AUTHOR'S PREFACE ix 



regarding the building-up of a new animate system as a proper 

 field for physiological inquiry. 



On the other hand, I do not regard the terms '' experi- 

 mental " and " quantitative " in the sense employed above 

 as co-extensive. For this reason no reference is made in the 

 last chapter to the large body of work on implantation of 

 organs and regeneration, much of which is of great importance, 

 but like the too familiar descriptions of tracts in the mammalian 

 spinal cord, not susceptible as yet to treatment in relation to 

 the fruits of inquiries based on the use of physiological methods 

 as ordinarily understood. 



Generally speaking, I have borne in mind the fact that 

 Winterstein's Handbuch makes the literature of comparative 

 physiology accessible to those who care to consult it up to 191 2. 

 I have therefore aimed at familiarising the reader with what 

 has been done during the last ten or fifteen years. Where 

 references cannot be obtained by consulting monographs, the 

 particulars of the journals in which they are found are given. 

 The completeness of Winterstein's bibliography makes any 

 attempt to give further assistance to the student a work of 

 supererogation. 



In the selection of materials, one is naturally expressing 

 one's individual judgment ; and it is hoped that the reader 

 will appreciate that the author puts forward no claim to be 

 authoritative or encyclopaedic. The material selected has been 

 chosen to help the student of zoology to appreciate what is being 

 achieved by the application of physiological methods to the 

 study of the lower animals, and to widen the horizon of the 

 student of physiology who has not been brought into touch with 

 the diversity of problems which are suggested by a considera- 

 tion of function in a wider range of animals than those with 

 which he has been accustomed to deal in the course of his 

 medical studies. 



My thanks are due to Dr. A. D. Macdonald and Mr. A. D. 

 Hobson, who read the MS., and to Professor Julian Huxley foe 

 valuable suggestions. 



LANCELOT T. HOGBEN. 



March i, 1925. 



