Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/179

Rh ANATOMY.] tubercle. In tlie rest of the Simiadce this ridge is want ing, but it reappears in Aides and Mycetes amongst the G ebidce. In the Hapalince the tubercles of the molars are more produced and sharp-pointed, in harmony with their decidedly insectivorous habits. The last lower molar may be reduced or much enlarged as compared with the others. Thus in Cercopitkecus talapoin it has but three tubercles, while in the Macaci and Cynocephali it is very large, and has five well-developed cusps. The number of milk teeth is as in man, save that the Cebidce have an additional milk molar. In general the canines are the last teeth to be cut of the permanent dentition. Their cutting sometimes causes such constitutional disturbance as to produce con vulsions and death. In the gibbons, however, the canines accompany, if they do not precede, the appearance of the hindmost molar, while in the orang they at least sometimes make their appearance before that grinder. ORGANS OF NUTRITION AND EXCRETION. The alimentary, circulating, and excretory organs of apes closely resemble those of man. The mouth is always guarded by lips, which, though generally thin, are often very mobile and extensible, the lower lip having no frrenum in the orang, and this is also absent in Cebus, though it may be present in other forms, as, e.g., in Troglodytes and Cynoceplialus. The tongue is much longer relatively in most apes than in man ; but it may closely resemble his, as does that of the orang, in which the circumvallate papillae are collected in a V-shaped aggregation, while there may be only two such papillae, as in Cynoceplialus and Ateles. In Hylobates the tongue is in this respect man-like ; yet in that genus we first meet with a sub-lingual process (which becomes much larger in the lower apes), in the form of a little conical bifid membrane. This structure is formed by the union of the processes upon which open the sub-maxillary ducts processes much elongated in the chimpanzee, though man-like in the orang. The uvula is generally present, but becomes rudimentary in the Cebidce generally, though it exists as a relatively thick, short structure in Ilapale. It is long and pointed in SemnopitJiecus, and plainly visible in Hylobates and Troglodytes. On the other hand, in Simla it is disguised by the extensive development of the membranous edge of the velum palati on each side of it. The stomach is simple in all the apes except the Semno- pitkecince. It is especially human in shape in Hylobates, except that the pylorus is somewhat more elongated and distinct. It is of a rounded form in Pithecia, and in Hapale the cardiac orifice is exceptionally near to the pylorus. In the Semnopithecince the stomach is extremely sacculated, especially at the cardiac end, being, in fact, very like a colon spirally coiled. It is in the stomach of these apes that the oriental Bezoar stones are found. The intestine in apes is devoid of valvulce conniventes, but is always provided with a well-developed ccecum, though it is short and conical in Cynocephalus. Only in the Simiince do we find a vermiform appendix. The colon may be much longer relatively than in man, as in Simia and Troglodytes. It may be greatly sacculated, as in Hylobates; or devoid of sacculations, as in Cebus. As in foetal man, so in the lower apes, only the right extremity of the mesocolon is involved in the formation of the great omentum, the middle and left parts of the meso colon lying behind, and independent of the omentum. This is not, however, the case in the Simiincc, which are more like adult man in this respect. The liver may be very like man s, especially in Hylobates, the orang, and the chimpanzee; but in the gorilla both the right and left lobes are cleft by a fissure almost as 1G5 much as in Cynocephalus. In the Semnopithecince the liver is much divided, and it is placed obliquely to accom modate the sacculated stomach. The lateral lobes of the liver are in Hapale very much larger than the central lobe. The caudate lobe is very large in the Cebidce, especially in Ateles, and above all in Pithecia. There is always a gall bladder. The larynx is in many apes furnished with sac-like appendages. These are different in different species as regards number, size, and situation. They may be dilata tions of the laryngeal ventricle (opening into the larynx below the false vocal chords), as in Simia and Troglodytes. They may open above the false vocal chords so as to be, in fact, extensions of the thyro-hyoid membrane, as in Hylobates. There may be but a single median opening in the front part of that membrane at the base of the epi glottis, as in the Simiadce below the Simiince. There may be a single median opening at the back of the trachea, just below the cricoid cartilage, as in Ateles. There may be but a single sac, or there may be five, as sometimes in Mycetes. These may be enormous, meeting in the middle line in front, and extending down to the axillae, as in the gorilla and orang. A sac may occupy the cavity of the expanded body of the hyoid bone, as in Mycetes. The os hyoides has its basilar part generally somewhat more convex and enlarged than in man; but in Mycetes it becomes greatly enlarged and deeply excavated, so as to form a great bony bladder-like structure. The cornua of the hyoid are never entirely absent, but the anterior or lesser cornua may be so, as in Mycetes. The anterior cornua never exceed the posterior cornua in length; but they may be (e.g., in Cercopithecus) more largely developed relatively than in man, and they may even be jointed structures, as in Lagothrix. The lungs have generally the form of those of man ; but the right lung may have four lobes, as, e.g., in Hylobates. The great arterial trunks in Simia and Troglodytes are arranged as in man. In Hylobates and the lower apes, however, the left carotid may take its origin from the innominate artery. THE GENERATIVE ORGANS. The generative organs are, in common with the other parts of the body, formed on the same model as in the human species. The/&amp;gt; s is pendulous, i.e., hangs freely, instead of being (as in the dog) bound to the ventral sur face of the abdomen. The prepuce, however, is without a frsenurn. The testes are relatively large, and descend into a scrotum. In some species, however, they do not descend so much as they do in man, but remain just outside the inguinal ring, and are thus placed rather beside than beneath the penis. These parts, as has been said, are brightly coloured in some of the lower Simiadce. The penis is furnished with a bone in all the apes below the Anthro poid ones, and probably in the latter also, since the chim panzee has one about one-third of an inch long and gristly at each end. In all apes the uterus is single, and not two- horned; but it is more elongated relatively in monkeys than in the human species. The clitoris is well-developed, but boneless in the Simiadce, and is large even in Troglo dytes niger. In the Cebidce it contains a bone; and in some genera, especially in the Cebince, it is enormously developed, so as to be very easily mistaken for a penis. In Ateles, however, its length is mainly due to its extremely elongated prepuce. The placenta of apes is discoidal and deciduate, and is generally bilobcd. Sometimes, however, as in Mycetes, it is single. It is especially thick in proportion in the HapaliKce. In the Simiadce there is but one umbilical vein, but in the Cebidce there are two.