I had Apollo in the vets today, and as we're waiting for the vet I hear (yet another) person and dog go by. Nothing unusual about that, except THIS TIME Apollo whipped around, and started sniffing, and whining, and pawing at the door, and whining, and sniffing, and pawing at the door handle, and whining, and sniffing and drooling....and when we were done he put his nose down and tried to follow a scent right on out the door....
I didn't ask, but I figure its a fairly safe assumption they had a bitch in standing in heat through....he was kind enough to try marking at the exit door while we were waiting to pay the bill....