Fig. 172.—The Bat. (× ⅓.)
The voice of the bat is a shrill squeak, of so high a pitch that many people cannot hear it at all. The animal is probably quite blind, but it has keen powers of scent and hearing, and in avoiding obstacles seems to be greatly aided by patches of specially sensitive skin on the face, and by delicate whiskers. During the day it lurks in dark corners of barns, church-towers, hollow trees, etc., hanging head downward by the hooked claws of its hind feet.
On close examination the body of the bat is seen to be covered with soft fur, a character which at once proclaims the animal to be not a bird—as it has been incorrectly considered—but a mammal. The fur is often of a bright chestnut colour. The ears are large and practically devoid of hair, and are so thin as to be almost transparent. The wings are thin folds of skin, which are attached in front to the long arms, are supported by the greatly elongated fingers, and reach to the hind limbs. Another membrane passes between the hind limbs, and in common species is also supported by the tail. The thumb is free, and bears a claw which is of some assistance in climbing. The hind limbs are small.
The structure of the bat is obviously but little adapted to walking, and the animal moves about very awkwardly when on the ground, although it can rise on the wing again without much difficulty.
The bat is rarely to be seen abroad after the middle of November, for as the cold weather approaches and insects become scarce, it suspends itself by its hind claws in some dark and sheltered corner, and goes to sleep for the winter, reappearing in early spring.
50. HOOFED MAMMALS.
1. The external characters of the sheep.—(a) Wool.—How does the covering of a sheep’s body differ from the fur of a cat or rabbit, and from the hair of the dog? Examine a lock of “raw” wool; is it at all greasy? Dip it in water; is it much wetted? Are the fibres easily entangled together? Why is woollen clothing so warm?
(b) Teeth.—Obtain a sheep’s head from the butcher, and examine the teeth. Notice the absence of incisors and canines in the upper jaw, and of canines in the lower jaw. Observe the thickened pad on the surface of the upper jaw, against which the lower incisors bite. Are the cheek teeth flat, or sharp-edged like the cheek teeth of carnivores? Watch a sheep feeding, and notice how it bites the grass. How is the lower jaw moved during the chewing of the cud?
(c) Horns.—Which sheep have the largest horns, the males (rams) or the females (ewes)? If you can find a cast horn notice whether it is hollow or solid. What is the use of horns?