REP ROD UCTION. 



^Z 



BOOK II. 



OBSTETRICAL PHYSIOLOGY. 



REPRODUCTION. 



Having described the situation, structure, and peculiarities of the ex- 

 ternal and internal organs of the female domesticated animals, we have 

 now to inquire into their functions. These functions have for their end 

 the conception, development, and preservation of the young animal for a 

 certain period, until it can maintain a more or less independent existence, 

 when some of them are brought into play in order to place it in direct 

 relation with the external world in the act of parturition, while others 

 cease. But in order that generation should take place in the higher 

 classes of animals, it is necessary that the two sexes be placed in favor- 

 able relations with each other. This preliminary condition is indispen- 

 / sable, as the essential of reproduction is the contact with, and action of 

 the male fecundating fluid on, the ovum of the female. Nature has 

 ordained that this creative act should be accomplished by engendering 

 in these animals an instinctive, irresistible desire at a certain stage of 

 existence ; which desire, continuing only for a brief period, is renewed 

 after particular intervals, until the faculty of reproduction ceases. 



The advent of the power of reproduction in the male and female sex of 

 animals is very unequally distributed among the various species, and is 

 generally in proportion to the duration of their existence : the creatures 

 which are short-lived being capable of bringing forth young at an earlier 

 period of life than those which enjoy a longer term. 



The Elephant only brings forth one at birth, and this occurs but once 

 in three or four years ; while the descendants of the Rabbit in the same 

 space of time may be reckoned at more than a million. This great dis- 

 parity has nothing of chance or accident in it, but is in admirable har- 

 mony with the designs of Nature. The individuals of every species 

 produce, as has been justly remarked by Verheyen, a total number of 

 germs which amply covers the losses caused by death ; and the premature 

 destruction of many of these germs is likewise a providential safeguard 

 against their too numerous multiplication. 



Two factors regulate fecundity ; these comprise the nutritive excess 

 which the maintenance of the individual renders disposable, and the sum 

 total of the materials necessary for the embryonic evolution ; but the 

 divergences of these two factors are as extensive as those of fecundity 

 itself. 



If we take the weight of the foetus at birth as the equivalent to the 

 nutritive matter that the parent has endowed it with, and multiply this 

 weight by the number of young annually produced, we shall obtain the 

 total amount of the materials which have been derived from the maternal 

 organism. Then weighing the mother, and comparing her weight with 

 that of the foetus, we shall arrive at the disposable nutritive excess ; and 

 from this, according to Leuckart, be able to calculate the fertility of a 



