CHAPTER V 



SPERMATOGENESIS— INSEMINATION 



" Semper enim partus duplici de semine constat." — Lucretius. 



The spermatozoa, or reproductive cells of the male, were observed 

 as far back as the 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 sper- 

 matozoa in the semen was an essential factor in fertilisation, since 

 the filtered fluid was found to be impotent. Subsequen,tly KoUiker^ 

 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 conjugating 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. 125). The four products of division 

 formed at the completion of reduction 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.^ 



This organ is enclosed within a fibrous capsule, the tunica 

 albuginea, which is very rich in lymphatics. It is covered by a 

 layer of serous epithelium reflected from the tunica vaginalis. 

 Posteriorly the capsule is prolonged into the interior of the testis 

 in the form of a mass of fibrous tissue (the mediastinum testis). 

 Certain other fibrous processes or trabeculte also project inwards 

 from the capsule, and divide the glandular substance into lobules. 

 The efferent ducts of the testis (vasa efferentia) open into a single 



' Spallanzani, Dissertations, English Translation, vol. ii., London, 1784. 



^ Kolliker, Beitrdge zur Kenntniss der Oeschlechtsverhaltnisse, etc., Berlin, 1841. 



' Barry (M.), "Spermatozoa observed within the Mammiferous Ovum," 

 Phil. Trans., 1843. 



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

 spermatozoa, fertilisation, etc., 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," Jotir. of Anat. and 

 Phys., vol. xliv., 1910. 



