PREFACE TO THE FIRST EDITION ix 



John Waters, a student ol' nRnlieinc here. To their skill and care 

 I owe much. 



I am greatly obliged to Mr. A. V. Steen, B.Sc., one of om* 

 demonstrators, for reading all the proofs. The freedom of the 

 matter from certain errors is the result of his painstaking efforts. 



Finally, I desire to record my gratitude to my publishers for 

 their patience and courtesy during the prolonged period of publica- 

 tion and to the printers for the care they haAC taken and the con- 

 sideration shown when my ignorance made large demands on their 

 time and patience. 



Institute of Physiology, 



University of Glasgow. 



