That opinion on the value of bacterial antigens in the prophylaxis of whooping cough is conflicting is generally admitted. A similar state exists concerning the value of convalescent blood, but the use of this method has not been sufficiently adequate to obtain proper evidence for conclusions. In general, convalescent serum has proved to be more valuable in the prevention of those diseases in which the etiologic agents are filtrable viruses. Although it is not assumed that a virus causes whooping cough, it seems reasonable to suggest that it has not been entirely ruled out and that one may consider the cause to be a possible combination of virus and bacteria, such as Shope1 showed to be the cause of swine influenza. Certain evidence presented particularly by McCordock2 and by Rich3 is so suggestive that it seems worth while to record a summary of the literature concerning the