The spirometer popularized notions of 'race corrections' and 'ethnic adjustments,' which suggested that black individuals have weaker lungs than white individuals. For example, Thomas Jefferson noted physical distinctions between different races such as a 'difference in the structure of the pulmonary apparatus,' which made black individuals 'more tolerant of heat and less so of cold, than the whites.' Jefferson's theories encouraged speculation on the natural conditioning of blacks for agricultural labor on southern plantations in the U.S. Samuel Cartwright, a slavery apologist and plantation owner, used the spirometer to make the claim that black people consumed less oxygen than white people in addition to racial 'peculiarities' he laid out in the "New Orleans Medical and Surgical Journal" that described racial differences in the respiratory system and the implication of them on labor.