OSSEOUS SYSTEM OF MAMMALIA. 53 



ring of the first vertebra fits the margin of the foramen, to the back part 

 of which a process of the second, to be described hereafter, is attached, 

 the rest following, one below another, there will be a slight tendency of 

 the skull to fall forward (as it does when we sleep sitting upright, the 

 muscles being then relaxed), requiring a proportionate degree of muscular 

 effort to counteract it. In the Ape tribe the foramen magnum, and, conse- 

 quently, the condyles, are placed far more backward than in the human 

 subject. The skull of an adult Monkey, purposely examined, measuring 

 from the fore-teeth to the occiput four inches and a half, has the condyles 

 only one inch from the posterior margin of the latter. In younger exam- 

 ples, owing to the imperfect development of the upper jaw, the distance 

 from the fore-teeth to the condyles is comparatively less : in all, however, 

 it is very considerable, so as to destroy even an approach towards an 

 equipoise of the skull on the vertebral column. In the adult Orang, the 

 measurement from the alveolar process of the front teeth to the posterior 

 edge of the occipital condyle is 6| inches, and from the posterior edge of 

 the condyle to a vertical line, parallel with the extent of the occiput, less 

 than two inches. In the adult (female) Chimpanzee, the same admeasure- 

 ments are respectively 5j and 1|, or nearly two inches. When we turn 

 to the skulls of animals of other orders, we find that the condyles have 

 retired to the extreme posterior limits of the cranium, and that their 

 aspect is partly basal, partly posterior, the head being suspended from 

 the end of the neck, whether this be carried horizontal, or, as in the 

 Camel, vertical ; the weight of the whole head and face being anterior to 

 the first vertebra. Hence, as in the Ox, where the head is ponderous, and 

 the neck, in order to allow of grazing, necessarily long, the spinous pro- 

 cesses of the cervical and dorsal vertebrae are of vast size and strength, 

 and not only serve for the attachment of voluminous muscles of enormous 

 power, but also for the insertion of a strong elastic ligament (ligamentum 

 nuchae), which proceeds along them from the back of the skull, the strain 

 of which it materially serves to support. In the neck of the Bull we 

 see a fine example of vast power, nor less so in the neck of the Wapiti 

 deer, which wields his antlers, weighing from forty to sixty pounds, with 



muscles, and other soft parts. This inclination of the head forward is counteracted, in the living body, 

 by the extensor muscles ; and their constant exertion is necessary for maintaining the head in equi- 

 librio on the vertebral column. Whenever their action is suspended, as in the case of a person falling 

 asleep, in the erect attitude, with the head unsupported, that part, abandoned to the force of gravity, 

 immediately nods forward" (Lect. pp. 175-6-7). Richerand says, the articulation of the head to the 

 vertebral column being nearer to the occiput than to the cranium, and not corresponding to its centre 

 of gravity, its own weight is sufficient to make it fall on the forepart of the chest (Siemens de Phys. 

 p. 407). And again : though the articulation of the head to the cervical column, does not correspond 

 either to its centre of magnitude, or to its centre of gravity, and though it is nearer to the occiput than 

 to the chin, its distance from the latter is much smaller than in the Monkey, and other animals 

 ( Ibid. p. 411): Magendie also fortifies the assertion of Mr. Lawrence, by stating,'.that the point of support 

 being nearer to the occiput than to the anterior part of the face, the head tends, by its weight, to fall 

 forward, but is maintained in equilibrio by the action of those muscles which are attached to its 

 posterior part (Siemens de Phys. i. 362). 



