Buttercup the cat saved by blood transfusion from a dog

Who says that cats and dogs can't be friends?

When Buttercup the cat collapsed at his home in Key West, Florida, last month, a dog came to his rescue with a blood transfusion.

The tabby cat was diagnosed with anemia at the Marathon Veterinary Hospital after becoming lethargic. Healthy cats have a red blood cell count of at least 35 percent ... Buttercup's was just seven percent.

Doctors at the hospital told the cat's owner Ernie Saunders that the condition was life-threatening, but it would take too long to find a matching feline blood donor.

"It's a situation where you can't give type A blood to a type B blood cat because it'll cause a severe immune reaction ... Cat's blood is a little harder to come by and not as available as dog's blood," the cats vet, Dr. Sean Perry, told the Miami Herald.

That's where a dog comes into the picture and in this case, a greyhound. The hospital had packs of greyhound blood on hand from a blood bank, with red blood cells separated from the plasma.

Dr. Perry said that "Buttercup showed no signs of rejection" over the course of the four hour procedure called a xenotransfusion.

According to the National Library of Medicine, the procedure has been performed on 62 cats in the United States. A xenotransfusion can only be performed once because of antibodies in dog blood that cause a cat's immune system to react.

Saunders got another surprise during Buttercup's treatment: He learned during procedure that the cat is a male ... not a female, as he previously thought.

More from AOL
J.K. Rowling tweets cryptic riddle, sends fans into a frenzy
Professors plan to spend 73 days underwater, break world record
Jimmy Fallon and will.i.am make Ew! show music video