“Not to dwell on the natural pain, the gloom, and the waste of time and money thus entailed, only consider how greatly ill health hinders the discharge of all duties,—­makes business often impossible, and always more difficult; produces irritability fatal to the right management of children, puts the functions of citizenship out of the question, and makes amusement a bore.  Is it not clear that the physical sins—­partly our ancestors’ and partly our own—­which produce this ill health deduct more from complete living than anything else, and to a great extent make life a failure and a burden, instead of a benefaction and a pleasure?”—­Herbert Spencer.

[2] The word protoplasm must not be misunderstood to mean a substance of a definite chemical nature, or of an invariable morphological structure; it is applied to any part of a cell which shows the properties of life, and is therefore only a convenient abbreviation for the phrase “mass of living matter.”

[3] “Did we possess some optic aid which should overcome the grossness of our vision, so that we might watch the dance of atoms in the double process of making and unmaking in the living body, we should see the commonplace, lifeless things which are brought by the blood, and which we call food, caught up into and made part of the molecular whorls of the living muscle, linked together for a while in the intricate figures of the dance of life, giving and taking energy as they dance, and then we should see how, loosing hands, they slipped back into the blood as dead, inert, used-up matter.”—­Michael Foster, Professor of Physiology in the University of Cambridge, England.

[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.