The powers of living matter are still more characteristic. It is continually wasting away by a kind of internal combustion, but continually repairs the waste by the processes of growth. Moreover, this growth is of a characteristic kind, differing absolutely from the so-called growth of lifeless things. Crystals and other lifeless bodies grow, if at all, by accretion, or the addition of new particles to the outside. Living matter grows from within by intus-susception, or taking in new particles, and fitting them into the interstices between those already present, throughout the whole mass. And, lastly, living matter not only thus repairs its own waste, but also gives rise by reproduction to new masses of living matter which become detached from the parent mass and enter forthwith upon an independent existence. Scope of Biology: "Biology has already been defined as the science which treats of matter in the living state. Whatever pertains to living matter or to living things pertains to biology. The study of the forms of living things, of their habits, actions, nutrition, surroundings, distribution; of their relations to the lifeless world, and to one another.