AGE OF HUMAN EMBRYOS 417 



the injected fluid immediately ran out of the ruptured follicle. 

 In a few instances the fluid entered mature follicles, causing them 

 to become dense and finally to rupture when the vascular pressure 

 was continued for a sufficiently long period. This suggests at 

 least that a factor in fertilization is the rupture of a Graafian 

 vesicle, due to orgastic reaction in the uterus, tubes and ovaries 

 when copulation takes place immediately after menstruation. 

 At this time ovulation is most likely to occur in tower animals, 

 and all the facts indicate that the same is true in human beings. 

 It is known that in the rabbit, dog and pig there must be repeated 

 copulation in order to insure impregnation. A single mating 

 rarely suffices. Thus, for instance, according to Weysse,i^ only 

 three out of the nine sows became pregnant after being covered 

 but a single time. This would indicate that the fertilization 

 power of the sperm was of short duration, as Bryce and 

 Teacher seem to think is the case in human beings. 



According to Waldeyer^^ live spermatozoa were found in the 

 bitch eight days after copulation, and dead cells, that is motion- 

 less cells at the end of 17 days. Living moving spermatozoa 

 were found in a woman three days after death. Living sperm 

 cells were found in the Fallopian tube of a patient 9 days after 

 admission to the hospital and 3^ weeks after copulation. On the 

 other hand, spermatozoa have been found upon the surface of 

 the ovary of the rabbit and sow two hours after copulation. In 

 Waldeyer's opinion the power to fertilize remains as long as the 

 sperm cells retain normal motility, and there are no facts to deny 

 that human sperm has the power to fertilize over a week after 

 copulation. 



Spermatic cells of animals that emit them into water die in a 

 very short time if they are greatly diluted, and have a much 

 longer life if only a little water is added. Thus in fertilizing 

 trout eggs 'dry' sperm is used, while if the sperm is added to 

 water containing the eggs but few eggs are fertilized. This 



1^ Weysse, Arthur Wisswald 1894 The bhistodermic vesicle sus scrofa domes- 

 ticus. Proc. Amer. Acad. Arts and Sciences, vol. 30. 



1^ Waldeyer, W. 1906 Hertwig's Handbuch der Vergleich. und Exper. 

 Entwickelungslehre der Wirbeltiere. Bd. 1, Tl. 1, Erste Halfte. 



