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Journal of Experimental Medicine

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MORPHOLOGICAL CHARACTERISTICS AND NOMENCLATURE OF LEPTOSPIRA (SPIROCH3ETA) ICTEROH ~ E M O R R H A G I i E ( I N A D A A N D IDO).
B~ HIDEYO NOGUCIII, M.D.
(From the Laboratories of The Rockefeller Institute for Medical Research.)
PLATES 25 TO 29.

(Received for publication, February 27, 1918.)
In a previous communication, the writer reported the presence in American
wild rats of a spirochete morphologically and immunologically identical with the
Spirodu~ta icterol~morrhagke of Inada and his associates and also with the strain
isolated by Stokes from cases of infectious jaundice among British soldiers in
Flanders3 The European strains, which have now been isolated from cases on
the British, French, and Italian fronts, as well as from wild rodents captured
not only near the battle-lines but in regions remote from them, are undoubtedly
strains of the same organism. 2 Jobling and Eggstein8 have also found the same
spirochete recently among wild rats caught in Tennessee.
J u s t how, in nature, a rat becomes a carrier of the spirochete is nota t once apparent. I t is not improbable t h a t the contamination of afoodstuff b y the urine of an infected rat m a y transmit the organism.toother rats; or the animal m a y become infected b y feeding upon a n
infected dead rat, since a rat m a y be experimentally infected b yfeeding it with an infected foodstuff or with an infected tissue orx Noguchi, H., J. Exp. Med., 1917, xxv, 755.
* Costa, S., and Troisier, J., Presse m~d., 1916, lxxx, 526, 565. Courmont, J.,
and Durand, P., Bull. et mg'm. Soc. m~d. h~p., 1917, xli, series 3, 115. Clement, P.,
and Fiessinger, N., Presse m~d., 1916, Ixxx, 598. Gamier, M., Compt. rend. Soc.
biol., 1916, lxxix, 928. Manine, Cristau, and Plazy, Compt. rend. Soc. bid., 1917,
lxxx, 531. Wilmaers, L., and Renaux, E., Arch. m&t. Belges, 1917, Ixx, 115, 207.
Dawson, B., and Hume, W. E., Quart. y. Med., 1916--17, x, 90. Zironi, A., andCapone, G., Sperimentale, 1917, lxxi, 298. Aseoli, M., and Perrier, S., Gazz.
osp., 1916, xxxvii, 1618. Sisto, P., Sperimentale, 1917, lxxi, 361. Siccardi, P. D.,
and Bompiani, G:, Ann. ig., 1917, xxvii, 609. Moresehi, C., Policlinico, Sez.
Prat., 1917, xxiv, 265. Sampietro, G., Ann. ig., 1917, xxvli, 23.
3 Jobling, J. W., and Eggstein, A. A., J. Am. Med. Assn., 1917, lxix, 1787.
575

576

NOMENCLATURE

OF L E P T O S P I R A

ICTEI~OH2EMOI~RI-IAGI~

organ. Whatever the mode of preservation in nature, Spirochaeta
icterohcemorrhagiae is a common commensal among rodents.

Morphology.
The morphology of this organism has been the subject of much study by its
discoverers and by others, but its distinctive feature does not seem to have beenrecognized. Inada and his associates described the organism as a spirochetewith several irregular waves, the entire body being dotted with alternate brightand shadowy portions.4 Hiibener and Reiter, who described a similar picture,apparently believed that the organism had a series of minute knots, and hence
gave it the name Spirochcetanodosa,bThat these investigators overlooked the true structure must havebeen due either to the difficulty of observing the organism, even undera powerful dark-field illumination, or to the indistinctness of theminute spirals in a stained preparation. I t appears as an almost
smooth bodied, wavy organism, not unlike Spironema refringens
when fixed in methyl alcohol and stained with Giemsa's solution (Figs.
1, 2, and 3). As has been said in a previous paper# the naturalfeatures of the organism can be well preserved when it is fixed in
osmic vapor and then stained over night with Giemsa's solution.
In such a preparation it is stained light purple and is seen to consistof a very tightly and regularly wound cylindrical filameiat tapering
to sharply pointed extremities. The filament usually assumes agraceful hook at one or both ends, while the main portion may bestraight or slightly bent (Figs. 4 and 5). The number of spirals (notwaves) varies considerably according to the length of the specimen, which may be between 3 to 20, 30, or even 40/~, but the distance
between the apices of two spirals measures about 0.5 #. For example, a specimen measuring 9 /z would have eighteen spirals. The
thickness, or diameter of a cross-section, of the organism is nearly
uniform until it approaches the terminal portion, which may be soconveniently designated because of its tapering points and its hooked
attitude. The number of spirals in the terminal portion appears to
4 Inada, R., Ido, Y., Hoki, R., Kaneko, R., and Ito, H., J. Exp. Med., 1916,
xxlii, 377.
s Hiibener and Reiter, Deutsch. reed. Woch., 1916, xlii, 1.

