PREFACE TO THE FOURTH EDITION 



The operation for the surgical relief of roaring in horses, 

 iutroduced and developed by the author with the collab- 

 oration of Dr. Frost in 1905, and soon adopted as the 

 standard throughout the world, has continued to engage 

 our attention and every effort has been made to keep the 

 technic thoroughly up to date, 



Generally but one method of operating is described, the 

 one chosen being that which in the author's experience has 

 proven the most valuable in actual practice. No operation 

 has been introduced purely for practice but each one has 

 been tested and known to have practical value. 



When two methods of operating are given, they are in- 

 serted because each has definite points of superiority over 

 the other. One method may be specially applicable in a 

 given case, another in a different patient where the same 

 operation is to be performed. For example, a milk cow is 

 best spayed through the vagina while a heifer must be 

 operated upon by an incision through the abdominal walls. 



Considerable stress has been laid upon the surgical 

 anatomy of the parts involved in each operation ; some uses 

 of the various operations are mentioned ; some of the chief 

 dangers of each are pointed out and in some cases refer- 

 ences to literature upon the operation of the diseases for 

 which the operation is designed, are cited. 



Figures 14, 15, 17, 23, 29, 35, 39, 40, 49, 50, 

 53. 54. 55. 57. 60, 61, 64-68 are from Dr. Pfeiffer's 

 Operations-CursHs ; and the remaining plates and figuers 

 were either drawn under the direction of the author or 

 were made from original photographs. 



W. L. Williams. 



Cornell University, Sept., igig. 



