TREPONEMATA 579 
Treponema pallidum: an average or normal type; a type thicker than 
the average; and a type thinner than the averao:e; each of which 
induces somewhat different lesions in experimental animals. The 
thicker type is said to produce very dense, nodular lesions in the testes 
of rabbits; the thin type incites a more dift'use induration. The three 
types present no noteworthy cultural differences. Xoguchi suggests 
that these morphological and pathological variations observed in cul- 
tures of Treponema pallidum may constitute racial differences within 
the species.' 
The ends of the organisms are attenuated and merge almost imper- 
ceptibly into finely-pointed terminal filaments, one at each end. The 
morphology of the Treponemata varies somewhat in artificial media, 
according to the conditions of growth. According to Xoguchi, the 
typical organisms are only observed in special media where the condi- 
tions of culture are strictly anaerobic. The admission of even slight 
amounts of oxygen produces changes in their appearance. Reproduc- 
tion, according to Schaudinn-' and X'oguchi,^ takes place typically by 
longitudinal fission rather than by transverse fission, as was claimed by 
Levaditi and others. This would suggest a relationship with the pro- 
tozoa rather than with the true bacteria. It is very probable, however, 
that this is an unusual process, and available evidence indicates that 
transverse fission is the characteristic method of reproduction. The 
organisms show relationships both with the bacteria and the protozoa. 
Treponemata are actively motile in young cultures, particularly in 
media which are fiuid or semi-fiuid. In agar of ordinary density the 
motility is considerably lessened or even absent. The motility is 
i)rought about by the activity of the polar fiagella mentioned above. 
The character of the motion is twofold: a rotation about the long 
axis, and a true progressive motion. The resultant motion is like 
that of a corkscrew. Undulatory contractions of the organisms have 
also been observed. Xo capsules have been disco\'ered and no spores 
are produced. It has been claimed that an undulatory membrane 
has been demonstrated on Trei)onema pallidum, but this observation 
has not been adequately confirmed. Treponema pallidum does not 
stain with ordinary anilin dyes, it is non-acid-fast and cannot be 
stained by Gram's method. The organisms may be demonstrated 
in the living state on suitable material scraped from syphilitic lesions 
or stained by special methods (vide infra). 
Isolation and Culture.— Various successful attempts to induce multi- 
plication of Treponemata, both /// vivo and in vitro, are on record. 
' Nichols Mour. Exp. Med., 1914, 19, .362) has described a Treponema isolated from 
the spinal fluid of a syphilitic which conforms morphologically to the "thick tyjje" of 
Xoguchi. It produces a rapidly developing lesion in the male rabbit when inoculated 
into the testicle. The incubation period is about two weeks and a half, and the organism 
tends to cause generalized secondary lesions in the eye and skin. It is not known 
whether this tendency toward generalized infection is peculiar to this particular strain 
or whether the thicker organisms possess in common this property. 
2 Arb. a. d. kais. Gesamte, 1907, 26, 11. 
3 Jour. Exp. Med., 1912, 15, 90. 
