bloodhound. Someone (or perhaps something) who tracks down people.
Real bloodhounds are associated with tracking criminals, and indeed you will find this usage, especially in crime fiction. However, it comes in for more general categorization as well. Maureen Dowd describes the White House switchboard operators as “bloodhounds” who could “get Santa on the line” for Caroline Kennedy, back in the day.
There is good reason for this usage. Dogs do have an impressive capacity to distinguish smells, with the ability to differentiate odor with more subtlety than humans bring to vision. A dog's nasal membranes have about 220 million smell receptors, while a human has a measly 20 million. Not only can they identify scents which are days or weeks old, separating them from the welter of other smells, they can figure out in which direction a “suspect” is traveling by distinguishing the minute differences in the age of each scent imprint. Famed hound Nick Carter (a dog not a human) is credited with finding more than 650 criminals and following one trail that was over 4 days old. Dogs are not alone in these capacities; all of the canids have comparable olfactory systems. Nor do dogs especially care about catching criminals or the smell of illegal drugs or explosives. What makes them excellent at tracking elusive human beings is that dogs want to please their human companions and will track without attacking the prey when they find it, unlike wolves or jackals. There are some peculiarities about the ways dogs develop that account for this difference. That, however, is another story.
The Bristol Bloodhound was a British surface-to-air anti-aircraft missile used by the RAF during the later part of the 1950s. The Bristol Bloodhound was powered by Thor-type ramjets, which produced a flight speed in excess of mach 1(the speed of sound). I guess it “sniffed out” the target. Unlike a dog, however, the humans who sent it out to do their bidding intended for it to attack and kill the prey it found.
1. Dowd, Maureen. 2007. A Tale of Trigger. New York Times, Dec 26, A27.
2. Angier, Natalie. 2008. The Nose, and Emotional Time Machine. New York Times, Aug 5, D1, 4.
3. Budiansky, Stephen. 2001. The Truth About Dogs. New York: Penguin Books, 118-123.
4. Wikipedia contributors. 2008. Bloodhound. Wikipedia. Wikimedia Foundation. Accessed Aug 10 2008 from http://en.wikipedia.org/wiki/Bloodhound.
5. Probert, S V E. Probert Encyclopaedia. Probert: 1993-. Accessed Apr 18 2002 from http:// www.probertencyclopaedia.com/.