(Previous in the series: Introduction, Overview, On Species, Peculiarities, More Peculiarities, Peculiar Brains, Peculiar Blood, Tiedemann on Brains. Full text of Cartwright’s paper can be found here in three parts on pages 64, 209, 331 and with a response to critics on page 504. The full text of Tiedemann’s paper here as a PDF.)
Cartwright’s position that black people have fundamentally smaller brains than white people simply does not withstand scrutiny, deriving as it does from an authority, Soemmerring, working from isolated samples and not borne out by Tiedermann’s more extensive survey. His original claim that black people suffer from insufficiently oxygenated blood derives from nothing more than his anecdotal observations. This leaves him with one more claim, which I have mentioned before:
According to Soemmerring and other anatomists, who have dissected the negro, […] all the nerves going from the brain, as also the ganglionic system of nerves, are larger in proportion than in the white man. The nerves distributed to the muscles are an exception, being smaller than in the white race. Soemmerring remarks, that the negro’s brain has in a great measure run into nerves.
The final remark, from Soemmerring via Cartwright, at least has the benefit of evocative prose and so has often come to mind as I write these posts. But as I said yesterday, Tiedermann evaluated Soemmerring here as well:
Soemmerring was the first who compared the size of the brain with the thickness of the nerves. He says that the nerves on the basis of the brain are somewhat thicker in the Negro than in the European. This difference seemed to him particularly remarkable in the olfactory and optic nerves, and in the nervi quinti. This difference is not visible in the nerves of the brain of the Negro Honore (Plate XXXII.); they are quite as small as the nerves in European brains: nor did I find any difference in the brain of the Bosjes woman, nor in the two Negro brains in the Museum of Comparative Anatomy at Paris. We cannot, therefore, allow that the Negro brain is smaller than that of the European compared with the size of the nerves, or that the nerves of the Negro are thicker than those of the European.
Tiedermann has far more limited samples of brain and nerve tissue to evaluate. Soft flesh does not keep as well as hard bone and so one can only expect it on hand in smaller quantities. But the four specimens Tiedermann had access to do not match Soemmerring’s claim.
Tiedermann examines the brains he has in great detail, comparing sizes by various other measures, further supporting his position that black and white brains have no fundamental differences. He ultimately concludes:
I. The Brain of a Negro is upon the whole quite as large as that of the European and other human races. The weight of the brain, its dimensions, and the capacity of the cavum cranii prove this fact. Many anatomists have also incorrectly asserted that Europeans have a larger brain than Negroes.
II. The nerves of the Negro, relative to the size of the brain, are not thicker than those of Europeans, as Soemmerring and his followers have said.
III. The outward form of the spinal cord, the medulla oblongata, the cerebellum, and cerebrum of the Negro show no important difference from that of the European.
IV. Nor does the inward structure, the order of the cortical and medullary substance, nor the inward organization of the interior of the Negro brain show any difference from that of the European.
Tiedermann concludes with an affirmation of the equal intellectual abilities of people black and white alike, remarking with full knowledge of Cartwright’s antecedents, that
Some have even believed the falsely supposed natural inferiority of the intellectual and moral faculties of the Ethiopian race, to be an excuse for slavery.
He certainly had Cartwright’s number. Taken together with his measurements of skulls, Tiedemann’s dissections leave Cartwright without a scientific leg to stand on.