274 GENERATION. 



trate in the form of tubes, the so-called ovarian tubes, and, at 

 the same time, delicate processes, formed of connective tissue 

 and blood-vessels, extend from the fibrous stroma underlying 

 the epithelium and enclose collections of cells. It is probable 

 that we have these two modes of formation of follicles ; one, 

 by the penetration of epithelial tubes from the surface, which 

 become constricted and divided off into closed cavities, and the 

 other, by the extension of fibrous processes from below, which 

 enclose little collections of cells. By both of these processes, 

 little cavities are formed, which contain a number of cells. 

 In each of these cavities, we observe a single, large, rounded 

 cell, with a large nucleus, this cell being a primordial ovum ; 

 and, in addition, we have, in the same cavity, other cells, 

 which are the cells of the Graafian follicle. The exact nature 

 of the processes we have just described has been studied in 

 the fowl, but it is probable that the same kind of develop- 

 ment occurs in mammalia and in the human female. 



From birth until just before the age of puberty, the corti- 

 cal substance of the ovary contains thousands of what are 

 termed primordial follicles enclosing the primordial ova ; and 

 it is probable that, after the ovaries are fully developed' at 

 birth, no additional ova or Graafian follicles make their ap- 

 pearance. The prevailing idea is, indeed, that the great ma- 

 jority of these never arrive at maturity, and that they undergo 

 atrophy at various stages of their development. According 

 to the table of measurements given by "Waldeyer, from whose 

 article most of the facts we have stated have been taken, the 

 primordial follicles of the human embryo, at the seventh 

 month, are from about -g-J-g- to -g-J-g- of an inch in diameter, 

 and the primordial ova, from 16 1 SO to 7^$^ of an inch. In 

 the adult, the smallest follicles measure from about -g--^ to -g-J-g- 

 of an inch, and the smallest ova, a little more than y^nnr ^ an 

 inch. 1 The primordial ova have the form of rounded cells, 

 each with a large, clear nucleus, and a nucleolus. Other 



1 WALDEYER, in STRICKER, Manual of Human and Comparative Histology, The 

 New Sydenham Society, London, 1872, vol. ii., p. 207. 



