Sentence:  Nevertheless, since the <WSD>downface</WSD> is so desirable, some little extra credit should be given when it appears to perfection, because it is also one of the harder points to obtain in breeding, and the dog with it should go over the dog that has not got it, even if the second dog is better in body; yet the line of demarcation has to be carefully drawn, for if undue weight be attached to the <WSD>downface</WSD> there is the danger that it will be the insertion of the thin end of the wedge, and bodies will become somewhat neglected. 
Meaning of the word marked with <WSD> tags:  A profile characterized by a downward sloping muzzle.