THE GERM CELLS 



II 



Perforatorium 



Head' 



Neck 



Connect- 

 ing piece ' 

 of tail 



Annulus ■ 



Chief piece 

 of tail ^ 



-Cap 



Ant. centrosomal body 

 Post, centrosomal body 



-Spiral filament 

 -Sheath of axial 



, Mitochondrial sheath 



ments, spermatozoa were, when first discovered, regarded as parasites living in 

 the seminal fluid. The sperm cell is composed of a flattened head, short neck, and 

 thread-like tail (Fig. 8). 



The head is about 0.005 mm. in length. 

 It appears oval in side 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 perforatorium by means of which 

 the spermatozoon penetrates the ovum. 

 The head contains the nuclear elements of 

 the sperm cell. The disc-shaped neck con- 

 tains the anterior centrosomal body. The 

 tail begins with the posterior centrosomal 

 body and is divided into a short connecting 

 piece, a chief piece or flagellum, which forms 

 about four-fifths of the length of the sperm 

 cell, and a short end piece, or terminal fila- 

 ment. The connecting piece is marked off 

 from the chief piece by the annulus. The 

 connecting piece is traversed by the axial 

 filament (filum principale), and is sur- 

 rounded (1) by the sheath common to it 

 and to the flagellum; (2) by a sheath con- 

 taining a spiral filament; and (3) by a 

 mitochondrial sheath. The chief piece is 

 composed of the axial filament surrounded 

 by a cytoplasmic sheath, while the end piece 

 comprises the naked continuation of the 

 axial filament. 



The spermatozoa are motile, being 

 propelled by the movements of the tail. 

 They swim always against a current at the rate of about 2.5 mm. a minute. This 

 is important, as the outwardly directed currents induced by the ciliary action of 

 the uterine tubes and uterus direct the spermatozoa by the shortest route to the 

 infundibulum. Keibel has found spermatozoa alive three days after the execution 

 of the criminal from whom they were obtained. They have been found motile 



-Axial filament 

 .Sheath 



End piece J 

 of tail I 



Fig. 8. — Diagram of a human spermat- 

 ozoon, highly magnified, in side view 

 (Meves, Bonnet). 



