This book deals with the part played by man's nervous system in mental and physical work and the interrelationship between these forms of work in the light of Pavlov's teaching on higher nervous activity. It also deals with the phenomena peculiar to the working of our brain in the face of rapidly developing modern technology. The treatment of this subject will furthermore be accompanied by several practical conclusions which will facilitate the organization of men's work along rational and hygienic lines in accordance with the findings of modern physiology.