“It is old age which is come upon me,” he cried; “I feel painful impressions much less acutely and pleasant impressions have less effect on me. The relative proportions of the two remain as before, that is to say, unpleasant things still impress me much more strongly than pleasant things.” By analysing and comparing his emotions, he discovered something new, in fact that some impressions were, so to speak, neutral. As he was less sensitive to unharmonious sounds, and at the same time less affected by music itself, he found himself in a more tranquil condition. Awakening in the middle of the night, he experienced a kind of happiness which reminded him of that formerly produced by morphine, and which was characterised by his hearing no sound, either pleasant or unpleasant. He became less disgusted by drugs, but at the same time indifferent to the pleasures of the table which he had appreciated in his youth. He also delighted in consuming more and more simple food. A piece of black bread and a glass of water became real treats to him. Insipid dishes, which he formerly despised, were now specially agreeable to him. Just as in the evolution of art, violent coloration has yielded to the low tones of Puvis de Chavannes, as views of fields and meadows are preferred to those of mountains and lakes; just as in literature, tragic and romantic studies have been successfully replaced by scenes of daily life, so the psychical development of my friend displayed a similar change. Instead of taking his pleasure in mountains or in places famed for their picturesqueness, he was content to watch the budding of the leaves of the trees of his garden, or a snail overcoming its fears and putting out its horns. The simplest occurrences, such as the lisping or the smile of a baby or the first words of a child, became sources of real delight to this elderly man of science. What was the meaning of these changes which took so many years to be accomplished? It was the growth of his sense of life. The instinct of life is little developed in youth. Just as a young woman gets more pain than pleasure from the earlier part of her married life, just as a new-born baby cries, so the impressions from life, especially when they are very keenly felt, bring more pain than pleasure during a long period of human life. The sensations and feelings are not stable; they undergo evolution, and when that takes place more or less normally, it brings about a state of psychical equilibrium. And thus my friend, formerly so entrenched in pessimism, came to share my optimistic view of life. The discussions that we had had for so many years ended in complete agreement. “However,” said he, “to understand the value of life, one must have lived long; otherwise one is in the position of a man blind from his birth to whom are recounted the beauties of colours.” In a word, my friend towards the end of his life changed from abject pessimism to complete optimism.