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                                EMBRYOLOGY

                          THE BEGINNINGS OF LIFE


                    BY GERALD LEIGHTON, M.D., F.R.S.E.

             AUTHOR OF "THE GREATEST LIFE," "BRITISH SERPENTS"
                     "HUXLEY: HIS LIFE AND WORK," ETC.




                         LONDON: T. C. & E. C. JACK

                     67 LONG ACRE, W.C., AND EDINBURGH

                       NEW YORK: DODGE PUBLISHING CO.


                     *       *       *       *       *




                                 CONTENTS


  CHAP.                                                          PAGE

     I. THE CELL AND THE INDIVIDUAL                                 7

    II. PROBLEMS OF REPRODUCTION                                   15

   III. PROBLEMS OF REPRODUCTION (_continued_)                     23

    IV. THE MAKING OF A MAN                                        36

     V. FERTILISATION AND EARLY DEVELOPMENT                        47

    VI. EARLY DEVELOPMENT                                          53

   VII. THE BEGINNINGS OF THINGS                                   59

  VIII. THE BEGINNINGS OF THINGS (_continued_)                     62

    IX. THE BEGINNINGS OF THINGS (_continued_)                     66

     X. THE BEGINNINGS OF THINGS (_continued_)                     73

    XI. HOW THE EMBRYO IS NOURISHED                                78

   XII. RECAPITULATION                                             84

        BIBLIOGRAPHY                                               90

        INDEX                                                      91


                     *       *       *       *       *




                                 EMBRYOLOGY




                                 CHAPTER I

                        THE CELL AND THE INDIVIDUAL


What is Embryology, and what is its significance or interest to the
ordinary educated man and woman? The answer to the question is the
justification for the appearance of the following pages, and one may
regard it as a somewhat striking fact, that in the production of a
series of works of which this volume is one, those responsible for the
subjects should have deemed it advisable to include Embryology.

Embryology may be defined as that part of the science of Biology which
deals with the formation of a new individual or embryo. The definition
itself ought to be sufficient to explain the significance of the subject
for every one, because one can hardly conceive of any more profoundly
important knowledge than that which tells of the mode of origin, manner
of growth, and ultimate birth of an entirely new being. In the absence
of such accurate knowledge it is quite obvious that all one's ideas
concerning the manner in which the new individual is to be treated must
have a more or less haphazard, or at least empirical, basis. In fact
only when the science of Embryology, or the development of the
individual, becomes a part of the ordinary everyday mental equipment of
those who are responsible for bringing into the world new individuals,
and subsequently protecting and handling them, will it be reasonable to
expect that these new individuals are dealt with in the best possible
manner. In a word it is evident that education, using that term in the
very widest possible sense, can never be anything more than a blind
groping in the dark until those into whose hands it is entrusted realise
and know at least the most important fundamental facts concerning
development. It is lack of this kind of knowledge which has been
responsible for so much of the mistaken systems of the past in dealing
with the young, and it is the spread of this knowledge which alone is
the hope of better things in the future. Wherever knowledge is absent
superstition is rife, and in no sphere of life is this more painfully
obvious than in connection with the subject which we are about to study.
It would have been entirely impossible for many of the stupid and even
cruel methods of mental and physical treatment which have been meted out
to the young children in the past to have been tolerated for a moment
had this knowledge been available and sufficiently widespread.
Possessing it, a flood of light is thrown upon the fascinating and
otherwise obscure problems of heredity; and thus it lays open the pages
of the past for those who care to read them. Possessing it also it
throws upon the mental screen pictures of possibilities in the future
for all those who have eyes to see. So the study of Embryology links up
the past with the present and joins the present with the future. Is it
not, therefore, obvious that the study of such a subject means dealing
with problems the importance of which it is impossible to exaggerate;
problems which the parent, the teacher, the social reformer, the
politician, and the philanthropist will grapple with in vain unless they
call in science to their aid? Such is the meaning and significance of
the subject of our study.

In the widest sense of the word Embryology, therefore, deals with all
manner of living things, be they plant or animal. But since our purpose
here is to state, as far as possible in the space at our disposal, the
facts which are of particular importance in relation to the human
subject, we shall only glance at the rest of living creatures. A brief
look at them, however, is quite necessary in order to appreciate what
follows. Let