Rushing to the rescue…Hold on, Drollman, we’re coming! 
Actually, I thought that was kind of an interesting question, so I had to drop what I was doing (cruising the boards :rolleyes :), and go get MY copy and fast forward it to the part you’re talking about.
They’re coming out of the house after the people discover that Tramp was actually killing a rat in the baby’s room. Trusty says, “We’ll track him,” and Jock and Trusty set off. Trusty loses the scent, and Jock says sadly, “Let’s face it, man, you’ve lost your sense of smell.”
It’s not generally known, Drollman, but in the original print, immediately after Jock says this, Trusty actually growled, “Sk my big floppy donkey d*ck, you cks**king mrfr,” before he resumes tracking Tramp through the mud. However, before the movie was released, Uncle Walt realized that some people in the Bible Belt might take this line the wrong way, and had it deleted from the sound track, hence the lack of audio in those few frames.
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…and if you believe that, Drollman, I’ve got a bridge in Brooklyn that I might be able to get for you at a knockdown price… 
No, seriously, D, I went and looked at my tape. What’s happening there is that after Jock says, “Let’s face it, man, you’ve lost your sense of smell,” Trusty gives him, first, an incredulous look, and then gives his jowls a mighty shake, as if to say, “Just watch me!” and continues tracking Tramp through the mud. He doesn’t say anything at all–dramatically speaking, a dignified silence is a better answer to Jock’s skepticism than any protestations of “oh, yes, I can!”
Snopes has a section just for Disney. Check it out.
http://snopes.simplenet.com/
“Why, sometimes I’ve believed as many as six impossible things before breakfast!” - the White Queen