5 Pages in Charles Darwin's Library associated with "physical conditions - yawning"

De la physionomie et des mouvements d'expression
By: Gratiolet, Pierre,
Publication info: Paris, J. Hetzel, 1865
Pages: Page 125 Page 126 Page 232
Elements of physiology
By: Müller, Johannes, - Baly, William,
Publication info: London, Taylor & Walton, 1838-1842
Volume: v.1
Pages: Page 353
Wissenschaftliches System der Mimik und Physiognomik
By: Piderit, T.
Publication info: Detmold, Klingenberg, 1867
Pages: Page 79