THE SPERMATOZOA. 157 



simple cells, which, during their subsequent life, form sper- 

 matozoa within the passages of the female, as they would 

 have done within the organs in which the spermatic cells were 

 first formed, the requisite conditions being duly supplied. 



We will now touch upon the history of the development of 

 the spermatozoa, and will thus trace their kinship with the 

 cell. In the earlier stages of physiological science they were 

 regarded in the light of animalcule. At the present time 

 they are considered as epithelial cells, or, as Dr. O. W. 

 Holmes expresses it, are related to ciliated epithelium. 



They are, as has been before stated, the product of the 

 testes. The testicles are a couple of true glands, containing 

 the secreting elements in the form of complexly convoluted 

 tubules, — the spermatic tubes, or tubuli semeniferse. These 

 consist of a fibrous coat, internal to which is a basement 

 membrane surrounded by epithelium. The character of this 

 epithelium and the contents of these tubes vary with the age. 

 In boys and young animals the slender tubuli contain nothing 

 but minute, clear cells, the most external of which may be 

 regarded as epithelial cells. The spermatozoa are not found 

 in these tubes until puberty in man, and among some animals 

 are only developed at certain periods. The epithelium lining 

 the tubes is most distinct when spermatozoa are not being 

 found, but when the function of the gland is being actively 

 performed the tubes are seen to be entirely occupied by cells, 

 filled with nuclei, in which the spermatozoa are ultimately 

 developed. 



• The method of development is thus described by Todd and 

 Bowman : "The cells become detached from the basement 

 membrane, increase in size, and assume a more spherical form, 

 the contents at this time being entirely granules ; at length, 

 however, several clearer points or nuclei are seen in the inte- 

 rior of the cell, which is now passing down the tubule towards 

 the vas deferens, while it is succeeded behind by the formation 

 of new cells. The nuclei in the interior enlarge, and are 

 often seen to contain nucleoli. The parent cell having much 

 increased in size from the development of its nuclei into cells, 

 appears to undergo no further change ; but in each of the 

 Contained cells, which vary much in number, one spermato- 

 zoon is developed on the inner wall, in the form of a spiral 



