Translation of a letter, from Antoni van Leeuwenhoek to the Royal Society Stating that balsam, if rubbed onto the chest, cannot pass into the lungs;account of apparatus, designed by Leeuwenhoek to inhale smoke and vapour; observations of the blood vessels in a sheep's lung; observations of Leeuwenhoek's phlegm; theory that cold air can harm the lungs Original letter is EL/L3/42 English translation printed in 'Philosophical Transactions', vol 23, no 279, p 1143 1702