[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.

[9] “In its action on the system nicotine is one of the most powerful poisons known.  A drop of it in a concentrated form was found sufficient to kill a dog, and small birds perished at the approach of a tube containing it.”—­Wood’s Materia Medica.

“Tobacco appears to chiefly affect the heart and brain, and I have therefore placed it among cerebral and cardiac poisons.”—­Taylor’s Treatise on Poisons.

[10] “Certain events occur in the brain; these give rise to other events, to changes which travel along certain bundles of fibers called nerves, and so reach certain muscles.  Arrived at the muscles, these changes in the nerves, which physiologists call nervous impulses, induce changes in the muscles, by virtue of which these shorten contract, bring their ends together, and so, working upon bony levers, bend the arm or hand, or lift the weight.”—­Professor Michael Foster.

[11] The synovial membranes are almost identical in structure with serous membranes (page 176), but the secretion is thicker and more like the white of egg.

[12] “Smoking among students or men training for contests is a mistake.  It not only affects the wind, but relaxes the nerves in a way to make them less vigorous for the coming contest.  It shows its results at once, and when the athlete is trying to do his best to win he will do well to avoid it.”  Joseph Hamblen Sears, Harvard Coach, and Ex-Captain of the Harvard Football Team, Article in In Sickness and in Health.