444 OF GENERATION AND DEVELOPMENT. 



satisfactorily distinguished within it. The movements are principally 

 excited by the undulations of the tail, which give a propulsive action 

 to the body. They may continue for many hours after the emission of 

 the fluid ; and they are not checked by its admixture with other secre- 

 tions, such as the urine, and the prostatic fluid. When the seminal 

 fluid remains in contact with a living surface (as when deposited in the 

 generative organs of the female), the Spermatozoa may retain their 

 vitality for some days ; and an instance has already been referred to 

 ( 240), in which the later stages of the development of the Sperma- 

 tozoa actually take place in this situation, the seminal fluid emitted 

 by the male (among many Crustacea) not containing any Spermatozoa 

 completely formed, but numerous spermatic cells, which undergo the 

 remainder of their development, and then rupture and set free their 

 contents, within the oviducts of the female. 



788. The power of procreation does not exist in the Human Male 

 (except in rare cases) until the age of from 14 to 16 years ; at which 

 epoch, the sexual organs undergo a much-increased development ; and 

 the instinctive desire, which leads to the use of them, is awakened in 

 the mind. From that time to an advanced age, the procreative power 

 remains, in the healthy state of the system ; unless it be exhausted by 

 excessive use of it, or by too energetic a direction of the mental or 

 corporeal powers to some other object. The formation of Seminal fluid 

 being, like the proper acts of Secretion, very much influenced by con- 

 ditions of the Nervous System, is increased by the continual direction 

 of the mind towards objects which arouse the sexual propensity ; and 

 thus, if sexual intercourse be very frequent, a much larger quantity of 

 the fluid will be produced, than if it is more rarely emitted, although 

 the amount discharged on each occasion will be less. The formation 

 of this product is evidently a great tax upon the corporeal powers ; and 

 it is a well-known fact, that the highest degree of bodily and mental 

 vigour is inconsistent with more than a very moderate indulgence in 

 sexual intercourse ; whilst nothing is more certain to reduce the powers, 

 both of body and mind, than excess in this respect. 



789. It may be stated as a general law, prevailing equally in the 

 Vegetable and Animal kingdoms, that the development of the indi- 

 vidual, and the reproduction of the species, stand in an inverse ratio 

 to each other. We have seen that, in many organized beings, the 

 death of the parent is necessary to the production of a new generation ; 

 and even in numerous species of Insects it follows very speedily upon 

 the sexual intercourse. It is a curious fact, that Insects which usually 

 die, the male almost immediately after the act of copulation, and the 

 female very soon after the deposition of the eggs, may be kept alive 

 for many weeks or even months, by simply preventing the copulation. 

 And there can be no doubt that, in the Human race, early death is by 

 no means an unfrequent result of the excessive or premature employ- 

 ment of the genital organs ; and where this does not produce an 

 immediately-fatal result, it lays the foundation of future debility, that 

 contributes to produce any forms of disease to which there may be a 

 constitutional predisposition, especially those of a Scrofulous nature. 



790. The emission of the Spermatic fluid is an act of a purely reflex 



