262 
NATURAL HISTORY, \ 
wing is expanded, this border shows two points besides that at the apex of the wing, and three more or 
less rounded notches, the last of which is between the tip of the fourth finger and the attachment ot 
the membrane to the hinder limb. 
In most Bats the membrane does not stop short at the legs, but encloses them after the same 
fashion as the arms, leaving only the foot and sometimes a part of the shank free. The portion of 
membrane that passes within the legs, sometimes filling up the whole space between them and 
enclosing the whole or a part of the tail, sometimes forming only a narrow border to these limbs is 
called the interfemoral or intererurul membrane, and the characters furnished by it and its relations to 
other parts are of great importance in the classification of Bats. 
The rest of the structure of these animals may be dismissed in a few words. The skull, and all 
the other parts of the skeleton, are generally light and delicate in their construction, as might be 
expected in animals destined to support themselves in the air ; but there is no trace of those pneumatic 
cavities which, in birds, enable the air to penetrate all parts of the skeleton. The jaws are well 
armed with teeth, which differ in their character in accordance with the food consumed by the animals. 
The ribs are well developed, and enclose a large chest cavity. The pelvis (p) is long, slender, and 
somewhat bird-like in some respects ; the legs are short, generally slender, and articulated in such a 
manner that when used in walking the knees are directed backwards, like our elbows ; the fibula 
(the second bone in the shank) is usually imperfectly developed, in the same way as the ulna in the 
fore-arm ] and the foot consists of five distinct toes, armed with small but sharp claws. V- which the 
animals suspend themselves from the surface of rocks, walls, and other objects, in the dark retreats to 
which they retire for their repose. From the heel-bone (calcaneum) in most Bats there springs a 
cartilaginous or bony rod or spur, which is regarded by some zoologists as forming part of the bone 
itself. This spur, which is often of considerable length, runs along the margin of the interfemoral 
membrane, which it no doubt helps materially to stretch. When long, and more or less curved, it often 
causes a projection of the side of the interfemoral membrane, as shown in the figure of the Marsh 
Bat (p. 259). The tail is very variable in length. 
In repose, or rather when not dying, the wings of the Bat are folded up by a reversal of the 
process by which they were extended for flight ; the long fingers are drawn together, and up towards 
the fore-arm, and the membrane forms leathery folds at the sides of the body. This is also their position 
when the animal is walking or running on the ground (see the engraving on the next page), which it 
does in a somewhat awkward fashion, by the action of its hind feet and the claws of its thumbs. 
When seen thus engaged there can be little doubt as to the quadruped nature of the Bat. Our little 
European species have a Mouse-like appearance, which fully justifies their old popular name. 
The teats are usually situated on the breast ) but sometimes they are placed quite on the sides, 
immediately beneath what we must call the armpits. They are two in number. In addition to these 
chest or pectoral teats, some species have been described as possessing a second pair of such organs 
situated on the groin, but recent investigations prove clearly that these are merely nipple-like warts. 
The organs of the senses are well developed. The ears are almost always of considerable size, 
sometimes very large and membranous, and in most cases there is in front of the cavity a sort of lobe 
of variable form, called the earlet, or tragus, representing the little rounded lobe which, in the human 
ear, projects from behind the cheek over the opening (see the woodcut of the Head of the Long-eared 
Bat). The nostrils are either simple slits or apertures at the end of the muzzle, or surrounded by 
leaf-like organs, often of the most extraordinary forms (see the Head of the Spectacled Vampire, 
p. 204, and other illustrations later on), in fact, this tendency of the skin in Bats to run out into 
membranous expansions is one of their most remarkable characteristics, and, from their mode of 
life, this great development of the skin system would seem to be almost essential to their existence. 
The old proverbial expression, “ As blind as a Bat,” is certainly not founded on a due appreciation 
of facts, for Bats are by no means blind ; on the contrary, they are furnished with very efficient eyes, 
although, in most cases, these are little bead-like organs, 'very unlike the eyes usually seen iu animals 
whose activity is nocturnal or crepuscular. But it would appear that the office of the eyes in guiding 
these animals is, at all events, supplemented by some other means. Towards the end of the last 
century, the Abbe Spallanzani made some exceedingly interesting, although certainly cruel experiments 
cn various species of Bats. He blinded these animals, Sometimes by burning the eyes with a red-het 