m_oEYo No6vcm

577

be about six in all specimens, and it is this portion which exhibits thegreatest tendency to become bent to a semicircle. Unlike various
spironemata or treponemata, the spiral amplitude near the extremities is not noticeably less than that of the middle portion of theorganism.
In certain specimens the terminal portions are far less intenseljz
stained than the main portion (Figs. 1, 2, and 3). In the majorityof specimens, both terminal portions are bent to the same side (Figs.
5, 6, 13, 16, 17, 19, and 22), but in some they form hooks of opposite
direction (Fig. 4), unipolar hooks (Figs. 8, 9, 15, and 20), or are notbent at all (Figs. 11 and 12) ; and some are contorted (Fig. 18). In
the less well preserved specimens the spirals are no longer distinct but
appear as somewhat m0re deeply stained dots (Fig. 21). As has alreadybeen pointed out, under a powerful dark-field illumination the organism in rapid rotary motion seems to be surrounded by a halo. Thismay be only an optical effect, but a similar clear zone has been
noticed in the stained preparations of some specimens (Figs. 12, 15, 17,
and 23).
The dark-field picture of the organism is such that one may mistakethe minute spirals for refractive beads arranged diagonally or somewhat obliquely with respect to the axis of the organism (Figs. 24 and
27 to 33), as originally depicted by Inada and his associates andothers. But, as has been stated before, with a favorable and powerful illumination, the real structure can be revealed (Figs. 24, 25, and34).
Only a few of t h e photomicrographs represent the characteristically hooked forms (Figs. 26 and 28) as actually seen in active rapid
rotary motion in a free space, because it was difficult to photographthe organisms in motion, and as soon as motion ceases many of themlose the typical hooks. The large wavy undulations, however, (notthe elementary spirals), as assumed by the organisms when penetrating semifluid medium, are well shown in some of the specimens at
rest (Figs. 27 and 29 to 33). The remarkable flexibility of the organism in a semisolid medium is also shown (Figs. 27, 32, and 33).
These minute filamental organisms dart through the soft medium withgreat rapidity, first in one direction and then in another, searchingfor a loose spot which they can pierce through. When encountering

578

NOM~lgCLATU1LEOF LEPTOSPI1LAICTEROH~MORRHAGI2E

an impenetrable obstacle they reverse their progression and start anew.
A striking sight is thus presented by these little vermicular organisms
darting in all directions. A vibratory motion of the free portion of
the organism results when it is extricating itself from an entanglement. In an emulsion of infected liver one may encounter a tangle ofseveral actively motile organisms (Figs. 24 and 25), while in a culture
several weeks old a mass of hundreds of motile spirochetes may befound (Fig. 35).
The European (Figs. 36 to 57) and Japanese (Figs. 58 to 68) strains
have all the morphological features given for the American strain. It
might be mentioned here that the elementary spirals in the terminal portion are much smaller in number and less regular in the stained
specimens of the European strain, but this may be due to imperfect fixation of the organism, because under the dark-field microscope
the spirals are equally close and regular.
Classification.
Characteristics

of Different Genera of Spiral Organisms.

