Complex sentence: This must be corrected for measuring the in human breath by measuring its infra-red absorptive power was established as a reliable technique by John Tyndall in 1864, though 19th and early 20th century devices were too cumbersome for everyday clinical use.
Split into simpler sentences: This must be corrected for measuring the in human breath by measuring its infra-red absorptive power. This was established as a reliable technique by John Tyndall in 1864, though 19th and early 20th century devices were too cumbersome for everyday clinical use.