[4] “Our material frame is composed of innumerable atoms, and each separate and individual atom has its birth, life, and death, and then its removal from the ‘place of the living.’ Thus there is going on a continuous process of decay and death among the individual atoms which make up each tissue. Each tissue preserves its vitality for a limited space only, is then separated from the tissue of which it has formed a part, and is resolved into its inorganic elements, to be in due course eliminated from the body by the organs of excretion.”—Maclaren’s _Physical Education_. [5] The periosteum is often of great practical importance to the surgeon. Instances are on record where bones have been removed, leaving the periosteum, within which the entire bone has grown again. The importance of this remarkable tissue is still farther illustrated by experiments upon the transplantation of this membrane in the different tissues of living animals, which has been followed by the formation of bone in these situations. Some years ago a famous surgeon in New York removed the whole lower jawbone from a young woman, leaving the periosteum and even retaining in position the teeth by a special apparatus. The entire jawbone grew again, and the teeth resumed their original places as it grew. [6] The mechanism of this remarkable effect is clearly shown by an experiment which the late Dr. Oliver Wendell Holmes used to take delight in performing in his anatomical lectures at the Harvard Medical College. He had a strong iron bar made into a ring of some eight inches in diameter, with a space left between the ends just large enough to be filled by an English walnut. The ring was then dropped to the floor so as to strike on the convexity just opposite to the walnut, which invariably was broken to pieces. [7] For the treatment of accidents and emergencies which may occur with reference to the bones, see Chapter XIII. [8] “Besides the danger connected with the use of alcoholic drinks which is common to them with other narcotic poisons, alcohol retards the growth of young cells and prevents their proper development. Now, the bodies of all animals are made up largely of cells, ... and the cells being the living part of the animal, it is especially important that they should not be injured or badly nourished while they are growing. So that alcohol in all its forms is particularly injurious to young persons, as it retards their growth, and stunts both body and mind. This is the theory of Dr. Lionel S. Beale, a celebrated microscopist and thinker, and is quite generally accepted.”—Dr. Roger S. Tracy, of the New York Board of Health.