In order to appreciate the extent of the defect of vision during emotion, I made the following experiment, together with Dr. Falchi. We took a small sample of writing from Snell’s tables, and then determined what was the greatest distance at which it could be easily read by a certain person; then, on some pretext, we scolded or reproached the subject in such a manner as to occasion a sudden and strong emotion. When we then requested the same person to read the writing, he was no longer able to do so at the same distance, but had to approach the tablet, often by a few steps, in order to see as before. A violent muscular exertion, a few turns on the trapeze or in the gymnastic rings, a race, the rapid ascent of a staircase, also diminish the acuteness of vision in a noticeable manner. III When one considers as a whole the symptoms by which fear reveals itself, one might almost think that it was a product of heredity and selection. Animals that are easily frightened, a disciple of Darwin would say, are those which can more easily avoid danger and save themselves; these produce young, and perpetuate their timidity in their posterity. But we know that the phenomena of fear are the morbid exaggeration of physiological facts. Animals cannot become continually more timorous by means of hereditary transmission; the necessity of struggling brings other faculties than those of flight and fear into play, and effect the preservation of the species in another way. Our organism is not such a perfect machine as to be able to resist or adapt itself to all conditions of environment; there are inevitable necessities against which selection is of no avail. In my opinion, although we may accept the principle of Spencer and Darwin as an explanation of many things, we yet cannot extend it to all phenomena. Spencer and Darwin were not physiologists enough; in their studies of the emotions they did not sufficiently seek the causes of the phenomena observed by them in the functions of the organism. There are, so to speak, hierarchies in the parts composing our machine, for all functions are not equally important. But in the whole of the vital economy one notices the preponderance and supremacy of the blood-vessels. It is so indispensable that the organism should profit by all the material procurable for the nutrition of the nerve-centres, that the circulation of the blood in all parts (therefore in the eye also) is subordinated to this prime object. In this way it seems to me the fact may be explained that the blood-vessels of the iris contract during strong emotions, notwithstanding that this produces excessive dilatation of the pupil, and that the back of the eye becomes anæmic, although this contraction of the vessels of the retina is disadvantageous to distinct vision.