This satellite image taken Thursday shows the oil slick in the Gulf of Mexico as it nears the shoreline, threatening wildlife along Louisiana's fragile islands and barrier marshes. NASA/AP hide caption

itoggle caption NASA/AP

Veterinarian Diane Febles (left) and her assistant, Tracey McKnight, of Veterinary Equine Dentistry work on a horse in Henry County, Ga. The silver speculum keeps the horse's mouth open and prevents the animal from biting Febles' fingers. Joanne Silberner/NPR hide caption

itoggle caption Joanne Silberner/NPR