why an untrained heart should not be overtaxed, with the work of the lymphatics and the nature of the exchanges made between lymph and plasma. The insidious effects of alcohol on the heart and on the entire circulatory system are emphasized.

Certain conditions of breathlessness are discussed, and reasons are given for the statement that a man runs as much with his heart and with his lungs as with his legs. In natural sequence, this explanation involves not merely the structure and the function of the lungs, but also a study of the exchange of gases both in the tissues and in the air sacs.

The notable experiments of Professor Chittenden with United States soldiers in New Haven, and of Dr. Cannon with cats in the Harvard Medical School, necessarily add a touch of picturesque reality to the otherwise prosaic subject of digestion. Through this introduction to the subject prominence is given to the change of food from solid to liquid form, and to its absorption by the villi; also to the food requirements of the body under differing conditions of age and activity; to the value of bulk in the food supply; to the functions of the liver and of the kidneys, and to the influence of alcohol in undermining their power for work; to the relation of sweat glands to bodily heat, and to the interdependence of work, heat, and fuel in the operations of the body.

In close connection with the physiology of the text, several chapters discuss communicable disease and its prevention. They study tuberculosis, its cause, how to avoid it, and how to cure it; also typhoid fever as related to pure water and clean milk; dangers from the common drinking cup and the common towel, from the fly, the mosquito, and unsanitary surroundings; also the cause of specific epidemics and ways of escape from them through vaccination, antitoxin, cleanliness, and general physical vigor.

The closing chapters of the book are devoted to the nervous system, to its structure and its function, to methods of governing it through mental processes, and to the training of the senses.

These and other related topics have been brought to the notice of the students of this volume with the hope of imparting such enthusiasm for personal health, and such clear notions of how to secure it, that the bodies of growing children may be strengthened as well as straightened, that lives may thereby be lengthened, and that through increased physical well-being the sum of human happiness may itself be increased.

Not merely is it the purpose of this series to teach scientific facts, but also, and especially, so to arrange and present these facts that from page to page they shall hold the reader's close attention and inspire personal loyalty to the laws of health. To further this purpose

side headings have intentionally been omitted, so that each chapter may make its first appeal to the reader as a unified whole rather than as a series of disjointed fragments. While the disadvantages of side headings in interrupting the continuity of thought have been avoided, all their advantages are secured through the questions at the end of the volume, which, in a better form, answer the same purpose.

In so far as possible, the instruction of this text-book is everywhere reënforced by illustrations. Special mention should be made of indebtedness to the American Journal of Physiology for illustrations used by Dr. Cannon in his article on "The Movements of the Stomach studied by Means of the Röntgen Rays" (1898), and to Professor Chittenden for photographs of the soldiers with whom he carried on his food experiments.

Other valuable illustrations have been reproduced from Practical Hygiene by Alice Ravenhill, from The Human Mechanism by Theodore Hough and W. T. Sedgwick, from Alcohol and the Human Body by Sir Victor Horsley and Mary D. Sturge, and from Unser Körper by F. A. Schmidt. To each of these and to many other important works this little book is indebted not merely for illustrations but also for valuable facts which have been used in the preparation of its subject

matter.

F. G. J.

THE BODY AND ITS DEFENSES

CHAPTER I

BONE AND MUSCLE RECORDS

Many cases are on record where a man has tried to hide his face when he thought his photograph was to be taken. He has seemed to understand that the photograph might betray him some day and lead to his being arrested again.

But some of our largest cities have adopted a new and surer way of keeping a reminder of their captured men. They measure each man carefully in different directions, height in standing and in sitting, distance from the outstretched finger tip of one hand to the outstretched finger tip of the other, length and width of head and face and right ear, length of left foot, of left middle finger, and of left forearm. Scars are noticed and recorded; also the color of the hair and eyes, the shape of the nose, the number of teeth, etc.

In addition, the photograph is taken. And, queer though it may seem, the photograph is less important than the measurements in identifying a man if he is

ever arrested again and brought to the police station. The reason is that our bone measurements change little after we are twenty-two years old. Ever after

that the size of face and head, the length of arms, of fingers, and of legs are all as they will continue to be until we die.

This, then, is a sure and sensible way of keeping the record of a man. When a criminal arrives at the police court, no matter how violently he declares that he has never been there before and that this is his first offense, the officers measure him at once and also search their written records. If they find there any set of measurements which is a duplicate of those just taken, all the man's denials are in vain. Those officers know that never yet have two people been found who had precisely the same dimensions for all the bones which were measured.

It takes but ten minutes for the officers to get their record of a man-photograph and all. But it took the