

TESTICLE 



191 



epithelium 



albuginea 



on during all the later months of foetal life, but is completed by the time of birth 

 or shortly after. 



According to the important researches of Winiwarter, ' the germinal epithelium comprises two 

 layers of cells with nuclei of distinctive characters. In the superficial layer, the nuclei stain 

 deeply as a whole, but the nuclear network is very delicate, and the nuclear membrane is indis- 

 tinct ; in the deeper layer the nuclei are smaller, but the network is coarser, with distinct 

 karyosomes, and the nuclear membrane is an obvious feature. There is no true nucleolus in 

 either variety of nucleus. Winiwarter names them ' noyaux protobroques a and &.' In the epithelial 

 masses invading the stroma, cells with ' noyaux protobroques b ' are seen in active division, but 

 there is also a third variety of cell with a large clear nucleus and distinct nucleolus (noyau deuto- 

 broque). These cells no longer divide, and are the young oocytes. In the nuclear division pre- 

 ceding the appearance of these cells the prophase of the heterotypical division has been initiated 

 by the synapsis, in which the chromatin-loops fuse in pairs (see p. 17). The cells with ' noyaux 

 protobroques b ' become the follicular cells. As these gather round the oocytes they become 

 arranged in a continuous low columnar epithelium. The cells, however, multiply, and form, 

 soon, a many-layered investment to the oocyte. The liquor folliculi next gathers among the 

 cells, and separates a mass surrounding the ovum and attached to the wall of the follicle named 

 the discus proligerus (cumulus oophorus), 

 from the cells lining the follicle or stratum 

 granulosum. Outside this epithelial 

 layer the connective tissue becomes 

 condensed round the ovum into the 

 theca folliculi, which shows two layers, 

 an external (theca externa) more fibrous, 

 and an internal (theca interna) more 

 cellular. The cells in the theca interna 

 are rounded or polygonal elements of 

 some size, which exactly resemble the 

 interstitial cells scattered in the ovarian 

 stroma. These interstitial cells are 

 generally regarded as being derived from 

 the mesenchyme, but Miss Lane- Clay ton 2 

 has supplied evidence which seems to 

 show that they may be derived like the 

 follicular cells from the germinal epithe- 

 lium. The cells of the corpus luteum 3 

 are considered by some as arising from 

 the stratum granulosum, by others from 

 the cells of the theca interna. 



The tubules which have been ob- 

 served by various authors near the 

 hilum of the gland, and named the 

 rete tubules because they are regarded as 

 being homologous with the tubules of the 



rete testis, have been generally regarded as derivatives of Wolffian tubules, but according to the 

 results of Coert and Allen, referred to above, they arise like the primary genital cords from the 

 coelomic epithelium. 



The testicle is early distinguished from the ovary by the reduction that takes 

 place in the germinal epithelium, which becomes marked off from the parenchyma 

 of the gland by a layer of connective tissue, the future tunica albuginea. The 

 genital cords of the primitive gland become the seminal tubules. These, which 

 of course are at first solid, consist of smaller cells probably representing the cells 

 of the germinal epithelium, and larger rounded sex-cells. The tubules acquire 

 a lumen quite late in their history, and increasing in length become coiled (fig. 242). 

 The larger rounder cells multiply, and ultimately line the greater part of the wall of 



1 Archives de Biok>gie, 1900. 



- Journ. of Phys. xxxii. 1905, and Journ. of Obstet. and Gynec. xi. 1907. 



3 See ' Ovary ' in volume on Splanchnology. 



supporting _ J 

 cell. 



genital cell 



FIG. 242. SECTION OP ONE OF THE GENITAL CORDS 

 OF THE TESTICLE OF A HUMAN EMBRYO OF 

 3-5 CM. LONG. (Felix and Biihler.) 



