The Vulva 45 



of the female and spermatozoa in the testicle of the male. 

 Up to this time, the reproductive organs are dormant in so 

 far as their specific functions are concerned. Puberty, or 

 sexual maturity, occurs at varying ages in different species, 

 breeds, and individuals, depending upon the food supply 

 and rapidity of growth. It occurs quite uniformly in both 

 sexes prior to the completion of growth. 



Reproduction is a complex physiologic process, accom- 

 panied by or associated with phenomena which bear an im- 

 portant relation to each other. In approximately the fol- 

 lowing order, there are observed the maturation of the 

 ovisac — or Graafian follicle — estrum, copulation, rupture of 

 the ovisac, fecundation, and possibly menstruation. The 

 chain of phenomena is finally completed by pregnancy, par- 

 turition, and the nutrition of the new-born. 



The ovaries consist at first of a mere thickening of the 

 peritoneum, due to an elaboration of its epithelial cells. The 

 external cell layer becomes columnar. The cells of the 

 deeper strata assume a more or less cuboidal form, to con- 

 stitute the germinal cells, and certain of their number be- 

 come distinctly larger than the others, to form the primitive 

 ova. The deeper epithelial layers are broken into irregular 

 columnar masses, or egg columns, through the growth 

 among them from below of blood vessels and connective 

 tissue. Prior to birth, in those young which are born in a 

 well developed state, and shortly after birth in the imma- 

 ture young like that of the rabbit, some of the primitive 

 ova become materially changed, to constitute permanent 

 ova. In the cell masses the permanent ova, developed from 

 the primitive ova, become much larger than the others, 

 while the nucleus, or germinal vesicle enlarges and its en- 

 veloping membrane becomes distinct. The contents of the 

 nucleus become massed at one point and form a distinct 

 reticulum, in which one or more nodal points enlarge to 

 constitute the nucleolus, or germinal spot. The neighbor- 

 ing germinal cells become arranged about the ovum in such 

 a manner as to enclose it completely in a follicle, which has 

 at first a single layer of cells. Later a second layer of cells 



