GM: "Mayow was the first to locate the seat of animal heat in the muscles; he discovered the double articulation of the ribs with the spine and came near to discovering oxygen in his suggestion that the object of breathing was to abstract from the air a definite group of life-giving 'particles'. He was the first to make the definite suggestion that it was only a special fraction of the air that is of use in respiration. His Tractatus, embodying all his brilliant conclusions, is one of the best English medical classics." The portrait frontispiece, which is illustrated above, is attributed by Fulton to William Faithorne.