He was not happy with that because he could not run as fast as other animals and could not jump as far or as high as others who had four legs. So, he went up to the Great Indra's heaven to ask for his fourth leg.
"Oh, Great Indra, please give me the fourth leg like you did to other animals," asked the dog.
The Great Indra said, "Well, there is no leg left. I have given them all away to the other animals that came earlier. You are too late, Dog."
"Oh, please, Great Indra, please give it to me. If I don't get my fourth leg, I won't go down to earth," said the determined dog.
"I don't have any more leg to give you. I have given all legs away. All I have now are the legs of my stool. Well, since you insist, why don't you take one of the legs of my stool," suggested Indra.
"Oh, thanks so much Great Indra. Now I can jump as high or as far as others and I can run as fast as them too," said the dog.
"Now that you have the leg of my stool, Dog, you must promise to keep it as clean as possible. Don't you ever soil it in anyway," commanded Indra.
"Yes, Sire," confirmed the dog. "Even when I urinate, I will lift my fourth leg up to keep it clean."
* * *
I found this tale here.