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Text 20
I. Read the text and state what information it carries.
CHARACTERISTICS OF MAMMALS
Mammals are characterized by having hair. They have ruled the animal
world thousands of years ago. This place they have maintained because they
have the best developed brains of all animals. They are warm-blooded (the body
temperature remaining the same in winter and in summer), breathe by means of
lungs, give birth directly to young, and are provided with milk glands to suckle
their young. A muscular wall (diaphragm) subdivides the body cavity into two
parts. The anterior contains the four-chambered heart and the lunge; the
posterior contains the stomach, intestines, liver, kidneys, and reproductive
organs. At birth the young resemble the parents in having the same parts.
All the animals are able to live because they secure food which nourishes
their bodies, exercise the function of respiration, excrete waste, are adapted to
their environment, and reproduce their kind.
Most mammals have two pairs of limbs; the fore limbs may be variously
modified for different uses, as for running on hard ground in animals like the
horse, for tree-climbing and food-getting in the squirrel, for flying in the bats,
and for swimming in the seals. In all fore limbs of mammals, even those as
different as the leg of squirrel, the flipper of the whale and seal, and the wing of
the bat, the arrangement of the bones la the same.
The hind legs of mammals do not show so much variation as the forelegs,
but in some eases, as in the whale, the hind legs have almost disappeared
through disuse and there is no external evidence of them.
The skeleton of mammals is built on a similar pattern in all cases. Even
'apparently marked differences are found, on examination, to be only modifications
of similar parts. In the vertebral column there are several regions, such as neck, rib,
back hip, and tail. It happens that the number of the separate vertebrae in the neck
region is the same in the dog, horse, giraffe, be man, etc., but the neck region is not
of the same length. This is very conspicuous in the giraffe, but when one examinee
this ver long neck he will find only the regular seven neck vertebrae. Each of these
vertebrae in the neck of the giraffe is very large, and this adaptation helps him in
securing his food, which consists о the leaves of trees.
II. Remember the following words and word combinations, consult a dictionary
about the way they are pronounced:
brain мозг
breathe дышать
give birth to рождать
suckle кормить грудью; вскармливать
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