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Harvey Cushing and the regulation of blood pressure in giraffe, rat and man: introducing ‘Cushing’s mechanism’

The fundamental mechanism that underlies essential hypertension is a high total peripheral resistance. We review here possible origins of high total peripheral resistance in physiologically hypertensive giraffes, spontaneously hypertensive rats and humans with essential hypertension. We propose that a common link could be reduced brainstem perfusion, as first suggested by Cushing in 1901. Any tendency towards reduction of cerebral blood flow to the cardiovascular control centres in rest and sleep will be prevented by activation of a response arising in

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How giraffes prevent oedema

An upright giraffe, by analogy with humans, ought to suffer massive oedema in its feet; moreover, when it lowers its head to drink, the blood should rush down into it and be unable to flow up again. New pressure measurements reported on page 59 of this issue by Hargens et al. Show why neither of these things happens, and also contain some surprising observations of highly variable venous pressure (P.) in the leg and of a counter-gravitational gradient of P.

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Carotid Haemodynamics in the Giraffe

In a research letter to this journal on the physiology of the giraffe, McCalden et al. suggested that cranial blood flow in the giraffe is regulated by an autoregulatory response of the cranial vasculature. Their conclusion was based on two points: 1) that carotid flow remains constant over a wide range of carotid pressures, and 2) that the giraffe exhibits certain postural behaviour. The argument for (2) is that giraffes always remain resting sternally for a few seconds before standing

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