It was at first impossible for any one to realize what had actually happened. The smoke and fumes hid everything from sight, and
hundreds of men were thrown into a comatose or dying condition, and within an hour the whole position had to be abandoned, together with about fifty guns. —British Field Marshal Sir John French, report on the second battle of Ypres, 1915 What caused the scene described in this excerpt?
illnesses that reasulte frome the infection,presence and grouth of pathogenic (capable of causing disease)biotic agents in an individual human or other animal host.
