REPRODUCTION. 



689 



though they are most abundant toward its peripheral portions. It is esti- 

 mated that each human ovary contains from 20,000 to 40,000 follicles. The 

 follicles vary considerably in size; while many are visible to the unaided eye, 

 others require for their detection high powers of the microscope. Although 

 the follicles are present in the ovary at the time of birth, it is not until the 

 period of puberty that they assume functional activity. 



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

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

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

 cells, the membrane, granulosa. At the lower portion of this membrane there 

 is an accumulation of cells, 

 the proligerous disc (Fig. 345). 

 The cavity of the follicle con- 

 tains a slightly yellowish, 

 alkaline, albuminous fluid, a 

 transudate in all probability 

 from the blood-vessels. The 

 Graafian follicle is of especial 

 interest, for it is in this struc- 

 ture, and more especially in 

 the proligerous disc, that the 

 true germ-cell or ovum is 

 developed. 



The ovum is a spheric 

 body measuring about 0.3 

 mm. in diameter. It consists 

 of a mass of living, proto- 

 plasmic material, cytoplasm, 

 a nucleus or germinal vesicle, 

 and a nucleolus or germinal 

 spot. The cytoplasm presents 

 toward its central portion a 

 quantity of granular material, 

 partly fatty in character, the 

 deutoplasm or vitellus. The 

 peripheral portion of the cyto- 

 plasm is surrounded by a 



Clear thick membrane, the granulosa. e. Discus proligerus. /. Zona pellucida. 



g. Vitellus. h. Germinal vesicle, i. Germinal spot. 

 k. Cavity of liquor folliculi. (After Piersol.) 



FIG. 345. SECTION OF CORTEX OF CAT'S OVARY, 

 EXHIBITING LARGE GRAAFIAN FOLLICLES, a. Per- 

 ipheral zone of condensed stroma. b. Groups of im- 

 mature follicles, c. Theca of follicle, d. Membrana 



icida. 

 spot. 



zona pellucida, external to 

 which is a layer of radially 

 placed columnar epithelium, the corona radiata (Fig. 346). 



The nucleus 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 

 materials, and hence are known as chromatin, in the meshes of which lies a 

 material that stains less deeply and known as achromatin. 



The Fallopian Tubes. The Fallopian tubes are about 12 centimeters 

 in length and extend from the upper angles of the uterus to the ovaries. 

 Each tube is somewhat trumpet-shaped, the narrow portion being close to 



44 



