Front matter
1*
A
LABORATORY TEXT-BOOK OF EMBRYOLOGY
Preface
The accompanying volume is designed primarily for the use of students taking a practical laboratory course in embryology. It is intended to direct the student’s attention to actual, original observations, to be made by himself, and to aid him in drawing correct conclusions from those observations. By this plan, the student repeats and uses the actual methods by which embryological science has been built. If he pursues such a course diligently, he will be able at the end of it to say that he knows of his own knowledge. To attain this result is the ideal of laboratory education.
In preparing the new edition, advantage has been taken of the experience gained with the use of the book by the author’s classes, and of valuable suggestions from many friends. The work has been so extensively revised that it may be described as almost a new book. Chapters III to VI have been entirely recast and rearranged so as to conform to the chronological order of development, an arrangement which it is believed most readers will prefer to that adopted in the original edition. Chapter II, on the early development of mammals, has been considerably expanded; not with the object of giving a comprehensive treatment of the subject, but rather with the intention of aiding the student to get, in connection with his laboratory work, a connected story in his mind of the development of the principal organs and systems of the body. Some new sections will be found also in Chapter I. A considerable number of the figures are replaced by new ones. The total number of illustrations has increased from 218 to 262. With these changes it is hoped that the second edition will deserve a continuance of the favor shown to the original issue.
The author takes much pleasure in acknowledging gratefully the invaluable assistance afforded him by members of his laboratory staff, and wishes to call attention especially to the very admirable original illustrations which have been furnished especially for the book by Drs. J. L. Bremer, F. P. Johnson, F. T. Lewis,
R. E. Scammon, and F. W. Thyng. Special mention must be made also of the figures from models made by Messrs. W. W. Behlow, G. C. Coe, L. M. Ferguson, C. A. Hedblom, and A. R. Kilgore, students in the embryological course at
the Harvard Medical School.
A large majority of the illustrations are from the Harvard Embryological Collection, without which this work would not have been possible. The author requests those who use this book to communicate to him any suggestions, which their experience may lead to, for improving it.
Charles S. Minot.
Harv.ard Medical School, May 28, 1910.
vii
Contents
PAGE
Chapter I. — General Conceptions, i
The Segmented Animals. Metamerism, , . 2
The Vertebrate Type of Structure, 2
The Principal Modifications of the Vertebrate Type, 7
Definition of Anlage, 9
A Summary of Embryological Development, 10
Comparison of Larval and Embryonic Types of Development, 16
Germ-layers, 18
The Relations of Surface to Mass, 20
Classification of Glands, 23
The Law of Unequal Growth, 24 ■
Germ-cells, 25
Sex, 27
The Theory of Heredity, 28
The Law of Recapitulation, 29
Arrest of Development, 31
Chapter II. — The Early Development of Mammals, 33 The Spermatozoon, 33
The Fully Grown Ovum Before Maturation, 34
Ovulation, 35
The Maturation of the Ovum, 36
Impregnation of the Ovum, 38
Segmentation of the Ovum, 42
The Blastodermic Vesicle, 45
The Embryonic Shield, 47
Growth of the Embryo and Separation of the Yolk, 49
Origin of the Mesoderm, 51
The Primitive Axis, 52
The Notochordal Canal, 53
The Notochord, 55
The Ultimate Fate of the Notochord, 56
The Archenteron, 57
The Oral and Anal Plates, 58
The Digestive Canal, 59
The Yolk-sac, 63
The Origin of the Nervous System, 67
The Structure of the Medullary Canal, 69
Origin of Nerves, 72
IX
X
CONTENTS.
