PREFACE TO FOURTH EDITION. 



The preparation of a fourth edition of this Text Book of Physiology has 

 furnished the opportunity for revision and the incorporation of new matter. 

 Through condensation and elimination it has become possible to insert addi- 

 tional matter equivalent to some fifty pages without increasing the size of 

 the volume. The new paragraphs which have been inserted in the various 

 chapters contain facts relating to the mechanic movements of the stomach 

 and intestines and the nerve mechanisms regulating them; the digestion and 

 absorption of the proteins; the viscosity, specific gravity and coagulability 

 of the blood; the physiologic mechanism of the heart and the properties of 

 the cardiac muscle; the venous pulse; the auscultatory method of determin- 

 ing blood pressure; the modifications of the respiratory rhythm; the physio- 

 logic action of the pituitary gland and the adrenals, etc. These additions, 

 it is believed, will enhance its value to the medical student and practitioner. 



In the preparation of this, as of preceding editions the aim has been to 

 present the facts in a form that will familiarize students with the essential 

 problems of physiology. 



To those teachers and students who have recommended and used this 

 work and to whom I am indebted for generous praise, kind criticisms, and 

 helpful suggestions, I wish to express my sincere thanks and trust that in its 

 improved form it will continue to meet their approval. 



Once again I desire to express my appreciation of the unwearied and 

 invaluable assistance of Mr. I. A. Hagy in preparing the manuscript for the 

 press. 



I am also indebted to Dr. Lucius Tuttle, demonstrator of physiology, 

 for the reading of the proof. 



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