In order to determine the systematic position of the organism of infectious jaundice, it may be well to review here the characteristics ofvarious genera of spiral organisms. Through the recent investigations of Gross, 6 Zuelzer/ Dobell, 8 Gonder, 9 Swellengrebel,1° andothers, the organism for which Ehrenberg created the term Spirochceta
in 1838 is now known to be distinct from the majority of so calledspirochetes. It consists of a long, highly flexible, central axial filament surrounded by a regularly wound layer of protoplasm, usuallyof great length (200 to 500 #), and is free living in fresh or marine
water (Fig. 108). Neither a membrane nor a flagellum is present.
Multiplication takes place by transverse fission. The organisms Gross, J., Centr. Bakteriol., lte Abt., Orig., 1912, lxv, 83.
Zuelzer, M., Arch. Protistenk., 1912, xxiv, 1.
s Dobell, C., Proc. Roy. Soc. London, Series B, 1912, lxxxv, 186.
g Gonder, R., Spironemacea(Spirochaeten),in yon Prowazek, S., Handbuch derpathogenen Protozoen, Leipsic, Liefg. 6, 1914, 671.
10Swellengrebel,N. H., Ann. Inst. Pasteur, 1907, xxi, 448; Compt. rend. Soa.
blol., 1907, lxii, 213.

HIDEYO NOGUCHI

579

creeps along the surface of an object but does not swim. Only four
species belonging to this genus have been described. The organism
under discussion does not belong to it.
Cristispira and Saprospira.--For a limited variety of coarse, actively motile spiral organisms infesting the crystalline styles of certain mollusca, the genus Cristispira was proposed by Gross in 1910. it
The characteristic features are: the presence of a membranous structure running spirally from one end of the body to the other, assuming
the aspect of a crista or ridge; the chambered structure of the body;the absence of a terminal filament; and the existence of a strong,
flexible membrane (Figs. 104 to 106). According to Gross, reproduction
may be effected by multiple transverse fission or sporulation, though I
have failed to confirm the occurrence of sporuPation. More than adozen species have been described, but from personal observations I
doubt whether these so called species are sufficiently characteristic
to' be so distinguished. The type organism was first described byCertes in 1882 TM as found in oysters, and was known as Spirochaeta or
Trypanosoma balbianii. Another genus, Saprospira, was proposed by
Gross in 1912 ~3for a few varieties of spiral organisms in mussels which
differed from the cristispir~e in not having a crista (Fig. 107). The
organism in question, however, belongs to neither of these genera.
Spironema and Treponema.--Next in order is the large group of smallparasitic spiral organisms commonly called spirochetes. Among them
are the causative agents of syphilis and yaws (Figs. 69 to 72 and 103)and of relapsing fevers i n m a n and animals (Figs.94 to 100), non-pathogenic parasites in certain rodents, and various saprophytic types onor about the oral, alimentary, or genital mucous membranes (Figs. 73
to 93). Their essential feature is a spiral flexible body with terminal
filaments, but no undulating membrane. They seem to multiply bytransverse as well as longitudinal fission. The rigidity of the curves
differs greatly in different organisms, some becoming almost flat at
death or constantly changing the waves by oscillatory undulation,others retaining their regular curves even during motion or after death.
The whole group has been called Spirochcetceor Spirilla, in spite of the
11 Gross, J., Mitt. zool. Station Neapel, 1910-13, xx, 41.
12 Certes, A., Bull. Soc. zool. franc., 1882, vii, 347; 1891, xvi, 95.
13 Gross, J., Mitt. zool. Station Neapel, 1910--13, xx, 188.

5~0

NOMENCLATURE OF LEPTOSPIRA I C T E R O H ~ E M O R R H A G I ~ E

fact that they have no affinity with the real spirochete or non-flexible
spirillum. Gross includes them in the genus Spironema, a term introduced by Vuillemin14 in 1905 to distinguish Schandinn's organism of
syphilis from those with less rigid spirals. Dobell,* however, believes
that the term Treponema, as proposed by Schaudinn 1~himself in 1905
for his organism, should be employed to designate all these minuteparasitic varieties. Gonder 9 takes a more conservative stand andupholds the distinction made by Schaudinn between the treponema
type and that with less constant curves. For example, Gonder retains the genus Spironema for the latter arm Treponema for the former
type. I agree with Gonder in this respect, as the general featuresare sufficiently distinct to enable one to differentiate the two groups.

