THEORY OF FERTILIZATION. 



H7 



CHAPTER XII. 

 THEORY OF FERTILIZATION. 



tn his forty-ninth Exercitation on the "efficient cause of the 

 chicken," Harvey thus quaintly expresses what has always been, and 

 still is, a baffling problem : ' ' Although it be a known thing, subscribed 

 by all, that the foetus assumes its original and birth from the male and 

 female, and consequently that the egge is produced by the cock and 

 henne, and the chicken out of the egge, yet neither the schools of 

 physicians nor Aristotle's discerning brain have disclosed the manner 

 how the cock and its seed doth mint and coine the chicken out of the 

 egge." The old theories on the subject are more curious than profit- 

 able, a fact not to be wondered at since it is really only within the last 

 fifty years that the fundamental fact of the union of the sex-cells has 

 been observed. 



I. Old Theories of Fertilization. — (a) From Pythagoras and 

 Aristotle on to the "Ovists," of whom we have already spoken 

 (p. 81), numerous naturalists have held the opinion that the ovum was 

 the all-important element, which only required to be awakened to 

 development by contact with the male fluid or male elements. It 

 must be allowed that while ova may exceptionally develop without 

 sperms, the latter never come to anything apart from ova. This will 

 be less insisted on, however, when it is recognized that in realitv the 

 ovum is not so fairly comparable with the spermatazoon as with the 

 mother-sperm-cell. It must be allowed, too, that there is much to 

 warrant us in thinking of the sperm as an element which stimulates 

 the ovum to division; yet this will be recognized as only approximate 

 language, when the facts of the intimate nuclear union are fully 

 appreciated. 



(<$) In contrast to the above opinion, we find ingenious thinkers, so 

 widely separate in time as Democritus and Paracelsus, regarding the i 

 male fluid as very important — forestalling Buffon and Darwin — in fact, 

 in considering it in a sense an extract or concentrated essence of the 

 whole body. But it was only after the spermatozoa were themselves 

 detected that their importance became unduly exaggerated, in the 

 minds of those who seem almost to have been nicknamed " animal- 

 culists." It seems probable enough that Leeuwenhoek himself (1677) 

 saw the spermatozoon entering the ovum, — he at least said that he 

 did, — but that did not prevent him from ascribing to the male ele- 

 ments all the credit of development. This became, as we have seenj 



