THE GERM CELLS 



II 



Perforatorium 



Head* 



Neck 



Connect- 

 ing piece 

 of tail 



Annuity 



Chief piece 

 of tail 



Ant. centrosomal body 

 Post, centrosomal body 



-Spiral filament 



Sheath of axial 



filament 

 Mitochondrial sheath 



the ovary (Fig. 5) and at these points the ovarian wall has become very 

 thin. At ovulation, that is, the bursting of the Graafian follicle and the 

 discharge of the ovum, but one ovum is usually liberated. Several ova, 

 however, may be produced in a single 

 follicle in rare cases. Such multiple 

 follicles have been observed in human 

 ovaries and are of frequent occurrence 

 in the monkey (Fig. 6). 



The observations of various older 

 workers (Leopold, Ravano and others) 

 led Mall (1910) to conclude that they 

 had ' ' shown conclusively that ovulation 

 and menstruation are usually syn- 

 chronous." Since then, Meyer, Ruge, 

 Shroder, Fraenkel, and Halban, utilizing 

 better standardized corpora lutea as 

 criteria, have presented evidence ac- 

 cepted by Grosser (1914) and Mall 

 (1918) as proof that ovulation occurs 

 most often between the fourth and 

 fourteenth day after the menstrual 

 onset. A survey of all the clinical data 

 indicates that any such relation is at 

 best very loose and that many ova are . 

 liberated without definite reference to 

 the menstrual cycle. -. Moreover, in 

 young girls ovulation may precede the . 

 inception of menstruation and it may 

 occur in women during pregnancy or 

 after the menopause. 



The Spermatozoon. The male cell, 

 or spermatozoon, of man is a. minute 

 cell 0.055 mm - long, specialized for. 

 active movement. Because of their 

 motility, spermatozoa when first dis- 

 covered were regarded as parasites 

 living in the seminal fluid. The sperm 

 cell is composed of a flattened head, short 

 neck, and thread-like tail (Figs, i and 7). 



The head is about 0.005 mm - m length. It appears oval in surface 

 view, pear-shaped in profile. When stained, the anterior two-thirds of 

 the head may be seen to form a cap, and the sharp border of this cap is the 



.Axial filament 



.Sheath 



End piece 

 of tail ' 



FIG. 7 . Diagram of a human 

 spermatozoon, ' surface view (Meves, 

 Bonnet). 



