He could differentiate the innumerable species of the herbivora by scent, and he could tell, too, whether an animal was approaching or departing merely by the waxing or waning strength of its effluvium.

他可以通过气味区分无数种类的食草动物，他也可以仅仅通过动物散发出的气味的强弱来判断动物是接近还是离开。