OSSEOUS SYSTEM. 9 



cranial cavity for the lodgement of the cerebrum and cerebellum are 

 in many Mammalia, e. g. the Dolphin, Horse, Seal, Cat, &c., sepa- 

 rated by a bony tentorium prolonged inward from the posterior part 

 of the parietal bones. A bony falx, as in the Ornithorynchus is sel- 

 dom met with. The openings for the nerves exhibit various rela- 

 tions, those which are separated in Man sometimes coalescing into 

 single apertures, others, on the contrary, remaining distinct, as the 

 foramina incisiva. These intermaxillary apertures are particularly 

 laige in the Ruminantia, the Ornithorynchus, &c., but small in the 

 Apes, and completely absent in the Cetacea. 



The comparison of the form of the skull of the higher Apes with 

 that of Man is a subject of much interest. Young Orang-utangs 

 and Chimpanzees, like all young animals, have a very rounded form 

 of skull ; and owing to the slight development of the jaws, the 

 relation of the cranial to the facial portion approximates more 

 closely to that of the human subject ; but, as they grow up, very 

 strong muscular ridges are developed from the skull, and the pro- 

 portion of these parts then becomes equal. The cranium of a full 

 grown Orang-utang nearly equals that of Man in size, but the ca- 

 pacity of its cavity is considerably less. The skull of the Chim- 

 panzee ranks next to the human cranium, and there are even forms 

 of the latter, as of persons born deficient in brain and intellect, 

 which sink to the same proportions as those of the Chimpanzee. 

 The distinguishing osteological characters in the skull of the Orangs 

 (S. satyrus arid troglodytes) from that of Man are as follows : There 

 is a remarkable interval between the canine and incisor teeth in the 

 upper, and between th canine and molar teeth in the lower jaw ; 

 the original development of the intermaxillaries is much more 

 conspicuous, o^d the foramina incisiva are removed farther back 

 from the incisor teeth ; the foramen magnum, which in Man falls 

 immediately behind a median line drawn transversely across the 

 base of the skull, lies much further back and is more slanting ; the 

 articulating condyles of the occipital are smaller ; the petrous bone 

 and the jaws are much more strongly developed ; the nasal bones 

 are flattened and blended together ; the mastoid and styloid pro- 

 cesses of the temporal, and the crista 1 galli of the ethmoid are 

 wanting. 



The Vertebral Column exhibits great constancy in the number 

 of vertebrae in its cervical region. There are most generally seven ; 

 Manatus and Rytina have six, the three-toed Sloth has nine cervical 

 vertebrae, both of these being very rare exceptions. The cervical 



