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I was pleased to see the reference to the Blazek sisters in Dr E Scott Sills' letter (March 2005 JRSM1). These ladies, who made remarkable adaptations to their disability, should indeed not be forgotten, not only for their obstetric history, but as having provided one of the foundation stones of endocrinology. The 'official' report of their case in a now obscure Bohemian journal does not contribute to physiology, but a visiting German physician, Dr Karl Basch, reported in Deutsche Medizinische Wochenschrift (1910) that, when Rosa breastfed her baby, Josepha also lactated. He drew the conclusion—just after Bayliss and Starling's paper reporting the discovery of secretin and contrary to then accepted belief that lactation was controlled by the nervous system—that lactation must be controlled by something circulating in the blood, since that was the only functional connection between the two individuals.
In subsequent decades the principle underlying Basch's observation was put to extensive use in laboratory animals, usually rats, surgically united in 'parabiosis' and developing a shared capillary circulation, and the pharmacodynamics that determine whether substances cross from one individual to the other were unravelled. Notable areas of study relevant to medicine include elucidation of the control of gonadal hormone secretion by the pituitary and the discovery of erythropoietin. I used the technique in the 1950s to achieve the first demonstration of the function of (I now believe) leptin in the feedback control of food intake: rats in parabiosis with obese partners (made obese in several ways) greatly reduced their food intake and became extremely thin. I wonder whether I shall see this observation contribute to medicine!