398 ZOOLOGY. 
them. In the case of mammals living in pairs, as in Carnivora, the male 
usually takes his part in this safeguard. 
All mammals have a voice, which is very diversified, although not so 
much so as in birds. 
Among all classes of animals, that of mammals is undoubtedly the one 
which is the most profitable to man, especially the domesticated kinds. 
Their flesh serves as food, as also the milk. The skin, fur, hair, and wool 
have a thousand applications. Several animal substances are used as 
medicines, and others as perfumery, still others as fuel (as for instance, the 
excrements of the camel); teeth, bones, hairs, horns, antlers, entrails, skin, 
muscle, tendons, as also blood and fat, are worked up and made use of in 
various ways. Finally, many serve us as guides in hunting, as beasts of 
burden, or as vigilant guards of life and property. 
The class of mammalia exhibits the greatest variety of habits among its 
members. Created to inhabit chiefly dry land, it is met with in every 
situation and locality, from the edge of the water to the top of the moun- 
tains, from the surface of the ground and under it to the top of the trees, in 
forests, open land, dry and wet, everywhere, exposed to the bright sun of 
the equator and to the frozen regions of the poles. Some frequent watery 
places, the banks of rivers, lakes, the beaches and sea shores Still others, 
entirely pelagic, are never seen near the land, except when thrown ashore 
by storms or other accidental causes. Again, in relation with all these 
circumstances of habitation, there are habits and instincts by which each 
species secures its food, escapes the dangers of its enemies or attacks a 
defenceless prey, and provides for the perpetuity of its race. 
CLASSIFICATION. 
Of the numerous systems of classification of mammals hitherto proposed, 
no one appears satisfactory to us. From the time that whales and dolphins 
(Cetacea) were acknowledged to be mammals, they have been considered 
as the lowest of all, on account of their inhabiting the water, and the 
analogy of their form with that of fishes. In all systems of classification 
they are placed lowest. This position is assigned them in the Systema 
Nature of the great Linneus. In Cuvier’s Animal Kingdom, the Cetacea, 
as usual, are placed at the bottom of the class, the Ruminantia come next, 
then Pachydermata, then Hdentata, then Rodentia, then Marsupialia, then 
Carnivora, Insectivora, Cheiroptera, and, finally, Quadrumana. Others 
make Pachydermata follow the Cetacea and precede Ruminantia, which 
appears to us much more correct. But the place assigned to Edentata and 
Marsupialia, we believe, is arbitrary, for, as they stand, they rather obscure 
than enlighten the affinities of the neighboring orders. 
During the last ten years, a modification has been introduced into our 
systems, which consists of dividing the class into two sub-classes, namely, 
the Monodelphes, including the generality of mammals whose young, when 
just born, require no other care from their parent except to suckle them ; 
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