A treatise on diet, or the management of human life; by physicians called the six non-naturals, viz. I. The air. II. Food. III. Excretions and retentions. IV. Motion and rest. V. Sleep and watching. VI. The affections of the mind. Intended As an Inquiry into the Causes of Diseases in general, and in particular of those most common in London. Addressed to the inhabitants of this metropolis. By Francis de Valangin, M. D. Of the Royal College of Physicians, London