THE DEVELOPMENT OP THE EMBRYO ITSELF. I33 



Semen itself, thougTi composed essentially of spermatozoa, 

 is mixed with the secretions of the vas deferens, of the seminal 

 vesicles, of Cowper's glands, and of the prostate. Chemically it 

 is neutral or alkaline in reaction, highly albuminous, and con- 

 tains nuclein, lecithin, cholesterin, fats, and salts. 



The movements of the male cell, owing to the action of the 

 tail (cilium), suffice of themselves to convey them to the ovi- 

 ducts ; but there is little doubt that during or after sexual con- 

 gress there is in the female, even in the human subject, at least 



Fig- 138 —Uterus and ovaries of the sow, semi-diagrammatic (after Dalton). 0, ovary: 

 H, Fallopian tube; h, horn of the uterus; S.Tjody of the uterus; v, vagina. 



in many cases, a retrograde peristalsis of the uterus and ovi- 

 ducts which would tend to overcome the results of the activity 

 of the ciliated cells lining the oviduct. It is known that the 

 male cell can survive in the female organs of generation for 

 several days, a fact not diiBcult to understand, from the method 

 of nutrition of the female cell (ovum) ; for we may suppose that 

 both elements are not a little alike, as they are both slightly 

 modified amoeboid organisms. 



Nervous Mechanism — Incidental reference has been made to 

 the directing influence of the nervous system over the events 

 of reproduction ; especially their subordination one to another 

 to bring about the general result. These may now be consid- 

 ered in greater detail. 



Most of the processes in which the nervous system takes 

 part are of the nature of reflexes, or the result of the automa- 

 ticity (independent action) of the nerve-centers, increased by 

 some afferent (ingoing) impressions along a nerve-path. It is 

 not always possible to estimate the exact share each factor 

 takes, which must be highly variable. Certain experiments 

 have assisted in making the matter clear. It has been found 



