Lecture IV

And now we reach the life period in which we must form our own third body (the fourth when counted from an external view), the time from puberty to the beginning of the twenties. The division of time in the later years is no longer so exact as the time between change of teeth and puberty. Now there is always more physical substance remaining behind; it stays fixed in the human being, it becomes permanent structure. Gradually a great deal of permanent structure accumulates. The older a person becomes, the less material is stripped away from the bones and replaced. Also in the rest of the organism certain parts need a longer time to separate off. And one can see a simple fact in connection with the teeth: that once one has got one's second set of teeth, whether one still has them later depends upon how long they last—just as with a knife, one only has it as long as it lasts. The knife can't renew itself. Teeth can't renew themselves either, really.