"The study of Expression is difficult owing to the movements being often extremely slight and of a fleeting nature. A difference may be clearly perceived and yet it may be impossible at least I have found it so to state in what the difference consists. When we witness any deep emotion our sympathy is so strongly excited that close obser vation is forgotten or rendered almost impossible; of which fact I have had many curious proofs. Our imagination is another and still more serious source of error; for if from the nature of the circumstances we expect to see any expression we readily imagine its presence. Notwithstanding Dr. Duchenne's great experience he for a lon time fancied as he states that several muscles contracted under certain emotions whereas he ultimately convinced himself that the movement was confined to a single muscle."