“The keeper became so worried over the kangaroo’s strange sickness that at night he would get up to see if the kangaroo was asleep. Every time he went to look, the kangaroo was sound, sound asleep, breathing very quietly. The keeper thought to himself that this must be a good sign, for if he happened to be suffering from indigestion he would certainly be moaning and having bad dreams. Finally the keeper decided the kangaroo must have heart failure.