The Academy of Sciences, which shows by the rarity of its reports the importance which it attaches to them, gave for the second time an account of these new researches. M. Biot was again the reporter. It was with a sort of coquetry that Pasteur brought from Strasburg perfectly labelled specimens of the magnificent crystallisations of the double series of right-handed and left-handed tartrates. By means of models he was able to render the forms of these crystals visible at a distance. M. Biot undertook to bring the subject before the Academy. On the morning of the day when he was to read his report he spent several hours in conversation with Pasteur. M. Biot became so excited during the discussion that Madame Biot, with the solicitude peculiar to the wives of Academicians, requested Pasteur to change the subject of conversation. The members of the Academy shared the enthusiasm of M. Biot. Arago moved that the report be inserted in the collected _mémoires_ of the Academy. This was an exceptional honour. Arrived for the most part at the end of their own careers, these learned men observed with pleasure the incipient ray which had not yet become a glory but which was the precursor thereof. * * * * * 'My young friend,' said M. Biot to Pasteur, when presenting him to Mitscherlich somewhere about that time, 'you may boast of having done something great, in having discovered what had escaped such a man as this.' 'I had studied,' replied Mitscherlich, not without a shade of regret, addressing himself to Pasteur, 'I had studied with so much care and perseverance, in their smallest details, the two salts which formed the subject of my note to the Academy, that, if you have established what I was unable to discover, you must have been guided to your result by a preconceived idea.' Mitscherlich was right, and this preconceived idea might have been formulised thus: A dissymmetry in the internal molecular arrangement of a chemical substance ought to manifest itself in all its external properties which are themselves capable of dissymmetry. * * * * *