver theorv, 

Pangenesis, Darwin's theory of, 306 

Pasteur, on fermentation, 294; 
spontaneous generation, 288; in- 
oculation for hydrophobia, 299; 
investigation of microbes, 298; 
personality, 296; portrait, 295; 
his supreme service, 299; venera- 
tion of, 294 

Pasteur Institute, foundation of , 299; 
work of, 300 

Pearson, Carl, and ancestral inher- 
itance, 318 

Philosophic Anatomique of St. Hi- 
laire, 416 

Philosophic Zoologique of Lamarck, 

Physiologus, the sacred natural his- 

torv, 110-112 

Physiology, of the ancients, 179; 
rise of, 179-194; period of Har- 
vey, 180; of Haller, 181; of J. 
Miiller, 184; great influence of 
Miiller, 185; after Muller, 188 

Pithecanthropus erectus, 341, 360 

Pliny, portrait, 16 

Pouchet, on spontaneous generation, 

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, 437 

in embryology, 232 
Redi, earliest experiments on the 

generation of life, 279; portrait, 

Remak, in embryology, 223 
Roesel, on insects, 95; portrait, 97 

Sarcode and protoplasm, 273, 275 

Scala Naturae, 131 

Scale of being, 131 

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, 352, 353 
Siebold, Von, 134, 135; portrait, 135 
Silkworm, Malpighi on, 63; Pasteur 

on, 299 
Smith, Wm., in geology, 328 
Spallanzani, experiments on genera- 
tion, 282; portrait, 283 
Special creation, theory of, 410 
Species, Ray, 117; Linnaeus, 129", 
are they fixed in nature, 350; or- 
igin of, 350-364 
Spencer, 418; his views on evolution 

in 1852, 419 
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-Durckheim, his monograph, 
96; illustrations from, loi 

Suarez, and the theory of special 
creation, 410 

Swammerdam, his Biblia Natune, 
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 Malpighi 
and Leeuwenhoek, 87 

System, Linnajan, reform of, 130- 

Systema Naturae, of Linnaeus, 121, 



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, 



Variation, of animals, in a state of 
nature, 382 ; origin of, according 
to Weismann, 396 

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; pred- 
ecessors of, 26; especial service 
of, 37; sketches from his works, 

31. 33^ 34, 49 
Vicq d'Azyr, 146; portrait, 147 

X'inci, Leonardo da, and fossils, 322 

\'irchow, and germinal continuity, 

225; in histology, 174; portrait, 

Vries, Hugo de, his mutation theory, 
403; portrait, 403; summary of 
theory, 406 


Wallace, and Darwin, 420; his ac- 
count of the conditions under 
which his theory originated, 427; 
portrait, 428; writings, 427 

Weismann, the man, 399; (juotation 
from autobiography, 401; per- 
sonal qualities, 399; portrait, 400; 
his theory of the gcrm-j)lasm, 392- 
399; summary oi his theory, 405 

Whitney collection of fossil horses, 

Willoughby, his connection with 

Ray, 1 15 

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, ^t,S<; por- 
trait, 339 


A- & M. OUL.L.II.GE. 


By Prof. Vernon L. Kellogg, of Lclajul Stanlord Iniver.sity 
Author of "American Insects," etc. 395 pp. and index. Svo. 
$2.00 net; by mail, $2.15. 

A simple and concise discussion for the educated lajnnan of 
present-day scientific criticism of the Darwinian selection 
theories, together with concise accounts of the other nK)r(' im- 
portant proposed auxiliary and alternative theories of sjx'cies- 
forming. With special notes and exact references to original 
sources and to the author's own ob.servations and experiments. 

"Its value cannot be overestimated. A book the student must have at 
hand at all times, and it take.s the place of a whole library. No other 
writer has attempted to gather together the scattered literature of thi.'^ 
vast subject, and none has subjected this literature to such unifonnly 
trenchant and uniformly kindly criticism. Pledged to no theory of his 
own, and an investigator of the first rank, and master of a clear and force- 
ful literary style. Professor Kellogg is especially well fitted to do justice 
to the many phases of present-day Darwinism." — D.wid St.\kk Johuan 
in The Dial. 

"May be unhe.sitatingly recommended to the student of biology as well 
as to the non-professional or even non-biological reader of intelligence . . . 
gives a full, concise, fair and very readable exposition of the present status 
of evolution." — The Independent. 

