From the ArcaMax Publishing, Cats & Dogs Newsletter:
http://www.arcamax.com/news/catsanddogs/s-185293-378183
Secretariat, AKA "Big Red", dominated thoroughbred racing in the 1970s
and is considered by many to be the greatest racehorse ever. Big Red
won the coveted Triple Crown in 1973. W
hen Secretariat won the Kentucky Derby, he did so while accomplishing
a feat never seen before -- "negative splitting." Secretariat ran each
quarter-mile segment faster than the one before. Secretariat's winning
time would have won any Kentucky Derby before or since (Source:
Wikipedia.org). Secretariat died October 4, 1989.
Before his burial, a necropsy revealed that Secretariat had a heart
approximately twice the size of a normal horse's heart -- the largest
the experienced veterinarian had ever seen in a horse.