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  Section: Anatomy of Vertebrate Animals » The Classification and Organization of the Mammalia
 
 
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The Cheiroptera

 
     
 

The Cheiroptera may be regarded as exceedingly-modified Insectivora, having their nearest ally in Galeopithecus.

They possess one or two pair of pectoral teats; and the fore-limbs are very long, some of the digits particularly being immensely elongated. There is a patagium, or expansion of the integument, uniting the fore-limbs with the body, and extended, as a membranous web, between the elongated fingers. Of these, the third, fourth and fifth, and very frequently the second, are devoid of nails. The pollex always has a clawlike nail. When the animal is resting upon the ground, the thigh is twisted upward and backward, in such a manner that its extensor face looks forward, and its flexor face backward. In consequence of this the knee looks upward and backward, and the toes are turned backward and slightly outward. Under the same circumstances, all the digits of the manus are flexed upon their metacarpal bones; and the folded-up wing rests against the side of the body, while the pollex, with its claw, is extended forward. In this position the animal shuffles along, with considerable rapidity; hauling itself forward by the claws on the polHces, and shoving itself along, by extending the hind-limbs.

The favorite attitude of a Bat, when at rest, however, is that of suspension by the claws of one or both legs, with the head downward and the patagium folded over it like a cloak, The most active movement of the Bat is effected by flight, the fore-limbs being extended, and the patagium, which they support, playing the part of the feathers of a bird's wing.

The cervical vertebrae are remarkably large in proportion to the others, but, as in the rest of the vertebral column, the spinous processes are very short. The ribs are long and curved, so as to include a relatively capacious chest. The manubrium of the sternum is very wide, and the middle of its under surface raised into a crest. In the lumbar region, the vertebral column is bent, so as to be concave forward and to describe almost the quarter of a circle. As a consequence, the axis of the sacrum is at right angles to that of the anterior thoracic vertebrae.

In the skull, the orbit is not divided by bone from the temporal fossa, and the premaxillae are relatively small, and sometimes altogether rudimentary.

The clavicles are remarkably long and strong, and the broad scapula has a strong spine. The ulnae are imperfect distally, the carpus being borne altogether by the radius. There is only a single bone in the proximal row of the carpus, the pisiform being absent. Those digits of the manus which are devoid of nails possess not more than two phalanges.

The pelvis is very narrow and elongated, and the pubic bones are widely separated at the symphysis, as in some Insectivora. The anterior caudal vertebrae and the ischia are frequently united. The axes of the acetabula are directed toward the dorsal side of the body as well as outward; whence, in part, arises the peculiar position of the thigh, which has already been described. The fibula is rudimentary, its upper part being represented only by ligament, and there is an elongated bone, or cartilage, attached to the inner side of the ankle-joint which lies in and supports the patagium, and is called the calcar. The distal moiety of the tarsus readily rotates upon the astragalus and calcaneum, permitting the sole to turn inward with much ease.

All Cheiroptera possess three kinds of teeth, incisors, canines, and molars; and the intestine is devoid of a caecum.

The heart is provided with two superior cavae, a right and left; and the smooth cerebral hemispheres leave the cerebellum completely exposed.

The testes are abdominal throughout life, or may descend into the perinaeum, but there is no true scrotum. The penis is pendent. There are vesiculce seminales. The form of the uterus varies, being sometimes rounded and sometimes two horned.

The Bats are ordinarily divided into the Frugivora and the Insectivora. a. The Frugivora live, as their name implies, exclusively upon fruits. With the single exception of Hypoderma, all the genera embraced in this group have a nail on the second digit of the manus, and the crowns of the molar teeth, which soon wear down, are, when entire, divided by a longitudinal furrow.

The incisors do not exceed 2.2/2.2.
The pyloric portion of the stomach is immensely elongated. The nose has no foliaceous appendages, and the welldeveloped pinna of the ear has the ordinary form, neither the tragus, nor any other part, being unusually developed.

These Bats are confined to the hotter parts of the Old World and of Australia, where, from their dog-like heads and reddish color, they are known as "Flying-Foxes" (Pteropus, Harpyia, etc.).

b. The division of the Insectivora contains Bats which, for the most part, live upon insects, though some delight in fruits, and others suck the blood of larger animals.

The second digit of the manus is devoid of a nail, and sometimes is without any bony phalanges.

The stomach is usually pyriform, with a moderate cardiac enlargement. The molar teeth almost always have such a pattern as is observed in the typical Insectivora, and do not exceed six, or fall below four, on each side above and below.

The incisors are ordinarily 2.2/2.2 or 2.2/3.3, but their number may be much reduced.

The integument of the nose is developed into an appendage which is sometimes very large and leaf-like, and the tragus of the large ears is often similarly modified. The tail is often long, and sometimes prehensile.

The genera Desmodus and Diphylla (of which the group Hematophilina has been formed) are the most completely blood-sucking of all the Bats in their habits. They have a pair of enormous, sharp-pointed, upper incisors, while the four lower incisors are small and pectinated. The canines are very large and sharp, and the molars, which are reduced to two above and three below, on each side, have their crowns converted into sharp longitudinally disposed ridges, like the; edges of scissors. In Desmodus, the very narrow oesophagus leads into a stomach which would be of extremely small dimensions, were it not that its cardiac end is dilated into a great sac, which is longer than the body, and lies, folded up on itself, within the cavity of the abdomen. Into this sac it would appear that the blood swallowed by the animal at first passes, to be thence slowly drawn along the intestine.

Mr. Darwin ("Voyage of the Beagle," Mammalia, p. 2.) thus speaks of the habits Desmodus D' Orbignyi;

"The Vampire Bat is often the cause of much trouble by biting the horses on their withers. The injury is generally not so much owing to the loss of blood as to the inflammation which the pressure of the saddle afterward produces. The whole circumstance has lately been doubted in England. I was therefore fortunate in being present when one was actually caught on a horse's back. We were bivouacking late one evening near Coquimbo, in Chili, when my servant, noticing that the horses were very restless, went to see what was the matter, and, fancying he could distinguish sometliing, suddenly put his hand on the beast's withers and secured the Vampire. In the morning the spot where the bite had been inflicted was easily distinguished, from being slightly swollen and bloody. The third day afterward we rode the horse without any ill effects."

 
     
 
 
     



     
 
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