According to the AKC standard for the breed, larger dogs are preferred by conformation judges. A common misconception is that Bloodhounds are employed in packs; while this is sometimes the case in Britain, where foxhound blood is mixed into them to increase speed, in North America, Bloodhounds are used as solitary trackers. When they are on a trail, they are usually silent and do not give voice as other scent-hounds. The original use of the Bloodhound as a leash-hound, to find but not disturb animals, would require silent trailing. Hunting the Clean Boot. ISBN 0-7137-0950-2.