The next time someone says, “I smell danger in the air,” that might literally be true — and the odor might be coming from you.

At the tip of the noses of mammals, including humans, is a ball of nerve cells known as the Grueneberg ganglion, named after Hans Grueneberg, the scientist who described the structure in mice in 1973.

Grueneberg thought it was just a nerve ending. Only in last few years, after scientists devised strains of mice that glow green under fluorescent light, did they deduce that the Grueneberg ganglion is a component of the olfactory system. But they still did not know what the ganglion smelled.

In the Aug. 22 issue of the journal Science, researchers at the University of Lausanne in Switzerland report that they have figured it out, at least for the green-glowing mice.

All sorts of organisms, including plants, insects and mammals, release “alarm pheromones” when they sense danger; the pheromones waft through the air to warn others. Very little is known about the alarm pheromones of mammals other than that they exist. Scientists have not identified the compounds; they do not know where in the body the pheromones are produced. Nonetheless, the Lausanne scientists could collect the pheromones by simply stressing mice and sucking up the air around them.

When other normal mice were exposed to the danger-scented air, they froze in their tracks. But mice whose Grueneberg ganglia had been excised did not notice anything wrong and continued to wander around their cages without a care in the world.

如果未來時候某人說：“我聞到空氣中的危險”，那可能確實是真實的——這氣味或許就是從你而來。

在哺乳動物包括人類的鼻端，有一個稱之為格呂內貝格神經節的神經細胞球，是科學家漢斯 格呂內貝格在 1973 年描述了小鼠體內的這種結構之后命名的。

格呂內貝格認為這只是一個神經末梢。僅僅在最近幾年，在科學家們發明了在熒光燈下發出綠色輝光的小鼠品系之后，他們推斷，格呂內貝格神經節是嗅覺系統的一個組成部分。但是他們仍然不知道這個神經節所嗅的是什么東西。

在 8 月 22 日出版的《科學》雜志中，瑞士洛桑大學的研究人員報告說，他們已經將這個神經節圖示出來，至少是對于綠色輝光的小鼠。

各種生物體，包括植物、昆蟲和哺乳動物，都在它們意識到危險的時候釋放出“報警信息素”；這種信息素通過空氣飄出，以警示其它的伙伴。對于哺乳動物的報警信息素，除了它們的存在之外，所知非常之少。科學家尚未鑒別出該種化合物；他們也不知道信息素在在機體內的什么地方產生。然而，洛桑的科學家們能夠通過對小鼠簡單地增加壓力并且吸取牠們周圍的空氣來收集信息素。

當其它正常的小鼠暴露于危險氣味的空氣中時，牠們立即在牠們的行蹤上停止不動。而切除格呂內貝格神經節的小鼠則沒有注意到任何不對的情況，并且繼續在牠們的籠子中無憂慮地在這個世界中徘徊游蕩。