INTRODUCTION- 
XXYli 
upon others, it has assisted the weakness of one by 
granting it fruitfulness ; and diminished the num- 
ber of the other by fecundity. 
In consequence of this provision, the larger 
creatures, which bring forth few at a time, seldom 
begin to degenerate till they have nearly acquired 
their full growth. On the contrary, those which 
bring many, reproduce before they have arrived 
to half their natural size. Thus the horse and 
the bull are nearly at their best before they begin to 
breed ; the bare and the rabbit scarce leave the teat 
before they become parents in turn. Almost all ani- 
mals likewise continue the time of their pregnancy 
in proportion to their size. The mare continues 
eleven months with foal, the cow nine, the wolf 
five, and the bitch nine weeks. In all, the inter- 
mediate litters are the most fruitful ; the first and 
the last generally producing the fewest in number 
and the wor^t of the kind. 
Whatever be the natural disposition of animals 
at other times, they all acquire new courage when 
they consider themselves as defending their young. 
No terrors can then drive them from the post of 
duty ; the mildest begin to exert their little force, 
and resist the most formidable enemv. Where 
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resistance is hopeless, they then incur every dan- 
ger, in order to rescue their young by flight, and 
retard their own expedition by providing for their 
little ones. When the female opossum, an animal 
of America, is pursued, she instantly takes her 
