We know as a universal rule that where there is rest there must be a balance of forces. If the ovum, the accumulator of the balanced forces in a state of rest, is to divide itself so as to produce in this way the future individual, some stimulant impulse, some energy is absolutely necessary to disturb the balance of forces, and to induce the development of the cells. This impulse may be such a one as occasions destruction. But it may also be one that gives occasion to new growth, to tissue formation. (W. Haacke.) We must describe this impulse as functional, and recognize in it a peculiarity which belongs to the organic world alone, the vegetable and animal kingdom. Every movement, every use of an organ, may serve as a stimulant impulse, and contribute to its development. Thus we find, in the case of great thinkers and poets, of celebrated generals, etc., a powerfully developed brain. Oarsmen, gymnasts, and swimmers have far stronger muscles than men who follow less fatiguing callings. In all these cases there are impulses leading to increased growth of the organs. In the growth of the fertilized ovum we have to deal again with a phenomenon of impulse, a part of which is the property of the ovum itself, a part, however, also dependent upon external influences. We call the former autoplastic, the latter xenoplastic impulse. (Haacke.) It is easy to understand that a purely autoplastic development (_eine reine Autoplasie_, a pure autoplasia) cannot exist. Out of an ovum alone, without the agency of new impulses, without the taking up of new matter, no new individual could develop. * * * * * The stomach furnishes the gastric juice. It is stimulated to do so by the food. The food is digested, undergoes absorption in the intestine, and becomes lymph. Blood is formed. The blood passes through the several organs and tissues, nourishes them, and replaces the substances used up by work. As soon, therefore, as the stomach and intestine, with the intestinal glands, fail in their functions, all the organs, which stand in physical relation with them, suffer; because they are constantly during their work consuming matter, and are now receiving no fresh supplies. The case of the other juices of the body is the same. The thyroid glands supply the body with a principle without which a person cannot be in a normal condition. Similarly the testicles, as glands, supply the body with a principle the want of which gives a man distinctly female qualities, as we perceive in the case of eunuchs. * * * * *