ANIMAL DENTISTRY. 



145 



leaving the fissure oris free from obstruction. They have 

 the advantage also of opening the mouth to any width de- 



Fic. loi. 



sired, and the disadvantages of being none too reliable. The 

 ratchet may break or slip when the jaws of a powerful horse 



Fig. 102. 



are set against its strength. Slipping of the ratchet is a very 

 frequent accident after the catches have become worn from 

 constant use. 



