This book is intended for children. There is no subject in the presentation of which object-teaching may be employed with greater facility and profit than in teaching Physiology, and none which may be more advantageously impressed upon the student's mind by means of simple experimentation than the subject of Hygiene. Every teacher who uses this book is urgently requested to supplement each lesson by the use of object-teaching or experiments. A great number of simple experiments illustrative of both Physiology and Hygiene may be eadily arranged. Many little experiments are suggested in the text, which should invariably be made before the class, each member of which should also be encouraged to repeat them at home. It is also most desirable that the teacher should have the aid of suitable charts and models. In conclusion, the author would acknowledge his indebtedness for a large number of useful suggestions and criticisms to several medical friends and experienced teachers, and especially to Prof. Henry Sewall, of the University of Michigan, for criticisms of the portions of the work relating to Physiology.