5. Certain Odours. There is a place in Scotland where madness is sometimes induced by the fumes of lead. Patients who are affected with it bite their hands, and tear their flesh upon the other parts of their bodies. It is called by the country people mill-reck. Dr. Prost describes a furious grade of madness in Peru, brought on by a mineral exhalation, but he does not mention the metal from which it is derived. From among many other facts that might be mentioned, to show the connection of odours with a morbid state of mind, I shall mention one more. An ingeneous dyer, in this city, informed me that he often observed the men who were employed in dying blue of which colour indigo is the basis, to become peevish, and low spirited, and never even to hum a tune, while engaged at their work.
[Chapter 2, pp31-32]