XXX V] TISSUES OF REPRODUCTION 277 



been taken from a young animal). The corpora lutea 

 vary greatly in size and appearance according to their 

 age ; at their maximal development they consist of 

 narrow radiating threads of stroma, between which are 

 a number of large polygonal cells ; if the corpus luteum 

 is younger there will be pigment (from effused blood) 

 in its centre; and at a still younger stage the larger 

 central part will contain blood, and the peripheral zone 

 consist of a fine network of branched cells with poly- 

 gonal cells in their meshes. (This is better seen in the 

 ovary of the rabbit.) 



2. Observe with a high power 



a. The peripheral parts of the stroma consist 

 chiefly of elongated spindle-shaped cells. 



b. The small Graafian follicles. Note in these 

 The ovum, large and spherical; within it lies a 



comparatively large spherical nucleus, the germinal 

 vesicle, in which may be seen a nucleolus, the germi- 

 nal spot. 



The membrana granulosa, a layer of flattened 

 epithelium cells . immediately surrounding the ovum. 



The thin membrana pr,opria enclosing the membrana 

 granulosa. 



In the smallest Graafian follicles the membrana 

 propria will not be seen, in the larger ones the cells 

 of the membrana granulosa become cubical or short 

 columnar and the ovum has a membrane (cp. c). 



c. The large Graafian follicles. Note in these 

 The stroma investment of the follicles, consisting 



chiefly of spindle-shaped cells, partly of fine fibrous 

 tissue ; inside this is the membrana propria. 



