54 



OBSTETRIC A L PHYSIOL OG Y. 



species. Although this calculation is only approximate, it none the less 

 demonstrates, in principle, the relations between fecundity and the two 

 before-mentioned factors. This is shown in the following table, drawn up 

 by Leuckart, with reference to the domesticated animals. 



The nutritive reserve of the Horse, compared with that of the other 

 animals, is here seen to be very limited ; while, on the contrary, the Fowl 

 yields in reproductive material a sum equivalent to five times the weight 

 of its own body. When a balance is struck between the profits and losses 

 in the animal economy, it is found that the great difference existing has 

 its own reasonable explanation. The function which makes the greatest 

 demand upon the nutritive capital, is doubtless that with which the mus- 

 cles are charged ; and their maintenance in power exacts the heaviest 

 compensation ; as they consume material in proportion to the weight of 

 the body, and the energy, extent, and frequency of the movements. In 

 proportion as the height increases, the cubical weight augments at the 

 expense of the motive power ; while the latter, equal to the square of the 

 transverse section of the muscles, follows an arithmetical, and not a geo- 

 metrical, progression. 



The nutritive maintenance, then, demands in an absolute manner an 

 expenditure much more considerable in the larger than the smaller an- 

 imals ; so that the latter are more fruitful than the former, and their 

 economy renders them more apt to hold in reserve a much more consid- 

 erable nutritive capital. 



A rich and abundant aliment, given regularly, increases reproductive- 

 ness ; as is evidenced in the case of our domesticated animals, if com- 

 pared with the wild creatures of the same species ; and the fecundity in- 

 creases or declines as their food is plentiful and good, or scarce and bad. 

 But this influence of alimentation on fecundity, and the faculty of living 

 beings to maintain a nutritive reserve, has its limit ; for the intestinal 

 absorption goes on in direct proportion to the superficies of the mucous 

 membrane lining it, and this is definite. 



The sum of materials necessary for embryonic evolution is also 

 founded on the nutritive reserve. In proportion as the organization is 

 simplified and the various apparatus decrease in number, so does the 

 maturity of the embryo gain in precocity, and the nutritive matter serve 

 for a larger number of germs. Thus, as has been aptly said, what would 

 be required to maintain the single foetus of a large mammal, whose or- 



