Bat, a mammiferous quadruped, whose different genera constitute the order cheiroptera. Its general form is disposed for flight; an expansion of the skin is stretched between the four limbs and the greatly elongated fingers of the anterior extremities; this flying membrane is naked, or nearly so, on both sides; the breast has mammae; the clavicles are very strong; the forearm is incapable of rotation in consequence of the union of the bones. The bats consist of two very distinct groups, characterized mainly by the structure of the teeth. The first, containing the genera pteropvs and cephalotes, is frugivorous, has the molar teeth with flattish crowns, obliquely truncated and longitudinally grooved, 3 joints in the fingers, generally provided with a nail on the second finger, and the tail wanting or rudimentary. The second group, containing the genera vos-pertilio, phyllostoma, nycteris, etc, has the molars with sharp points like the true insecti-vora, showing at once the different nature of their food. The skeleton of the bats combines a great degree of lightness with peculiarities in the anterior extremities suitable for purposes of flight.
The head is the longest in the frugivorous group; in all, the portion of the temporal bone containing the organ of hearing is much developed; they all have canine and incisor teeth, the latter varying in number from 2 to 4 in the upper, and from 2 to 6 in the lower jaw; the molars also vary from 3 to 6 in each jaw. The vertebrae of the neck are very broad; those of the back and loins are simple and almost without spinous processes, and much compressed at the side; the sacrum is very long and narrow; the tail, when present, is short, and of use to support the interfemoral membrane and direct the flight. The number of vertebrae in pteropus is probably less than in any other mammal, being only 24. The ribs are remarkably long, as is the breast bone; the upper part of the latter is greatly expanded laterally, to give a firm support to the very strong collar bones; the front of the bone has also a crest, like the keel of the bird's sternum, and for a similar purpose, viz., the origin of the powerful muscles of flight.
As the collar bone, so the shoulder blade is highly developed, especially in the active insectivorous bats; the arm bone is very long and slender; the forearm consists of the usual two bones, but the ulna is quite rudimentary, and is united to the radius; the latter is very long and robust, and cannot be rotated, an admirable provision for an animal whose progression requires a constant resistance to the air. But the most remarkable modification of the anterior extremity is in the hand; the bones of all the fingers, except the thumb, are extremely elongated, for the attachment of the flying membrane; the thumb is comparatively short, and provided with a hooked nail, by which the animal can climb or suspend itself. The thigh bone is of moderate size, and so turned that the front surface is directed nearly backward; the fibula is quite small and slender, and has the remarkable condition of deficiency in its upper portion, the usual state of things being the reverse. The foot is not developed like the hand, the only peculiarity being a long-pointed bony process arising from the heel, and enclosed in the membrane between the legs; the toes are 5 in number, nearly equal, and furnished with hooked nails, by which they suspend themselves when at rest, with the head downward.
The seeming deformity and ugliness of the bats led the ancients to consider them as impure animals; even ancient naturalists display the grossest ignorance concerning them. Aristotle, Pliny, and others, considered them as birds; these opinions were copied during the middle ages, and are even now entertained by many persons. The faculty of flight depends on an entirely different organization in the bird and in the bat. The principal part of the bat's flying membrane is stretched between the enormously elongated fingers, and from them reflected to the posterior extremities; but in the bird, the parts which correspond to fingers are so rudimentary that the hand can hardly be said to exist; the wings extend beyond it, bearing the quills, the principal part, which belong to the epidermic system; the wings in the two cases are in no respects homologous. The bat, so active in the air, is very awkward on the ground. When the animal attempts to walk, the wings are shut and become fore feet; the hook of one thumb is fixed to some object, and by it the body is pulled forward and to one side, the next step being by a similar movement by means of the hook of the other thumb.
By this diagonal tumbling, the bats progress on a level surface; the length of the wings prevents them from rising from such a situation, and it is only when they gain some trifling elevation that they can commence their flight. In the air they are perfectly free, and when desirous of rest they seek some dark retreat, from the top of which they can hang, head downward, suspended by their hind claws; in case of danger, they have only to loose their hold, when their wings are at once spread. The diminutive size of the eyes is well known, and familiarly expressed in the very common saying, "as blind as a bat." The insectivorous group, whose ears are largely developed, have | very small eyes, placed almost within the auri-cle and concealed by the hair; but in the fruit-eating genera the eye is of the usual size, as is also the ear. The diminutive eye is compensated for by the great development of the organ of hearing; the external ear is enormously large, in the pleiotus auritus nearly as long as the body; there is a proportionate increase in the extent of the internal ear.
