540 



THE CELL AND MAMMALIAN HISTOLOGY 



that movement is impossible. Sutures are usually completely 

 obliterated in older animals by complete fusion of the bones. 



GONADS 



The ovary (Fig. 422) consists of a mass of fibrous tissue with 

 some smooth muscle covered by the germinal ' epithelium '. 



Tunica aibugmea. Germinal. 



epithelium. 



Group of r ^--^^-^^-^ "^Advanced graafian 



small foUides./ Stroma. follicle. 



Fig. 422. — Part of a section of an ovary of a rabbit X c. 30. 



Seminiferous tubule . 



Space produced 

 by shrinkage. 



fnterstitial tissue. 



Fig. 423. — Diagrammatic transverse section of a part of a testis of a rat X c. 25. 



This sinks in at places and at each it becomes pinched off to form 

 a mass of cells, one of which becomes an ovum. The others form a 

 hollow Graafian follicle, consisting of a wall, the membrana 

 granulosa, with at one place an inner swelling, the discus proligerus, 

 which surrounds the ovum. Round each follicle the connective 



