Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/170

Rh 156 APE [ANATOMY 11. Lagofhrix. Form rather robust; limbs moderate; fur woolly; internasal septum as broad as usual; thumb well developed; tail distally naked beneath. 12. Ccbus. Form rather robust; limbs moderate ; fur not woolly ; internasal septum as broad as usual; thumb well developed; tail not naked beneath distally. Sub-Family II. Mycetince. g M. 5 ; incisors vertical ; tail long and prehensile, naked beneath o distally ; hyoid bone enormous ; form of body massive ; thumb well developed; intern asal septum as broad as usual. 13. Mycctes. Sub-Family III. Pithcciincc. 3 M. - ; incisors inclined outwards distally ; tail long or short, o never prehensile ; hyoid bone&quot; moderate ; thumb well developed ; internasal septum as broad as usual. 14. Pithecia. Tail long. 15. Brachyurus. Tail short. Sub-Family IV. NyctipUheciiwc. o M. 3 ; incisors vertical ; tail long, not prehensile ; hyoid bone o moderate ; thumb well developed. 16. Nyctijrithccus. Head rounded; eyes enormous; nostrils rather approximated. 17. Chrysothrix. Head exceedingly elongated; eyes large, closely approximated ; canines well developed ; hair of tail rather short. 18. Callithrix. Head small, depressed, and not elongated; nostrils widely separate ; canines small ; hair of tail elongated. Sub-Family V. Hapalince. 2 M. - ; incisors vertical ; tail long, not prehensile ; hyoid bone 2t moderate ; thumb elongated, not at all opposable ; hallux very small ; a long curved and pointed claw to all the digits, except the hallux. 19. Hapale. Lower incisors and canines of equal length. 20. Midas. Lower canines much longer than the lower incisors. THE ANATOMY OF APES. To describe generally the anatomy of apes would be, in fact, to describe in an elementary manner the general anatomy of man. It is necessary, therefore, here to assume that the reader has already an elementary know ledge of human anatomy, and to refer such readers as have not such knowledge to the article ANATOMY. THE EXTEKNAL FORM AND CLOTHING. The difference in bulk between the different members of the group (e.g. Troglodytes and Hapale) is extreme, being greater than that between a man and a common squirrel. The proportions of the body as regards the relative lengths of the two pairs of limbs one with the other, and both with that of the trunk, vary considerably. Both pairs may be much elongated, as in Ateles and Hylolates, and either sub-equally, as in the first of these genera, or with the arms very greatly in excess, as in the second. The legs may be excessively short, and the arms, at the same time, excessively long, as in the orang. Both pairs may be short and sub-equal, as often in the Cynopithecince. Only in the Nyctipitliecince and Hapalince does the excess in length of the lower limbs over the upper exceed or equal that which is found in man. The length of the tail presents some noteworthy points. At its first appear ance it is found at once at its greatest absolute length, and also greatly developed relatively, being about twice the length of the trunk. Its greatest relative length is, how ever, attained in Ateles, where it reaches three times the length of the trunk. The constancy of the degree of its development varies much in different groups. In the greater number of genera it is long in all the species, and in some (Simia, Troglodytes, and Hylolates) it is absent in all In others it may be long or short, or completely absent, e.g., in Macacus. The form of the head presents great differences it may be rounded, as, e.g., in Ateles; produced vertically, as in Simia; drawn out posteriorly to an extreme degree, as in Chrysothrix; or anteriorly, as in Cynocephaliis. A production of the muzzle, necessitated by the presence of large teeth, exists already in Troglodytes; but in the baboons, not only is this prolongation carried much further, but the terminal position of the nostrils gives an emphatically dog-like aspect to the face. The eyes may be small compared with the size of the head, as in the baboons; they may, on the contrary, attain a relatively enormous size, as in Nyctipjitheciis. They are always forwardly directed, and never much more separated one from another than in man. They may, however, be much more closely approximated, as notably in Chrysothrix. The external ears are always well developed, and have very generally their postero-superior angle pointed. They may be large and small in the same genus, as in Troglo dytes. Only in the gorilla do we find present, even in a rudimentary condition, that soft depending portion of the human ear which is termed the &quot; lobule.&quot; The nose has scarcely ever more than a very slight pro minence, and yet an enormous development is to be met with in Semnopithecus nasalis ; while in S. roxellance we find a sharply prominent, though smaller and extremely upturned, nose. The hoolock gibbon also possesses a pro minent but slightly aquiline nose. The terminal position of the nostrils in Cynocephalus has been just mentioned. These apertures may be closely approximated, as in all the Simiadce, or they may be separated one from the other by a broad septum, as in the Cebidce, its breadth, however, varying somewhat in different genera, as, e.g., in Ateles and Eriodes, and in Callithrix and Nyctipithecus. The lips are generally thin, but may be very extensive, as in Simia. The hands are generally provided with thumbs, though these organs (as in Colobus and Ateles) may be represented only by small nailless tubercles. The thumb (pollex) is more human in its proportions in the chimpanzee than in any other of the highest apes. As compared with the length of the hand, it is most man-like in the lowest Cebidce, e.g., Chrysothrix and JIapaJe. In spite of greater relative length, however, it may but little merit the name of thumb, as it is but slightly opposable to the other digits in any of the Cebidce, and is not at all so in the Hapalince. The hallux (great toe) is never rudimentary like the pollex. It is never, as it often is in man, the longest digit of the foot, but is constantly the shortest one. As compared with the entire length of the foot, it is most human in the chimpanzee and some gibbons, and smallest of all in the orang, and next smallest in Hapale. More detailed proportions will be more appropriately given in speaking of the skeleton. Every digit is provided with a nail, except the hallux of the orang and those rudimentary tubercles already spoken of as representing thumbs in Ateles and Colobus. The nail of the hallux is flat in every species, but the other nails are never so flat as are the nails of man. The lateral compres sion of the nails becomes more strongly marked in some Cebidce, e.g., in Eriodes, but attains its extreme in the Ilapalincc, where every nail, except that of the hallux, assumes the form of a long, curved, and sharply-pointed claw. All the apes, without exception, differ from man in having the body almost entirely clothed with copious hair, and especiaUy in never having the back naked. In the gibbons, the Semnopithecince, and the Cynopithecince, naked spaces (ischiatic callosities} are present on that part of the