ON PARTURITION. 541 



Aristotle/ and already cited by me, which is, that all parts 

 are made for a certain function, and if the function ceases to be 

 required that they themselves disappear. The eye sees, 

 the ear hears, the brain perceives, the stomach digests, not 

 because such characters and structures (naturally) belong 

 to these organs ; but they are endowed with such characters 

 and structures to accomplish the functions appointed them by 

 nature. 



On grounds like these it would appear that the uterus holds 

 the first place among the organs destined for generation ; for 

 the testicles are made to produce semen, the semen is for the 

 purposes of intercourse, and coition itself, or the emission of 

 the semen, is instituted by nature that the uterus may be 

 fecundated and generation result. 



I have said before that an egg is, as it were, the fruit of 

 an animal, and a kind of external uterus. Now, on the other 

 hand, we may regard the uterus as an egg remaining within. 

 For as trees are gay with leaves, flowers, and fruit at stated 

 periods, and oviparous animals at one time conceive and produce 

 eggs, at another become effete, so that neither the "place" 

 or the part that contained them can be found, so have 

 viviparous animals their spring and autumn allotted them. 

 At the season of fecundation the genital organs, especially in 

 the female, undergo great changes, so much so that in birds, 

 the ovary, which at other times is scarcely visible, now becomes 

 turgid; and the belly of the fish, near about the time of spawn- 

 ing, far exceeds in bulk the rest of the body, owing to the 

 enormous number of ova and the quantity of semen contained 

 Avithin it. In very many viviparous animals the genital organs, 

 that is, the uterus and spermatic vessels, are not always found 

 presenting the same mode and course of action and structure ; 

 but as they are capable or not of conception, so changes take 

 place, and to such an extent that the organs can hardly be 

 recognized as the same. In nature, just as there is nothing 

 lacking, so is there nothing superfluous ; and thus it happens 

 that the organs of generation wither away and are lost when 

 there is no longer any use for them. 



At the period of coitus in the hare and mole, the testicles 



' De Gen. Anim. lib. i, cap. 5. 



