As an instance of the way in which dangers may work in unsuspected ways, I may mention the fact that Emmerich, in examining the soil beneath a ward of a hospital at Amberg, discovered therein the peculiar bacillus which causes pneumonia, and which had probably been the cause of an outbreak of pneumonia that had occurred in that very ward.

She could see, as he saw, the "beauty" of the long trains of research by which Sir Martin Crozier had tracked down the bacillus of amoebic dysentery and established the difference between typhoid and Malta fever.