PREFACE XV 



It is much to be regretted that these references are not more 

 nearly up to date; but publication has been delayed by various 

 unforeseeable causes, including the printing industry's national 

 dispute during 1959 and the writer's serious illness. 



Finally a word of explanation about some of the things which 

 have not been included in the book. Examples in which extracts 

 of one kind of animal have been tested upon another kind have 

 been avoided, on the grounds that they are apt to lead to unsound 

 physiological deductions. Details of standard techniques are 

 omitted, since the reader can refer to any physiological text- 

 book for an account of such methods as recording muscle con- 

 tractions by means of levers that mark a revolving smoked drum 

 (e.g. Figs. 3-1 and 3-3). The use of commercial hormone prepara- 

 tions and methods of quantitative estimation of hormones by 

 biological assay are also omitted, as being primarily of clinical 

 interest. Since the book is intended for zoologists and comparative 

 physiologists, the mammalian examples have been chosen from 

 species other than man, while reference to pathological and clinical 

 material has been omitted, as being outside their chosen field. 

 Such material is easily accessible elsewhere, and should not be 

 difficult to fit into the present framework, if the reader so desires. 



Bristol P. M. J. 



