ment, and manifold application of which is the material of all his works, even if written much later, can arise in him only up to the thirty-fifth or at the latest the fortieth year of his life, and are really the result of combinations he has made in his early youth. For they are not mere connections of abstract conceptions, but his own intuitive comprehension of the objective world and the nature of things. Now, that this intuitive apprehension must have completed its work by the age mentioned above depends partly on the fact that by that time the ectypes of all (Platonic) Ideas must have presented themselves to the man, and therefore cannot appear later with the strength of the first impression; partly on this, that the highest energy of brain activity is demanded for this quintessence of all knowledge, for this proof before the letter of the apprehension, and this highest energy of the brain is dependent on the freshness and flexibility of its fibres and the rapidity with which the arterial blood flows to the brain. But this again is at its strongest only as long as the arterial system has a decided predominance over the venous system, which begins to decline after the thirtieth year, until at last, after the forty-second year, the venous system obtains the upper hand, as Cabanis has admirably and instructively explained. Therefore the years between twenty and thirty and the first few years after thirty are for the intellect what May is for the trees; only then do the blossoms appear of which all the later fruits are the development. The world of perception has made its impression, and thereby laid the foundation of all the subsequent thoughts of the individual. He may by reflection make clearer what he has apprehended; he may yet acquire much knowledge as nourishment for the fruit which has once set; he may extend his views, correct his conceptions and judgments, it may be only through endless combinations that he becomes completely master of the materials he has gained; indeed he will generally produce his best works much later, as the greatest heat
