TREPONEMATA 517 



is broken at an appropriate level with sterile precautions and some 

 of the turbid medium removed into fresh tubes of the same kind, 

 and the process repeated until pure cultures of the organisms are 

 obtained. If gas-producing bacteria are present the results are unsuc- 

 cessful as a rule. 



Products of Growth. The products of growth are unknown. Tre- 

 ponema pallidum does not produce a characteristic and disagreeable 

 odor which distinguishes it from cultures of other spirochetes in 

 artificial media. 1 



Pathogenesis. Animal. In 1903 Metchnikoff and Roux 2 trans- 

 mitted syphilis to a chimpanzee, and later infected other monkeys 



FIG. 75. Treponema pallidum, congenital syphilitic liver. 



with material from primary or secondary lesions in man. These 

 results have been amply confirmed by other investigators. The 

 incubation period averages about three to four weeks. It may be as 

 brief as two weeks or as prolonged as seven weeks. The lesion, his- 

 tologically indistinguishable from a chancre, appears soon after the 

 end of the incubation period at the site of inoculation; the regional 

 glands become enlarged and indurated. Secondary lesions appear 

 in about 50 per cent, of successful inoculations, usually four to five 

 weeks after a chancre appears. Skin lesions are somewhat indefinite, 

 but the mucous patches are readily recognized. No tertiary lesions 

 have been demonstrated in experimental inoculations into animals 

 with the virus of syphilis up to the present time. Recently Noguchi 3 



1 Noguchi, Jour. Exp. Med., 1912, xv, 99. 



2 Deutsch. med. Wchnschr., 1903, No. 50. 



3 Loc. cit., p. 96. 



