PREFACE 



in making the photographs from which the 

 drawings for the illustrations in the chapter 

 on Post-Mortem Examinations were pre- 

 pared. Much valuable information has 

 also been obtained from bulletins issued by 

 the experiment stations of the United States 

 and by the Ontario Agricultural College of 

 Canada. 



E. J. WORTLEY. 



Vll 



