286 REPORT OF THE HARVARD AFRICAN EXPEDITION 
Chesney ! points out that there is a close parallelism between percentage of 
successful inoculations of syphilis obtained by Nichols in yaws rabbits, and 
the percentage of successful reinoculations obtained by others in syphilitic 
rabbits where heterologous strains of 7. pallidum were used for the second 
inoculation. Volgtlin and Dyer? have also recently produced evidence to 
show that treated syphilitic rabbits which are refractory to a second inocu- 
lation with syphilis, are refractory to inoculation with yaws virus. Kolle ’ 
found that seven syphilitic rabbits were all refractory to infection with yaws 
virus, while of fifteen rabbits infected with yaws, nine, or sixty per cent could 
be successfully infected with syphilis. In his experiments at least 120 days 
elapsed between inoculations. These experiments again suggest that the syph- 
ilitie virus may at least in some instances be of greater virulence.? Some of 
the experiments of Reasoner® to the effect that rabbits which have had yaws 
lesions of the testicle are not immune to intravenous inoculation of syphilis, 
also suggest such a view. 
Schébl and Miyao® conclude that the Treponema of syphilis is far more 
resistant to adverse conditions prevailing outside the tissues of the host than 
the Treponema of yaws. They say the ‘‘ Treponema of syphilis is panblasto- 
tropic. It can invade, multiply, and colonize all tissues. It does this with a 
mesoblastic preference and according to the law of sequence. It survives and 
produces lesions in the various tissues. The consequence is syphilitic mani- 
festations on the skin, the mucous membranes, the internal organs and the 
nervous tissue. Treponemas of syphilis invade the cardio vascular system and 
consequently the placenta, resulting in congenital syphilis.” They regard ‘‘the 
treponema of yaws an epiblastotropic. It invades, colonizes and produces 
lesions only in certain tissues, particularly the skin. Its invasion may extend 
to mucous membranes by extension per continuitatum from the skin. It lacks 
the mesodermic preference of the Treponema of syphilis. Consequently the 
internal organs, the nervous tissue and the cardiovascular system remain un- 
affected and the disease is not congenital.” 
The interpretation of some of these animal experiments may be compli- 
cated according to whether or not acquired immunity in syphilis is dependent 
upon foci of syphilitic infection somewhere in the body. Chesney,’ after re- 
viewing the evidence, apparently inclines to the view that during the course 
of syphilitic infection the host may develop an immunity and acquire a resis- 
tance against a second infection which may persist after the first infection has 
been eliminated by treatment. Kolle and Prigge,* on the other hand, from recent 
1 Chesney: Loc. cit., p. 525. 
2 Volgtlin and Dyer: Public Health Report, U. S. Pub. Health Ser. (1925), XL, 2511. 
3 Kolle: Loc. cit., p. 11. 
‘ Hifuka Kiyo (Japan Med. World [1929], LX, 299) has recently studied clinically and histologi- 
cally the metastatic skin eruptions in rabbits produced by intravenous injection of the viruses of syphilis 
and of yaws. He finds that in these animals the differences observed are only in degree and are not 
absolute. * Reasoner: Amer. Jour. Trop. Med. (1929), IX, 429. 
6 Schdbl and Miyao: Loc. cit., p. 108. 
7 Chesney: Medicine (1926), V, 503. 
8 Kolle and Prigge: Arbeit. aus dem Staatsinstitut f. Exper. Ther. u. d. Georg Speyer Hause zu 
Frankfurt A. M., Jena (1929), Heft 22, p. 18. 
