Page:Encyclopædia Britannica, Ninth Edition, v. 15.djvu/429

Rh CHTROPTERA.] MAMMALIA 407 which articulates with but a small part of the humerus, is ankylosed with the radius ; immediately beyond the joint it is reduced to a very slender splint-like bone, which extends about as far as the middle of the radius. In all species a detached sesamoid bone exists in the tendon of the triceps muscle, and is generally found in skeletons. The radius is very long, in some species as long as the head and body. The proximal row of the carpus consists of a single bone (the united scaphoid, lunar, and cuneiform bones), which, with the extremity of the radius, forms the radio-carpal joint; in the distal row the trapezium, trapezoid, and os magnum vary much in size in the different families ; the unciform appears to be the most constant, and the pisiform is generally very small. It will be necessary to again refer to this subject when dealing with the diagnostic characters of the suborders. The manus is, in all the species, composed of five digits. The first, fourth, and fifth consist each of a metacarpal bone and two osseous phalanges ; in the second and third the number of phalanges is different in certain families. The first digit the pollex always terminates in a claw, which, with the proximal phalanx, is most developed in the frugivorous species. In most of the species of the frugivorous Pteropodid-se the second digit is also provided with a claw, but in all other Bats this and the remaining digits are unarmed. In the genus Trisenops alone a very peculiar short bony process projects from the outer side of the proximal extremity of the terminal phalanx of the fourth digit. The relative development of the digits and their phalanges will be specially treated of under each family. As might be expected from the small size of the posterior limbs, the pelvic girdle is very weak. The iliac bones are long and narrow. In most species the pubic bones of opposite sides are very loosely united in front in males ; in females they are widely separated; in the family Rhinolophidaz alone do these bones form a symphysis. The eminentia ileo-pectinea develops in all species a long pectineal process, which in the subfamily Phyllorhininse alone is continued forwards to the anterior extremity of the ilium (vide infra, p. 412), forming a preacetabular foramen which is unique among mammals. The acetabulum is small and directed outwards, and slightly upwards, and with this is related the peculiar position of the hind limb described above as one of the chief characteristics of the order. The femur is slender and cylindrical, with a small head and very short neck, and scarcely differs in form throughout the species. The bones of the leg and foot are more variable ; in the subfamily Molossinse alone is there a well-developed fibula ; in all other species this bone is either very slender or cartilaginous and ligamentous in its upper third, or reduced to a small bony process above the heel, as in Megaderma, or altogether absent, as in Nyderis. The foot consists of a very short tarsus, and of slender, laterally compressed toes, with much curved claws. The first digit is composed of a metacarpal bone, a proximal and an ungual phalanx, and is slightly shorter than ths other four toes, which have each an additional phalanx, except in the subfamily Phyllorhininse, and in the anomalous genera Thyroptera and Myxopoda, where all the toes have the same number of phalanges as the first digit, and are equal to it in length. In the very remark able genus Cheiromeles the first digit is thumb-like and separated from the others ; and in the Molossi the first and fifth digits are much thicker than the intermediate toes. The muscular system, as might be expected, exhibits few striking differences throughout the species. The most noticeable peculiarities in the myology of the order consist in the separated bands or slips into which the platysma is divided, and in the remarkable muscle termed occipito- pollicalis, which extends from the occipital bone to the base of the terminal phalanx of the pollex (see Macalister, &quot; Myology of the Chiroptera&quot; Phil. Trans. Roy. Soc., 1872). Although, as above mentioned, the brain presents a low type of organization, yet probably no animals possess so delicate sense of touch as the Chiroptera. It is undoubt edly this perceptive power which enabled the individuals deprived of sight, hearing, and smell, in Spallanzani s well- known experiments, to avoid the numerous threads hung across the rooms in which they were permitted to fly about. In the common Bats the tactile organs evidently exist, not only in the delicate vibrissaj which spring from the sides of the muzzle, but also in the highly sensitive and widely extended integumentary structures entering into the forma tion of the wing-membranes and ear-conchs, while in many other species, notably in the tropical Rhinolophine and Phyllostomine Bats, peculiar foliaceous cutaneous expan sions surrounding the nasal apertures or extending back wards behind them are superadded (vide infra). These structures, collectively known as the &quot; nose-leaf &quot; (whence the term &quot; leaf-nosed Bats &quot;), have been shown by tho present writer (who has traced their gradual development in different species) to* be made up partly of the extended and thickened marginal integument of the nostrils, and partly of the highly differentiated glandular eminences occupying the sides of the muzzle, in which, in all the common Bats, the vibrissae are implanted. In all species of leaf -nosed Bats, and especially in th? JRhinolophidx, in which the nasal appendages reach their highest development, the superior maxillary division of the fifth nerve is of. remarkably large calibre. The nasal branch of this nerve, which is given off immediately beyond the infra-orbital foramen, is by far the largest por tion, the palpebral and labial branches consisting of a few slender nerve fibres only. This branch passes forwards and upwards on the sides of the superior maxillary bone, but soon spreads out into numerous filaments which pass into the muscles and integument above, and into the base of the nose-leaf. The nerve supply of the nose-leaf is further considerably augmented by the large nasal branch of the ophthalmic division of the fifth nerve. While the many foliations, elevations, and depressions which vary the form of the nose-leaf also greatly increase the sensory surface so abundantly supplied by the fifth nerve, and in rapid flight intensify the vibrations conveyed to it, the great number of sweat and oil glands which enter into its structure perform an important function, analogous to that of the glands of the auditory canal in relation to the membrana tympani, in maintaining its surface in a highly sensitive condition. The nasal appendages of Chiroptera, then, may be regarded as performing the office of an organ of a very exalted sense of touch standing in the same relation to tho nasal branches of the sensory divisions of the fifth nerve as the aural apparatus to the auditory nerve ; for, as tho latter organ collects and transmits the waves of sound, so the former receives impressions arising from vibrations communicated to the air by approaching objects. In no order of mammals is the ear-conch so greatly developed or so variable in form ; in most of the insecti vorous species the ears are longer than the head, while in some, as in the common Long-eared Bat (Plecotus auritus), their length nearly equals that of the head and body. The form of the conch is very characteristic in each ^ of the families ; in most the tragus is remarkably large, in some extending nearly to the outer margin of the conch; its office appears to be to cause undulations in the waves of sound, and so intensify and prolong them. It is worthy of