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 is 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. English translation, Edinburgh: The Alembic Club, 1907. Digital facsimile of the 1907 translation from the Internet Archive at this link. Digital facsimile of the 1674 edition from Google Books at this link. In the second edition of the Tractatus quinque Mayow recorded a case of mitral stenosis, probably the first description. Reprinted in his Medico-physical works, Edinburgh, 1907, pp. 295-97.