What does the Bloodhound track when working a trail, rather than following the subject visually?

Answer

Scent molecules left behind, such as skin cells or sweat

The Bloodhound tracks the scent molecules left behind from skin cells, sweat, or disturbed earth, rather than following the visible path the person or animal took.

What does the Bloodhound track when working a trail, rather than following the subject visually?
ScentDogbreedingpurposeBloodhound