82 IMMUNITY 



conjunctiva can this reaction be obtained. These skin tests are called the von 

 Pirquet's cutaneous or Moro's percutaneous tests. 



Syphilis. The poison of the Treponema pallidum is called luetin. It is 

 made by grinding up in salt solution a culture of the germ, heating the resulting 

 mass to 60 C. for an hour and preserving it with phenol. If this be instilled 

 into an abraded skin area a maculopapule or nodular eruption occurs in a 

 syphilitic. This positive outcome, however, only appears in late cases, those 

 of tertiary stages and in treated cases. It therefore complements the 

 Wassermann reaction, being positive where this is apt to fail. 



Carriers. After recovery from certain diseases, notably typhoid fever, diph- 

 theria and cholera, convalescents may carry in themselves fully virulent germs 

 with no outward evidences thereof. Such persons are called "carriers" and 

 are of the highest importance in hygiene. The reasons for this condition are 

 several. These germs may be removed from the bodily defenses or the body 

 may be immune to them; again they may be fixed or fast strains. Wherever 

 they are they may escape and infect another person. After typhoid fever 

 bacilli remain, in the gall passages and bladder; after cholera in the deep 

 mucous membranes and after diphtheria the crypts of the tonsils or the naso- 

 pharynx may hold them. Vaccination or operation may be needed to remove 

 them. Persons never known to have had enteric fever have been known to 

 harbor bacilli in their gall bladder. One typhoid carrier, "Typhoid Mary" a 

 cook, is known to have infected 26 persons. 



