HKB
Primates and from the mammalia generally as a distinct SUB-CLASS, thus departing farther from the classification of Blumenbach and Cuvier than they had ventured to do from that of Linnaeus.
The proposed innovation was based chiefly on three cerebral characters belonging, it was alleged, exclusively to Man and thus described in the following passages of a memoir communicated to the Linnaean Society in 1857, in which all the mammalia were divided, according to the structure of the brain, into four sub-classes, represented by the kangaroo, the beaver, the ape, and Man respectively:--
"In Man, the brain presents an ascensive step in development, higher and more strongly marked than that by which the preceding sub-class was distinguished from the one below it. Not only do the cerebral hemispheres overlap the olfactory lobes and cerebellum, but they extend in advance of the one and farther back than the other. Their posterior development is so marked that anatomists have assigned to that part the character of a third lobe; it is peculiar to the genus Homo, and equally peculiar is the 'posterior horn of the lateral ventricle' and the 'hippocampus minor' which characterises the hind-lobe of each hemisphere. The superficial grey matter of the cerebrum, through the number and depth of its convolutions, attains its maximum of extent in Man.
"Peculiar mental powers are associated with this highest form of brain, and their consequences wonderfully illustrate the value of the cerebral character; according to my estimate of which I am led to regard the genus Homo as not merely a representative of a distinct order, but of a distinct sub-class of the mammalia, for which I propose the name of 'Archencephala.'"*
(* Owen, "Proceedings of the Linnaean Society" London volume 8 page 20.)
The above definition is accompanied in the same memoir by the following note:--"Not being able to appreciate, or conceive, of the distinction between the psychical phenomena of a chimpanzee and of a Boschisman, or of an Aztec with arrested brain-growth, as being of a nature so essential as to preclude a comparison between them, or as being other than a difference of degree, I cannot shut my eyes to the significance of that all-pervading similitude of structure--every tooth, every bone, strictly homologous--which makes the determination of the difference between Homo and Pithecus the anatomist's difficulty; and therefore, with every respect for the author of the Records of Creation,* I follow Linnaeus and Cuvier in regarding mankind as a legitimate subject of zoological comparison and classification."
(* The late Archbishop of Canterbury, Dr. Sumner.)
(FIGURE 54. UPPER SURFACE OF BRAIN OF CHIMPANZEE, DISTORTED (FROM SCHROEDER VAN DER KOLK AND VROLIK.) Scale half the diameter of the natural size.
A. Left cerebral hemisphere. B. Right cerebral hemisphere. C. Cerebellum displaced.)
(FIGURE 55. SIDE VIEW OF BRAIN OF CHIMPANZEE, DISTORTED (FROM SCHROEDER VAN DER KOLK AND VROLIK.) Scale half the diameter of the natural size.
e. The extension of the displaced cerebellum beyond the cerebrum at d.)
(FIGURE 56. CORRECT SIDE VIEW OF CHIMPANZEE'S BRAIN (FROM GRATIOLET). Scale half the diameter of the natural size.
d. Backward extension of the cerebrum, beyond the cerebellum at e. f. Fissure of Sylvius.)
(FIGURE 57. CORRECT VIEW OF UPPER SURFACE OF CHIMPANZEE'S BRAIN (FROM GRATIOLET), in which the cerebrum covers and conceals the cerebellum. Scale half the diameter of the natural size.)
(FIGURE 58. SIDE VIEW OF HUMAN BRAIN (FROM GRATIOLET), NAMELY, THAT OF THE BUSHWOMAN CALLED THE HOTTENTOT VENUS. Scale half the diameter of the natural size.
A. Left cerebral hemisphere. C. Cerebellum. ff. Fissure of Sylvius.)
To illustrate the difference between the human and Simian brain, Professor Owen gave figures of the negro's brain as represented by Tiedemann, an original one of a South American monkey, Midas rufimanus, and one of the chimpanzee (Figure 54), from a memoir published in 1849 by MM. Schroeder van der Kolk and M. Vrolik.*
(* "Comptes rendus de l'Academie Royale des Sciences" Amsterdam volume 13.)