The facts brought to light by my electrophysiological research on the mechanism of human facial expression are of considerable importance; they are, in general, so unexpected or in opposition to certain prejudices and to general opinion that experimental demonstration is the only way to make them acceptable to science.

Photography, as true as a mirror, can illustrate my electrophysiological experiments and help to judge the value of the deductions that I have made from them.

From 1852, convinced of the impossibility of popularizing or even of publishing this research without the aid of photography, I approached some talented and artistic photographers. These first trials were not, and could not be, successful. In photography, as in painting or sculpture, you can only transmit well what you perceive well. Art does not rely only on technical skills. For my research, it was necessary to know how to put each expressive line into relief by a skillful play of light. This skill was beyond the most dextrous artist; he did not understand the physiological facts I was trying to demonstrate.

Thus I needed to initiate myself into the art of photography.

I photographed most of the 73 plates that make up the Scientific Section of this Album myself, or presided over their execution, and so that none shall doubt the facts presented here, I have made sure that not one of the photographs has been retouched.