He cocked his ear--he heard a little wh-i-s-s-s-s-t. “What’s this,” he muttered, and grabbed another bottle and cracked off its neck, holding his ear close by. Wh-i-s-s-st! There it was again. “That means the air is coming out of my bottle, or going into it,” he cried, and he lighted a candle and ingeniously held it near the neck of a third flask as he cracked the seal. The flame sucked inward toward the opening. “The air’s going in--that means the air in the bottle is less elastic than the air outside, that means maybe Needham is right!” For a moment Spallanzani had a queer feeling at the pit of his stomach, his forehead was wet with nervous sweat, his world tottered around him.... Could that fool Needham have made a lucky stab, a clever guess about what heat did to air in sealed up flasks? Could this windbag knock out all of this careful finding of facts, which had taken so many years of hard work? For days Spallanzani went about troubled, and snapped at students to whom before he had been gentle, and tried to comfort himself by reciting Dante and Homer--and this only made him more grumpy. A relentless torturing imp pricked at him and this imp said: “Find out why the air rushes into your flasks when you break the seals--it may not have anything to do with elasticity.” The imp woke him up in the night, it made him get tangled up in his masses.... Then like a flash of lightning the explanation came to him and he hurried to his work bench--it was covered with broken flasks and abandoned bottles and its muddled disarray told his discouragement--he reached into a cupboard and took out one of his flasks. He was on the track, he would show Needham was wrong, and even before he had proved it he stretched himself with a heave of relief--so sure was he that the reason for the little whistling of air had come to him. He looked at the flasks, then smiled and said, “All the flasks that I have been using have fairly wide necks. When I seal them in the flame it takes a lot of heat to melt the glass till the neck is shut off--all that heat drives most of the air out of the bottle before it’s sealed up. No wonder the air rushes in when I crack the seal!”