The organ of smell in many insectivorous bats, as the rhinolophidce, is exceedingly acute; it is provided with folds of the integument, of great size and the most grotesque forms, rendering their physiognomy like that which would be produced by a nose turned inside out and complicated by a hare-lip. These appendages are found in the groups whose habits lead them into the darkest caverns, where there is not even a ray of light, and are intended, by increasing the delicacy of the sense of smell, to act as substitutes for eyes in situations where vision is impossible. Bats have such an extraordinary exaltation of the sense of touch, that Spallanzani was led into the belief that they had a sixth sense; his experiments showed that they could fly with perfect accuracy in the dark, avoiding every obstacle, even after the eyes were put out and the ears and nose completely stopped up. But Cuvier discovered that this exquisite sense of touch resides in the flying membrane. This membrane arises from the skin of the flanks, and consists of an abdominal and a dorsal leaflet, united into an exceedingly thin and delicate network; it includes not only the arms and hands, but the hinder extremities, being prolonged more or less, according to the genera, between the legs, and spread the length of the tail, forming a sensitive surface entirely disproportionate to the size of the body; to increase its sensitiveness, it is entirely or nearly destitute of hair.
The bat, therefore, is made acquainted with the distance of bodies by the different modifications impressed upon this membrane by the impulse of the air. The only peculiarity in the nervous system is the large size of the spinal cord in the lower cervical and dorsal region, from which arise the nerves of sensation distributed to the wings. In the nycteris, an African genus, the skin adheres to the body only at certain points, and by a loose cellular membrane, and is capable of being inflated with air by a communication with the large cheek pouches; this inflation may be carried to such an extent that the animal resembles a balloon with head, wings, and feet. The mouth of the bat is uncommonly large, affording great facilities for the capture of insects on the wing. In the genus vampirus or phyllostoma, peculiar to America, the tongue is provided at its extremity with a circular row of wart-like elevations, forming a complete suctorial disk; by means of this these animals are enabled to suck the juice of fruits and the blood of animals.
By mistake this faculty has been attributed to some of the large species of the pteropus of Asia, and hence have arisen the fearful stories of the fabulous vampire, which destroyed people at night by sucking their blood, fanning their victims into unconsciousness by the flapping of their wings. The vampire bat is a large South American species, of the genus vampirus, whose natural food is insects, but which, if pressed by hunger, will suck the blood of poultry, cattle, and even of man; the blood is obtained entirely by suction from the capillary vessels, and not through any wounds made by the teeth; the stories told by travellers are much exaggerated, as the animal is harmless and not at all feared by the natives. The insectivorous bats have the simple stomach and short intestines of the carnivora; while the frugivorous species have a complicated stomach and a long alimentary canal. - Bats are natives of all the temperate and tropical regions of the globe; those of North America belong chiefly to the vespertilionidae. The large East India species, the roussettes, of the genus pteropus, are extensively used as food. The fur of bats is generally exceedingly fine and soft.
Bats fly to a considerable height and with great rapidity; they are nocturnal in their habits, avoiding the light and noise of day; in the warm summer evenings they sally forth in search of prey, and themselves fall easy victims to the owls and birds of night and to any snare that may be set for them; they pass the winter, and indeed the greater part of the year, in a state of torpidity. The cheiroptera are intermediate between the quadrumana and the true insectivora. The galeopithecus, or cat-monkey, of the Indian archipelago, presents many characters of the cheiroptera, though belonging to the quadru-mana; the frugivorous genera approach the quadrumana in their teeth, while the insect-eaters resemble the true insectivora in their dentition; we find the monkey characters also in the free movements of the thumb, the deep divisions of the fingers, the pectoral situation of the breasts, the cheek pouches of many, and in the organs of generation and digestion. The bats differ from the quadrumana especially in the great development of the breast bone and in the impossibility of rotating the forearm. - North America has the following bats: Vesper-tilio Noveboracensis, V. pruinosus, V. subulatus, V. noctivagans, V. Carolinensis, V. monticola, V. Virginianus; molossus cynocephalus, M.fu-liginosus; plecotus Lecontii, P. Townsendi.
Common Bat (Vespertilio communis).
Long-eared Bat (Pleiotus auritus).
Vampire Bat (Vampirus spectrum).
Flying Fox or Roussette (Pteropus rubricollis).