PREFACE TO THE FOURTH EDITION 



It is nearly twenty years since the first edition of this work was 

 published. In consequence of a fourth edition being called for, 

 an endeavour has been made to deal with the subject on a some- 

 what wider basis than previously, and this has necessitated the 

 book being rewritten and enlarged. 



The work is essentially a veterinary, and not a com- 

 parative, physiology. It treats of physiology not only from 

 its theoretical aspect, but from the point of view of clinical 

 utility. The requirements of the student and practitioner have 

 consequently not been lost sight of, and every opportunity has 

 been taken in the text to point out the clinical application of 

 physiological facts. To several chapters a special appendix is 

 added, in order to enforce the lesson that pathology is only 

 physiology out of health. 



As in the last editions, so also in this, I have derived much help 

 from the well-known English Textbooks on Human Physiology, 

 and wish to express my special indebtedness to the similar 

 works of Professor Howell of Baltimore, and Professor Stewart 

 of Cleveland. 



The authorities and observers whose work has assisted in the 

 preparation of various chapters are acknowledged in the text, or 

 included in the list of authorities to be found at the end of the 

 volume. 



Numerous references have been made to the monumental 

 Trait e de Physiologie Comparee des Animaux, by the late Pro- 

 fessor G. Colin, of the Veterinary School of Paris. He was the 

 father of veterinary physiology, and though his treatise was 

 published over forty years ago, his experimental work will last 

 for all time. 



