IV STUDIES IN ADVANCED PHYSIOLOGY. 



There are in physiology, as, possibly, in all other 

 sciences, many problems at present which admit of different 

 interpretations, and which must be referred to the investi- 

 gations of the future for their correctness or their faultiness. 

 It would not be treating the reader right to shower him 

 with all sides of these questions, but the author has endeav- 

 ored to present that view in each case which seems most 

 generally accepted by scientific men, and awaiting future 

 verifications to show the value of the claim. By taking 

 this median course it is believed that the book will give to 

 its readers all of the main known facts, and in addition 

 acquaint them with many of those questions which are now 

 demanding the attention of physiologists. This will put 

 the science of physiology in its true light, it will show that 

 it is a living science, still at work trying to interpret living 

 problems. While it will show the present limitations of 

 our knowledge it will suggest future possibilities. 



It is hoped that the study of this book may result in a 

 more lively appreciation of physiological phenomena, and 

 an added interest in teaching the subject in our common 

 schools. 



It has been the aim to choose the illustrations for this 

 book with the greatest possible care. They have been 

 selected from quite a number of sources, and the proper 

 credit has in each case been given with every figure. Quite 

 a number of the histological illustrations are from Schafer's 

 Essentials of Histology. The author desires hereby to 

 thank Messrs. L,ongmans, Green & Company, the publish- 

 ers of that prince of text-books, Quain's Anatomy, for their 

 permission to reproduce several of the illustrations found 

 therein. The colored plates on the circulation of the blood 

 have been made possible by their courtesy. The author is 

 also under many obligations to D. Appleton & Company, 

 publishers of Osier's Practice of Medicine, for permission 

 to reproduce the colored plates illustrative of the nervous 



Louis J. RETTGER. 

 Terre Haute, Indiana, 

 Aug. 12, 1898. 



