The Diseased and Peculiar Science of Dr. Samuel A. Cartwright (Tiedemann on Brains)

Samuel A. Cartwright

Samuel A. Cartwright

(Previous in the series: IntroductionOverviewOn Species,PeculiaritiesMore PeculiaritiesPeculiar Brains, Peculiar Blood. 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.)

Last time, I wrote a bit about how Louisiana physician Samuel A. Cartwright claimed to discover, not via chemical analysis, not via anatomical investigation, but by simple anecdote that black people simply did not get enough oxygen to their brains. That, combined with just how small a brain a black person had, made the whole species unable to govern themselves and best suited to slavery. But those same small, oxygen-starved brains made them prone to mental illnesses that caused a rejection of slavery.

I left the discussion of oxygenation of the blood off with a note about the importance of representative samples that I want to repeat by way of a bad example of my own: Based on my current observations, the human species consists of men thirty-two years of age who require corrective lenses. Fifty percent wear beards. I made the observations with my own eyes from a sample readily at hand: myself and a friend. While he and I constitute a sample of humanity, we do not constitute a representative sample. Drawing generalizations from us just leaves one with absurdity, like the notion that no human women or people over the age of thirty-two exist.

Friedrich Tiedemann

Friedrich Tiedemann

That said, I want to return to Cartwright’s brain measurements. Here I rely on the German anatomist Friedrich Tiedemann (1781-1861), who investigated the matter of brain size and nervous system arrangement and published in Philosophical Transactions of the Royal Society of London, volume 126, in 1836. (Full text here as a PDF.)

Tiedemann examined, among others, the work of Cartwright’s go-to anatomist Soemmerring. While he opposed slavery, Tiedemann did not write a political hit piece aimed at Soemmerring and those who followed him. He took the matters of brain size and nervous system configuration as questions of science. There he found many flaws in his predecessors’ work:

they neither take any notice of the size and weight, nor the age and sex of the bodies, the brains of which they examined; and, lastly, they weighed far too few to draw any general conclusion.

Tiedemann wrote in English, but his native German shows through. To put it more concisely: they had an insufficient sample size. Tiedemann too had mostly European brains available to him, but did receive one black person’s brain. The man died of smallpox and Tiedemann’s son-in-law and son dissected him and sent the brain along, preserved in alcohol. One wonders what the postman said.

To his measurements of the organ itself, Tiedemann added proxy measures from forty-one skulls of certain ethnicity he had available, filling them with dry millet seed and comparing the weight of the whole with and without the seed to learn their capacities. His samples range from native Africans living in Africa to slaves from Suriname and North America. He compared those to seventy-one skulls of Europeans ranging from Don Cossacks and Turks to Finns, Prussians, Irish, Poles, Italians, and Spaniards. Going still farther, he measured the capacities of Asian, American Indian, and subcontinental Indian skulls as well. His findings, backed by pages of tables showing the figures for each skull:

It is evident from the comparison of the capacity of the cavum cranii of the Negro with that of the European, Mongolian, American, and Malayan, that the activity of the skull of the Negro, in general, is not smaller than that of the European and other human races.

I don’t know that Cartwright read Tiedemann’s paper, but it antedates his writing. He shows an awareness of other European writers  who differ but does not mention Tiedemann and dismisses the others as writing for political, not scientific motives. Whether Cartwright knew Tiedemann and ignored him or did not know him at all, I must leave to his biographers.

In any case, Tiedemann’s skull survey, combined with the inadequate samples of Cartwright’s authorities, fatally undermine the keystone of the Louisiana physician’s thesis: Black people simply do not have radically smaller brains. Nor can we take seriously his anecdote-driven case for inadequate oxygenation of their blood. But Cartwright might cling to one more peculiarity, that black people have much denser peripheral nervous systems than white people have. There too Cartwright relies on Soemmerring and there too Tiedemann looked into matters. More on that tomorrow.

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4 comments on “The Diseased and Peculiar Science of Dr. Samuel A. Cartwright (Tiedemann on Brains)

  1. Good stuff. Could you please tell me where you got the picture of Samuel Cartwright?

  2. kirbmarc says:

    Excellent analysis of the pseudoscience of Cartwright. Do you think that Cartwright might have known he was wrong, but lied nevertheless or did he genuinely believe what he wrote?

    In either case, it’s a pretty horrid page in the history of science, and it shows one of the dangers of biases and anecdotal evidence; they lead you to pervert the scientific effort to support your ideology.

    • Without knowing more about the man himself, I really can’t say for sure. He had, for his time, a very good medical education. The notion that black people constituted a separate species was current then current, though I think only supported by a minority of scientists. Other scientists, like Tiedemann, knew better. Cartwright knows opposing opinion exists, since he dismisses it in his paper, but he didn’t name Tiedemann among those he dismissed. I’m not sure now (It’s been more than a year since I read his work.) if he named any opposition figures. If he had, one could look into those and see if they had compelling cases (They might not. Every position generates bad arguments in its favor, whether it has good ones or not.) then we could presume he knew them from the references.

      If he knew of good work against his thesis and the best he could come up with was that the scientists opposing him were a bunch of hacks, that definitely puts him in the lying or blinded by ideology category. But Cartwright did not have the internet and communication, especially internationally, was slower and more expensive back then. I don’t know what sort of connection a man living in Louisiana would have had with, say, the British scientific establishment that published Tiedemann’s paper. He might not have had it in his power to do some kind of review of the literature and dig up a paper from a decade or so prior.

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