REPRODUCTION 



727 



'hile many are .visible to the unaided eye, others require for their detection 

 igh powers of the microscope. Although the follicles are present in the 



'ary at the time of birth, it is not until the period of puberty that they as- 



.me functional activity. 



From this time on to the catamenial period there is a constant growth 

 .nd development of these follicles. Each follicle consists of an external 

 .ivestment of fibrous tissue and blood-vessels, and an internal investment of 

 :ells, the membrana granulosa. At the lower portion of this membrane there 

 an accumulation of cells, the proligerous .disc (Fig. 326). The cavity of 

 he follicle contains a slightly yellowish, alkaline, albuminous fluid, a 

 ransudate in all probability from the blood-vessels. The Graafian follicle 

 s of especial interest, for it is in this structure, and more especially in the 

 .roligerous disc, that the true germ-cell or ovum is developed. 



F IG . 327. OVUM OF A Cow. i. Zona 

 pellucida. 2. Cytoplasm, vitellus. 3. Nu- 

 cleus, germinal vesicle. 4- Nucleolus, germ- 

 inal spot. 5. Corona radiata. The radial 

 striation of the zona pellucida cannot be 

 seen. (Stohr.) 



FIG. 328. FRONTAL SEC- 

 TION OF THE UTERUS, i. Cav- 

 ity of the body. 2, 3. Lateral 

 walls. 4,4- Cornua. 5. Os 

 internum. 6. Cavity of the 

 cervix. 7. Arbor vitae of the 

 cervix. 8. Os externum. 9. 

 Vagina. (Sappey.) 



The ovum is a spheric body measuring about 0.3 mm in diameter. It 

 consists of a mass of living, protoplasmic material, cytoplasm a nucleus or 

 iSIrt*, and a nucleolus or gennmal spot The cytoplasm present 

 foward its central portion a quantity of granular material, partly fatty in 

 character, the deutoplasm or vitellus. The penpheral portion of the cyto- 

 Dlasm is surrounded by a clear thick membrane, the zona pelluctda, external 

 which is aTayer of radially placed columnar epithelium, the corona radtoto 



Thueus consists of a nuclear membrane enclosing contents .The 

 latter consist of an amorphous material in which is embedded a network, 

 some of the threads of which have a strong affinity for certain staining 

 mSerials and hence are known as chroma**, in the meshes of which lies a 

 material that stains less deeply and known as achromatin. 



