HISTORICAL CONSIDERATIONS 213 



plasmic and nuclear, is effected, resulting in the initiation of normal 

 development. 



The biochemical and physiological factors which accomplish the union of 

 the haploid chromosome groups and the activation of the gametes are the 

 objectives of one of the main facets of embryological investigation today. 



B. Historical Considerations Concerning Gametic Fusion and Its 



Significance 



The use of the word "fertilization" in the sense of initiating development 

 and the idea of making fertile or fruitful, which the word arouses in one's 

 mind, reaches back to the dawn of recorded history. The concept of this 

 fruitfulness as being dependent upon the union of one sex cell with another 

 sex cell and of the fusion of the two to initiate the development of a new 

 individual originated in the nineteenth century. However, Leeuwenhoek, in 

 1683, appears to have been the first to advance the thesis that the egg must 

 be impregnated by a seminal animalcule (i.e., the sperm) in order to be- 

 come fruitful, but the real significance of this statement certainly was not 

 appreciated by him. 



Moreover, to Leeuwenhoek, the idea behind the penetration of the egg by 

 the seminal animalcula was to supply nourishment for the latter, which he 

 believed was the essential element in that it contained the preformed embryo 

 in an intangible way. That is, the sperm animalcule of the ram contains a 

 lamb, which does not assume the external appearance of one until it has 

 been nourished and grown in the uterus of the female (Cole, '30, pp. 57, 165). 

 It should be added parenthetically that actual presence of the little animalcules 

 as living entities had previously been called to Leeuwenhoek's attention in 

 1677 by a Mr. Ham (Cole, '30, p. 10). 



In the years that followed Leeuwenhoek the exact interpretation to be 

 applied to the seminal animalcules (sperm) was a matter of much debate. 

 Many maintained that they were parasites in the seminal fluid, the latter being 

 regarded as the essential fertilizing substance in the male semen. In 1827, 

 von Baer, who regarded the sperm as parasites, named them spermatozoa, 

 that is, parasitic animals in the spermatic fluid (Cole, '30, p. 28). Finally, 

 in the years from 1835-1841, Peltier, Wagner, Lallemand, and Kolliker, es- 

 tablished the non-parasitic nature of the sperm. Kolliker in 1841 traced their 

 origin from testicular tissue, and thus settled the argument once and for all 

 as to the true nature of the seminal animals or sperm. 



Various individuals have laid claim to the honor of being the first to de- 

 scribe the sperm's entry into the egg at fertilization, but the studies of Newport 

 and Bischoflf (1853, 1854) resulted in the first exact descriptions of the 

 process. (See Cole, '30, pp. 191-195.) Thus the general proposition set forth 

 by Leeuwenhoek 170 years earlier became an accepted fact, although the 