"Can write in English as brightly and as clearly as tlie old-time French- 
men ... a book that the ordinary reader can read with thorough enjoy- 
ment and understanding and that the .specialist can turn to with profit 
as well ... in his text he explains the controversy so that the i>laiii man 
may under .stand it, while in the notes lie adduces the evidence that the 
specialist requires. The whole matter is thoroughly digeste<l and put in 
an absolutely intelligible manner ... a brilliant b(jok that deserves gen- 
eral attention." — Sew York Sun. 

"The balance-.sheet of Darwinism is struck in this work . . . the attack 
and the of Darwinism, well summarized ... the value of this 
book lies in its summing up of the Darwinian iloctrines as tliey have been 
modified or verified down to date." — Literary Diiiest. 

*** If the reader will send his name and addre.-<s, the puhlisliors will semi, 
from time to time, information regarding tlieir new books. 

H E N R Y II O L T A .\ D C U M i* A N V 


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By A. L. Kimball, Professor in Amherst College. {In 


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By Ira Remsen, President of the Johns Hopkins Uni- 

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UCTXIPV UOI T X/ Cf^ 34 West 33(1 St., New York 
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In the hope of doing something toward furnishing a series where 
the nature- lover can surely find a readable book of high authority, 
the publishers of the American Science Series have begun the publi- 
cation of the American Nature Series. It is the intention that in its 
own way, the new series shall stand on a par with its famous prede- 

The primary object of the new series is to answer questions 
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The books so far publisht in this section are: 

FISHES, by David Starr Jordan, President of the Leland Stanford 
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AMERICAN INSECTS, by Yerxox L. Kellogg, Professor in the 
Leland Stanford Junior University. $5.00 net; carriage extra. 

Arranged for are : 

SEEDLESS PLANTS, by George T. Moore, Head of Department 
of Botanj", Marine Biological Laboratory, assisted bj- other spe- 

RiA>r, Chief of the United States Biological Survey. 

BIRDS OF THE WORLD. A popular account by Fraxk H. 
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Union, President Biological Society of Washington, etc., etc., 


with Chapter on Anatomy of Birds by EiiEnERic A. Licas^ 
Chief Curator Brooklyn Museum of Arts and Sciences, and edited 
by RoBEUT RiDGWAY, Curator of Birds, U. S. National .Museum. 

REPTILES AND BATRACHIANS, by Lkonharh Stejnegek, Cura- 
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Section B. A Shorter Natural History, mainly by the Authors 
of Section A, preserving its popular character, its proportional treat- 
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fullness. Size not yet determined. 


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Already publisht : 
FERNS, by Campuell E. Waters, of Johns Hopkins University. 

8vo, pp. xi+362. $3.00 net; by mail, $3.30. 

Section B. Identification Books — 

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Already publisht : 
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all Nature. 8vo. 6gx8i in. 

Already publisht : 

Curator of Birds in the New York Zool(>gical Park. Svo, 496 pp. 

$3.50 net; by mail, $3.80. 

Arranged for : 

Kki.i.ogg, Professor in the Iceland Stanford Junior University. 

the U. S. Bureau of Fisheries. 

A M li R I C A X X A T U R E SERIES (Continued) 


How to propagate, develop and care for the plants and animals. 
The volumes in this group cover such a range of subjects that it is 
impracticable to make them of uniform size. 

Already publisht : 

NATURE AND HEALTH, by Edward Ctrtis, Professor Emeritus 
in the College of Physicians and Surgeons. 12mo. $1.25 net; 
by mail, .$1.37. 
Arranged for : 

PHOTOGRAPHING NATURE, by E. R. Sanborn, Photographer 
of the Xew York Zoological Park. 

THE SHELLFISH INDUSTRIES, by James L. Kellogg, Professor 
in Williams College. 

CHEMISTRY OF DAILY LIFE, by Hexrv P. Talbot, Professor 
of Chemistry in the Massachusetts Institute of Technology. 

DOMESTIC ANIMALS, by William H. Brewer, Professor Emeri- 
tus in Yale University. 


B. E. Ferxow, Professor of Forestry in the University of 


This division will include a wide range of writings not rigidly 
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Large 12mo. 51x81 in. 

FISH STORIES, by David Starr Jordan and Charles F. Holder. 
HORSE TALK, By William H. Brewer. 
BIRD NOTES, by C. W. Beebe. 
INSECT STORIES, by Vernon L. Kellogg. 


A Series of volumes by President Jordan, of Stanford Univer- 
sity, and Professors Brooks of Johns Hopkins, Lull of Yale, Thom- 
son of Aberdeen, Przibram of Austria, zcr Strassen of Germany, 
and others. Edited by Professor Kellogg of Leland Stanford. 12mo. 
5|xTi in. 


June, '08.