ACTION OF THE MALE. 955 



tubuli seminiferi; constituting, like the analogous cells of other glands, the 

 essential elements of the spermatic apparatus. 1 These parent-cells are some- 

 times observed to contain but a single u vesicle of evolution," as shown at D ; 

 but more commonly three, four, six, or seven are to be seen within them (E). 

 When taken from a body recently dead, and examined without being treated 

 with water or any other agent, they are quite pellucid, and exhibit a delicate 

 contour, with perfectly homogeneous contents ; very speedily, however, a sort 

 of coagulation takes place within them, by which their contents are rendered 

 granular. Each of these "vesicles of evolution" gives origin to a spermato- 

 zoon, and to one only ; the earliest stages of its development have not yet been 

 distinctly made out, since it does not at first exhibit those sharp distinct con- 

 tours, dependent on its great refractive power, which afterwards distinguish it ; 

 but it is seen lying i^ the interior of the cell as a slight linear shadow, at 

 first partly hidden by the surrounding granules (Fig. 3, B), but afterwards 

 without any such obscuration. When the vesicle is completely matured, it 

 bursts, and gives exit to the contained spermatozoon, which, thenceforth, in the 

 Mammalia, usually moves freely in the spermatic fluid ; in Birds, however, it is 

 more common for the parent-cells to retain the vesicles of evolution during the 

 development of the Spermatozoa within the latter ; so that when these set free 

 the Spermatozoa, they are still enveloped by the parent-cell. In this condition 

 they have a tendency to aggregation in bundles; and these bundles are finally 

 liberated by the rupture of the parent-cell, after which the individual sperma- 

 tozoa separate from one another. Such bundles may be occasionally seen in 

 the Human semen. That the Spermatozoa are the essential elements of the 

 spermatic fluid, may be reasonably inferred from several considerations. There 

 are some cases in which the " liquor seminis" is altogether absent, so that they 

 constitute the sole element of the semen ; whilst, on the other hand, they are 

 never wanting in the semen of animals capable of procreation ; but are absent, 

 or imperfectly developed, in the semen of hybrids, which are nearly or entirely 

 sterile. Moreover, we have every reason to believe that, in the higher animals, 

 the absolute contact of the spermatozoa with the ovum is requisite for its fecun- 

 dation ; whilst, on the other hand, if the spermatozoa be carefully removed from 

 the liquor seminis by filtration, the latter is found to be entirely destitute of 

 fertilizing power. 2 It is interesting to remark that the perfectly developed 

 spermatozoa possess the same chemical composition with the epithelial tissues in 

 general. 3 



960. The power of procreation does not usually exist in the Human Male, 

 until the age of from 14 to 16 years ; and it may be considered probable that 

 no Spermatozoa are produced until that period, although a fluid is secreted by 

 the testes. At this epoch, which is ordinarily designated as that of Puberty, a 

 considerable change takes place in the bodily constitution : the sexual organs 

 undergo a much-increased development; various parts of the surface, especially 

 the chin and the pubes, become covered with hair; the larynx enlarges, and 

 the voice becomes lower in pitch, as well as rougher and more powerful; and 

 new feelings and desires are awakened in the mind. Instances, however, are 

 by no means rare, in which these changes take place at a much earlier period; 

 the full development of the generative organs, with manifestations of the sexual 



1 In the Hydra and other Zoophytes, such cells are found imbedded in the general 

 substance of the body, instead of being developed within a special organ. 



2 This point has been completely established by the researches of Mr. Newport ("Phil. 

 Trans.," 1851), who has repeated and confirmed the experimental results previously ob- 

 tained by Spallanzani and by Prevost and Dumas. 



8 For the latest researches on the development, &c., of the Spermatozoa, see the elabo- 

 rate Article "Semen," in the "Cyclop, of Anat. and Physiol.," by Drs. Wagner and 

 Leuckardt. 



