42 PRINCIPLES OF PHYSIOLOGY 



or egg, derived from a female, and a sper- 

 matozoon, derived from a male parent. The 

 ovum is a small spherical vesicle about 1 /1 00 

 of an inch in diameter. Imbedded in its 

 protoplasm there is a large spherical nucleus, 

 termed the germinal vesicle, and, in the nucleus, 

 there is a still smaller body, the germinal 

 spot. Both the cell protoplasm and the 

 nucleus show a network of fine fibres, and in 

 the nucleus of the human ovum there are 

 chromosomes. The ovum is formed in a 

 special organ, the ovary, and at certain 

 periods the ovum is extruded into the Fallo- 

 pian Tube, a duct which leads to the uterine 

 cavity. 



The male element, the spermatozoon, is a 

 minute body consisting of a head and a long 

 vibratile tail. The total length is about 1 /500 

 of an inch, while the head, which is the im- 

 portant part, is about 1/10 of the length. 

 The head represents the nucleus of a cell in 

 which the spermatozoon has been developed, 

 and it contains the all-important chromatm 

 The spermatozoa are formed in enormous num- 

 bers in the cells of a special organ, the testis. 