PAGE
The Spinal Cord and Brain, 73
Plakodes, 76
The Nasal Pits and Olfactory Nerves, 76
The Eye, 77
The Otocyst, 78
The Early History of the Mesoderm, 79
Somatopleure and Splanchnopleure, 82
The Embryonic Coelom, 84
The Mesenchyma, 89
The Origin of the Blood-vessels and Blood, 90
The Blood-corpuscles, 93
The Origin of the Heart, 96
The Germinal Area, . ' 96
The Main Vessels of the Area Vasculosa, 97
The Aortic System, 99
The Venous System, 102
The Lymphatic System, 105
The Liver, 107
The Pancreas, 107
The Excretory Organs, 108
The Urogenital Ducts, no
The Allantois, in
The Trophoderm, 114
The Chorion and Amnion, 117
Ch.<\pter III. — The Human Embryo, 118
Calculation of the Age of the Human Embryo, 118
The Classification of the Early Stages, 119
Hypothetical Development of the Blastodermic Vesicle in Primates, 122
Relations of the Embryo to the Uterus; the Two Stages, 124
Ovum of a Monkey in the Second Stage, 127
Human Embryo in the Second Stage, 128
The Embryo of a Gibbon in the Third Stage, 13 1
Human Embryo in th Eourth Stage with the Medullary Plate, 134
Human Embryo in the Fifth Stage with Open Medullary Groove, 136
Human Embryo in the Sixth Stage with Medullary Canal, 137
Human Embryo in the Seventh Stage with One Gill-cleft Showing Externally, 140
Human Embryo in the Eighth Stage with Two Gill-clefts Showing Externally, 141
Human Embryo in the Ninth Stage with Three Gill-clefts Showing Externally, 143
Human Embryo in the Tenth Stage with Four Gill-clefts Showing Externally, 146
Human Embryo in the Eleventh Stage with the Cervical Sinus in Formation, 147
Human Embryos of the Fourth Week to the Fourth Month, 148
Chapter IV. — Study of the Segmentation of the Ovum and of the Blastodermic \ esi- CLE IN Mammals, 160
The Maturation, Fertilization, and Segmentation of the Ovum in White Mice, 160
Method of 'Obtaining Blastodermic Vesicles from the Rabbit, 166
Ch.apter V. — Study of Young Chick Embryos, 174
Method of Obtaining Embryos, 174
CONTENTS.
XI
PAGE
Embryo Chick with Eight Segments (About Twenty-eight hours’ Incubation), 176
Embryo Chick with about Twenty-four Segments and Three Gill-clefts (About Forty-
six Hours’ Incubation), 197
Embryo Chick with Twenty-eight Segments, 199
The Study of Transverse Sections, 199
Horizontal Section, 214
Histological Differentiation of the Chick Embryo with Three Gill-clefts, 216
Chapter VI. — Study of Pig Embryos, 219 Methods of Obtaining Embryos, 219
The Making of Serial Sections, 220
Selection of the Planes of Section and the Stages for Practical Study, 220
The Study of the External Form, 221
Pig Embryo of 7.5 mm., 221
Pig Embryo of 10 mm., 223
Pig Embryo of 15 mm., 225
Pig Embryo of 20 mm., 226
Pig Embryo of 7.8 mm. General Anatomy, 228
Pig Embryo of 12 mm. General Anatomy, 231
Study of Transverse Sections, 261
Study of Sagittal Sections, 290
Study of Frontal Sections, 296
Frontal Section of the Umbilical Cord, 310
Transverse Sections 31 1
Sagittal Section, 322
Frontal Sections of the Head, 324
Chapter VII. — Study of the Uterus and the Fetal Appendages of Man, 339 Histology of the Uterus, 339
Menstruation, 339
The Pregnant Uterus: the Two Stages, 341
Human Uterus Three Months Pregnant, 343
Human Uterus Seven Months Pregnant, 345
Decidua Vera of the First Stage in Section, 346
Decidua Reflexa of the First Stage, 349
Decidua Vera and Chorion Laeve of the Second Stage, • 350
The Placenta in Situ, 352
Decidua Serotina at Seven Months, 357
The Human Placenta, 359
Histology of the Human Chorion, 363
The Chorion with Trophoderm, 364
The Chorionic Villi, 367
The Structure of the Amnion, 370
The Structure of the Human Yolk-sac, 375
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CONTENTS.
PAGE
Chapter VIII. — Methods, 377 Measuring Length of Embryos, 377
Dissection of Embryos, 377
Methods of Hardening and Preserving, 377
Preservation in Alcohol, 380
Directions for Imbedding Specimens to be Microtomed, 380
Method of Mounting Paraffin Sections, 381
Methods of Staining, 381
Methods of Reconstruction, 385
Directions for Orienting Serial Sections of Embryos, 388
Microtomes, 389
Index, 393
TEXT-BOOK OF EMBRYOLOGY.
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