412 INFECTION AND IMMUNITY. 



nated with earth appear to favor the development 

 of tetanus. This may be explained to some extent 

 by their ability to increase the virulence of the 

 tetanus bacillus, a condition which is noted in cul- 

 tures. In the wound they may engage the leuco- 

 cytes in phagocytosis and prevent ingestion of the 

 tetanus bacilli. As aerobic organisms they may 

 facilitate development of the bacilli by consuming 

 local oxygen. 



Our great harvest of tetanus following Fourth- 

 of-July injuries is closely associated in the first 

 place with the warm, dry season in which the 

 bacilli are more readily disseminated with dust, 

 and in the second place with the nature of the 

 wound and mixed infections, as described above. 



Occasionally tetanus follows the simplest 

 wounds, which may have healed entirely before 

 symptoms develop. In "idiopathie tetanus" and 

 in the so-called "'tetanus rheumaticus," which fol- 

 lows exposure to cold, the infection atria are un- 

 known. In the latter instance a latent infection, 

 whicn is stirred into activity by the reduction of 

 resistance which often follows exposure, may be 

 present; avirulent tetanus bacilli (?) were culti- 

 vated from the lungs of one such patient. The oc- 

 casional occurrence of tetanus following diphthe- 

 ria and typhoid suggests that infection may take 

 place through wounds of mucous surfaces. Neither 

 the bacillus nor its toxins penetrate the unbroken 

 skin or mucous membranes, and the alimentary 

 tract is further protected by the ability of the gas- 

 tric and pancreatic juices to digest the toxin. 

 period of The incubation period varies from two or three 

 incubation. dayg to several wee ^ j n t he statistics of Rose 20 



per cent, of the cases showed symptoms in the first 



