Diagrams, heartbeats by J A [John Alexander] MacWilliam Four diagrams showing the rhythm of the heart during MacWilliam's investigations into the effects of increased arterial pressure on the mammalian heart. Subject: Physiology Received 30 May 1888. Read 7 June 1888. Communicated by Michael Foster These diagrams were published in volume 44 of the Proceedings of the Royal Society alongside the paper 'On the effects of increased arterial pressure on the mammalian heart'. 1888