THE SPIROCHETE GROUP 399 



ance of the primary lesions. The organism then apparently 

 invades the blood stream and causes the lesions of secondary 

 syphilis. These usually appear as localized eruptions, fall- 

 ing of the hair and symptoms of generalized infection, such 

 as fever. The length of time which the secondary symptoms 

 may last is variable and depends upon the individual 

 infected. The disease may persist in latent or chronic form 

 throughout life of an individual. It leads to a great variety 

 of disorders, such as paresis (softening of the brain), de- 

 generation and production of tumors in the liver and other 

 organs of the body, diseases of the bones and of the blood 

 vessels. 



The disease is so important, so difficult to cure except by 

 the most careful and painstaking of medical treatment 

 extending over a period of years, that much .study has been 

 devoted to it. It is most frequently recognized in indi- 

 viduals not showing the active symptoms of the disease by 

 the use of the complement fixation reaction or Wassermann 

 test. Methods of satisfactorily immunizing against the 

 disease have not been developed. 



Syphilis is one of the most dreaded and loathsome of 

 diseases. It is most frequently transmitted by coition, 

 rarely through infected drinking vessels, toilets and by 

 direct inoculation as in surgical work. The disease may 

 be transmitted from mother to child, possibly even to the 

 third generation. 



LEPTOSPIRA ICTEROIDES 



It is probable that this organism is the specific cause of 

 the disease yellow fever in man. 



This disease is one of the most important of the tropical 

 plagues of man and has during the warm season frequently 

 invaded the temperate zone, particularly the Mississippi 

 valley in the United States. 



The organism is a slender, irregular spiral found in the 





