56 



OBSTETRICAL PHYSIOLOGY. 



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 muscles are charged, and their maintenance in power 

 exacts the heaviest compensation ; as they consume material in pi-opor- 

 tion 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 geometrical, progression. 



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

 expenditure much more considerable in the larger than the smaller 

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

 economy renders them more apt to hold in reserve a much greater 

 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 their fecundity 

 increases 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 organisation 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 

 organisation is complete at its birth, would suffice for the evolution of 

 many million of frogs. Besides, the parent having once evacuated the 

 product of her fecundation, has done with it — the tadpoles issuing from 

 the ova find their nourishment in the outer world; but the young 

 mammal derives its sustenance from the mammte of the mother, at 

 whose expense it continues, for a more or less protracted period, to live 

 as a parasite (as it really was in utero). With the higher animals, 



