(C) The Anatomy of Apes (cont.)

The Organs of Nutrition and Excretion of the Ape

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 fraenum in the orang, and this is also absent in Cebus, though it may be present in other forms, as e.g., in Troglodytes and Cynocephalus.

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 Cynocephalus 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 Cebidae generally, though it exists as a relatively thick, short structure in Hapale. It is long and pointed in Semnopitchecus, and and plainly visible in Hylobates and Troglodytes. On the other hand, in Simia 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 Semnopithecinae. 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 Pitchecia, and in Hapale the cardiac orifice is exceptionally near to the pylorus. In the Semnopithecinae 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 valvulae conniventes, but is always provided with a well-developed caecum, though it is short and conical in Cynocephalus. Only in the Simiinae 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 mesocolon lying behind, and independent of the omentum. This is not, however, the case in the Simiinae 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 much as in Cynocephalus. In the Semnopithecinae the liver is much divided, and it is placed obliquely to accommodate 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 Cebidae, 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 dilatations 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 epiglottis, as in the Simidae below the Simiinae. 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 baldder-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 structure, 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.





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