CHAPTER V 



SPERMATOGENESIS— INSEMINATION 



" Denlque per maria ao montis fluviosque rapacis 

 Frondiferasque domos avium camposqae virentis. 

 Omnibus incutiens blandum per pectora amorem 

 EfEcis ut cupide geueratim saacla propagent." 



— LUCEBTIUS. 



The spermatozoa, or reproductive cells of the male, were ob- 

 served as far back as tbe year 1677, when Hamm, who was a 

 pupil of Leeuwenhoek, directed the latter's attention to them. 

 Leeuwenhoek, however, did not understand the significance of 

 what he saw. 



Spallanzani ^ was the first to show that the presence of 

 spermatozoa in the semen was an essential factor in fertilisation, 

 since the filtered fluid was found to be impotent. Subsequently 

 Kolhker ^ discovered that the sperms arise from the cells of the 

 testis, and Barry ^ observed the conjugation of sperm and ovum 

 in the rabbit. 



Van Beneden's discovery that the nuclei of the conjugat- 

 ing cells — both ova and spermatozoa — contain only half the 

 number of chromosomes that they had originally has been 

 referred to in the preceding chapter, where the maturation 

 phenomena in the ovum have been briefly outlined * (p. 130). 

 The four products of division formed at the completion of re- 

 duction in the male differ from those in the female in that each 

 of them is a functional conjugating cell. Before describing the 

 reduction process in detail it will be well to give a short account 

 of the structure of the testis.^ 



^ Spallanzani, i)isscrte(«ons, English Tianslation, vol. ii., London, 1784. 



2 Kblliker, Beitrage zur Kcnntniss der OesoAlechtsvcrhdZtnisse, &c. , Berlin, 1841 . 



^ Barry (M.), " Spermatozoa observed within the MammiferousOvum,"i'At7. 

 Trans., 1843. 



* For accounts of the history of the chief discoveries relating to the 

 spermatozoa, fertilisation, &c., see Thomson, The Science of Life, London, 

 1899, and Geddes and Thomson, The Evolution of Sex, 2nd Edition, 

 London, 1901. 



° See Barry (D. T. ), " The Morphology of the Testis," Jour, of Anat. and 

 Pliys., vol. xliv., 1910. 



