 In 1850, Davaine along with French pathologist Pierre François Olive Rayer, discovered a certain microorganism in the blood of diseased and dying sheep.In the diseased blood, Rayer and Davaine observed the bacillus that is known today as "Bacillus anthracis", the causative bacterium of anthrax.Soon afterwards, Rayer published a description of the bacillus in a paper titled, "Inoculation du sang de rate" (1850).