CHAPTER VI 



FERTILISATION 



" Although it be a known thing subscribed by all, that the foetus 

 assumes its origin 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 ooine the 

 chicken out of the egge." — Habvey. 



Although much progress has been effected, and many new 

 facts have been discovered, since Harvey wrote his famous dis- 

 sertation on " The EiBcient Cause of the Chicken," the actual 

 nature of the process whereby the ovum, after being discharged 

 from the ovary, is endowed with a new vitahty through union 

 with a spermatozoon, is a problem the solution of which is still 

 far from complete. 



In 1843 Martin Barry,^ as already mentioned, first observed 

 the union of the spermatozoon and ovum in the rabbit, and a 

 Uttle later Newport ^ recorded its occurrence in the frog ; but it 

 was not until the last quarter of the nineteenth century that 

 the significance of the process was reahsed. It was largely 

 through the work of Hertwig, Strasburger, and van Beneden 

 that most biologists came to beheve that the union of the nuclei 

 of the gametes was the essential act in the process of conjugation. 

 The more recent investigations of Boveri and others do not, 

 however, entirely support this conclusion. 



As aheady described, the head of the spermatozoon represents 

 the nucleus, and contains the chromatin material. When the 

 sperm penetrates into the substance of the ovum the tail be- 

 comes absorbed, but the head remains as the male pronucleus. 

 The matured nucleus of the ovum, or female pronucleus (the 

 two polar bodies having been discharged), passes towards the 



' Barry, " Spermatozoa Observed within the Mammiferons Ovum," Phil. 

 Trans., 1843. 



^ Newport, " On the Impregnation of the Ovum in the Amphibia," Phil. 

 Trans., 1851. 



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