Memoir on the gorilla (Troglodytes Gorilla, savage). / by Richard Owen.

  • Owen, Richard, 1804-1892.
Date:
1865
Catalogue details

Licence: Public Domain Mark

Credit: Memoir on the gorilla (Troglodytes Gorilla, savage). / by Richard Owen. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    31/94 (page 23)
    the frontal, has no existence in the Gorilla, and the fossa for the ' natiform protube- rances ' (n, PI. XL) of the cerebral hemispheres is much less deep ; so that the division of the prosencephalic compartment into the fossa for the anterior, and that for the middle, lobes of the cerebrum is so feebly indicated in the Gorilla, that we may safely aver it would not have been recognizable without the indications afforded by the better-developed boundaries in the Human subject. By the light of the same com- parison we are able to recognize, reciprocally, through the better-defined rhinence- phalic compartment in the Gorilla and Orang, the true nature of that almost effaced primary natural division of the cranial cavity in our own species. In the Gorilla the boundary of the epencephalic chamber is more complete and defi- nite than in Man, the tentorial ridge being continued from the petrosal (i6, PI. XI.) outwards and backwards to the exoccipital (2). The epencephalic compartment of the cranium, which, in Man, is bounded behind by the impression of the lateral sinus in the higher races,—which impression is feebly, if at all, marked in Papuan skulls,—is relatively larger and especially deeper in all the races than in the Gorilla ; and this greater depth, with the more central position of the foramen magnum at the base of the skull, is associated with a production of the walls of the epencephalic compartment downward in an infundibular form to the foramen magnum, and with a remarkable difference in the aspect of the plane of the basioccipital and basisphenoid, in the Human cranium. The posterior boundary of the epencephalic compartment is only half an inch above the foramen magnum in the Gorilla, whilst in the Papuan it is one inch two-thirds, and in the European nearly two inches ; and this difference depends riot only on the greater vertical extent of the cerebellum, but on the above-mentioned characteristic position of the foramen magnum which relates to the erect posture and gait of the Human species. By no method, indeed, is the strongly marked distinction afforded by the foramen magnum between Man and the highest Quadrumana so clearly demonstrated as by the vertical bisection of the skull here described. In the first place, as to the size of the foramen, it is, relatively to the capacity of the cranium, much larger in the Gorilla than in Man. Taking the antero-posterior diameter crossed by the section, we find this to be precisely the same in the skulls of the Gorilla and the Australian compared. The differ- ence in the aspect of the plane of the foramen (n -. -. - d) is, perhaps, best shown by comparing such plane with that of the bony palate (b b). And here may be noted the vaulted form of the roof of the mouth in Man, as shown by its greater longi- tudinal curve in Plate XII. than in Plates X. & XI. If a line drawn along the floor of the nostrils be intersected by one drawn parallel with the lower surface of the basioccipital and basisphenoid, an angle of 45° is inter- cepted in the Human cranium ; whilst in the Gorilla the lower plane of the basioccipital (1) and basisphenoid (5) and the plane of the floor of the nostrils (20, 21) are parallel. In the Gorilla the precondyloid canal is relatively smaller than in Man; and, in the