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.

如果未来时候某人说：“我闻到空气中的危险”，那可能确实是真实的——这气味或许就是从你而来。

在哺乳动物包括人类的鼻端，有一个称之为格吕内贝格神经节的神经细胞球，是科学家汉斯 格吕内贝格在 1973 年描述了小鼠体内的这种结构之后命名的。

格吕内贝格认为这只是一个神经末梢。仅仅在最近几年，在科学家们发明了在荧光灯下发出绿色辉光的小鼠品系之后，他们推断，格吕内贝格神经节是嗅觉系统的一个组成部分。但是他们仍然不知道这个神经节所嗅的是什么东西。

在 8 月 22 日出版的《科学》杂志中，瑞士洛桑大学的研究人员报告说，他们已经将这个神经节图示出来，至少是对于绿色辉光的小鼠。

各种生物体，包括植物、昆虫和哺乳动物，都在它们意识到危险的时候释放出“报警信息素”；这种信息素通过空气飘出，以警示其它的伙伴。对于哺乳动物的报警信息素，除了它们的存在之外，所知非常之少。科学家尚未鉴别出该种化合物；他们也不知道信息素在在机体内的什么地方产生。然而，洛桑的科学家们能够通过对小鼠简单地增加压力并且吸取牠们周围的空气来收集信息素。

当其它正常的小鼠暴露于危险气味的空气中时，牠们立即在牠们的行踪上停止不动。而切除格吕内贝格神经节的小鼠则没有注意到任何不对的情况，并且继续在牠们的笼子中无忧虑地在这个世界中徘徊游荡。