From Francis Darwin [before 22 August 1872]1
Sutton says that the monkeys are often sick but he cannot say whether they do it voluntarily or not—2 But as they often do it when it good health it looks as if they could I think
Yrs affec | F Darwin
Sutton says monkeys often vomit, but cannot say whether they do it voluntarily.
Please cite as
Darwin Correspondence Project, “Letter no. 5556,” accessed on 25 April 2017, http://www.darwinproject.ac.uk/DCP-LETT-5556