SOME ASPECTS OF MAMMALIAN 

 FERTILIZATION 



M. C. CHANG: WORCESTER FOUNDATION FOR EXPERIMENTAL 

 BIOLOGY, SHREWSBURY, MASSACHUSETTS, AND DEPARTMENT OF 

 BIOLOGY, BOSTON UNIVERSITY 



Brief and concise historical accounts of the study of fertiUza- 

 tion have been written by LilHe ( 1923 ) and Austin ( 1953 ) . The 

 Study of fertihzation is a classical subject but lower organisms, 

 especially marine species, were used by early investigators and 

 by most active workers at the present time. In the lower forms, 

 fertilization takes place externally, thus modern physiological, 

 immunological, biochemical, and biophysical techniques can be 

 employed experimentally without much difficulty. In the higher 

 animals, fertilization occurs internally, i.e., in the Fallopian tubes. 

 This makes the experimental analysis of the basic mechanisms of 

 mammalian fertilization very difficult. Moreover, it seems that in 

 the higher animals, owing perhaps to their fertilization in vivo, 

 the process of fertilization is predominantly controlled by internal 

 factors. During the past fifty years, a great deal has been learned 

 about the preparation for fertilization in the mammalian species, 

 such as the growth, maturation, release, and transportation of 

 gametes before fertilization and the morphology and physiology 

 of zygotes after fertilization, but very little is known about the 

 process of fertilization, per se, or the fertilization reaction in mam- 

 mals and the basic mechanisms involved. This is due mainly to 

 the fact that there is no simple procedure for fertilizing mamma- 

 lian eggs in vitro. I shall review here certain facts and some prob- 

 lems involved in the study of mammalian fertilization. The pre- 

 liminaries to fertilization are reviewed by Austin and Bishop in 

 this volume. 



109 