Nomenclature of Leptospira (Spiroch(eta) icteroh¢emorrhagice.
The striking differences between the organism of infectious jaundice
and all the other so called spirochetes, or rather spironemata andtreponemata, are apparent at a glance. The closely set, regularspirals of the organism of Inada and Ido remain unmodified during its
rotary, spinning motions in a free space and when it is piercing asemisolid medium. While in motion in a free space, the whole body
appears tightly drawn into a straight line, except for the usual hookformation of one or both terminal portions. When one end is extended and straight and the other semicircularly hooked, the organism usually progresses in the direction of the straight portion andseems to be propelled from the rear by the rotating hook (Figs. 8, 9,
15, and 20). A specimen with both ends hooked remains stationary
in spite of its rapid rotary motions (Figs. 13, 16, and 19). By
straightening one end or the other alternately, the organism changes
its progression from one direction to the opposite one. When theorganism penetrates a soft medium, changing direction very rapidly,
it seldom shows hooked ends (Figs. 11, 12, 29, 30, 32, and 33). In
this sort of movement the body assumes wide wavy undulations suchas are seen in an active specimen of Spironema refringens. The
behavior of the organism in semisolid medium is different from that
14Vuillemin, P., Compt.rend. Acad., 1905, cxl, 1567.
1~Schaudinn, F., Deutsch.reed. Woch.,1905, xliii, 1728.

~rm~.Yo NoG~rc~_t

581

in a free space. The persistence of the minute elementary spirals
at all times is a feature which distinguishes this organism from any
treponema or spironema. The depth of the spirals does not exceed thediameter of the body, a fact unknown among other so called spirochetes.
A diligent search by means of various staining methods, as well as bydark-field illumination applied to cultures of different ages, has notdemonstrated a terminal flagellum or peritrichal flagella or membranes. It is well to recall at tMs point that in old cultures of all the
spironemata or treponemata I have isolated I have been able to demonstrate the presence of a terminal filament, even when it was observedwith di~culty in uncultivated specimens. This organism, however, as
far a s we know at present, moves by means of its terminal portions.
Moreover, unlike spironemata and treponemata, it withstands theaction of 10 per cent saponin. Clearly it does not belong to eitherof these genera, but must remain in a class by itself until other similarorganisms come to our observation. The nearest approach to it inmorphological and biological respects is Spirochc~ta biflexa, which wasisolated by Wolbach and Binger TM in 1914 from a filtrate of stagnant
water taken from the shore of a fresh water pond near Boston. Thereis a great similarity between the two organisms. Both are filterable
through Berkefeld filters. Wolbach and Binger did not succeed in
obtaining a second generation in culture, and no tests of pathogenicity
for experimental animals were made.
For the reasons which have been discussed, it seems justifiable toinclude the type of organism in question under Leptospira (X¢Trr6,
fine, + az~pa, coil), as has already been proposed. I
The genera with their type organisms are presented below. T h emeasurements of each of these representative members and thecharacteristic features used for identification of the genera are considered. There is little difficulty in distinguishing Spiroch~ta, Saprospira, Cristispira, and Leptospira from one another. But the distinctlon between Spironema and Treponema depends chiefly upon therigidity and regularity of the spirals which are characteristic of the
treponemata. Under natural conditions this difference is so marked
that there should be no confusion in classification, but under cultural
t6 Wolbach, S. B., and Binger, C. A. L., Y. Med. Research,1914, xxx, 23.

582

I~OMIE~CLATURE OF LEPTOSPIRA ICTEROH~N[ORRIIAGI~

conditions the spirals of the spironemata acquire such rigidity andregularity t h a t they, too, m a y be called treponemata. I)obell 8 and
Gross, 6 independently of each other, and without a n y knowledge as
to the morphological modifications dtle to cultivation, regarded thedistinction between Treponema and Spironema as insufficient tomaintain two separate genera, and Dobell chose the term Treponema
and Gross Spironema for the same group of organisms. In m yopinion the characteristics of Treponema and Spironema, undernatural conditions, are sufficiently pronounced to justify retaining thetwo terms in classification. Neither Treponema nor Spironema has
a n y feature which is likely to be confused with those of the otherfour genera referred to above. Text-fig. 1 shows the types mentioned
below.

Genus.--Spirochceta (Ehrenberg, 1838). Type Organism.--Spirochcetaplicatilis(Ehrenberg, 1838) (Fig. 108). Measurements.--Length, 100 to 500 t*; blunt end.
Diameter, 0.5 to 0.75~; cylinc~rical. Spiral amplitude, 2 u; regular. Spiral depth,
1.5 ~; regular. Waves, several, large, inconstant, irregular. Axial Filament.-Distinct in stained specimens; flexible; elastic. Chambered Structure.--Absent.
Membrane.--Absent. Crista.--Absent. Terminal Finely Spiral Filament.-Absent. Flagella.--Absent. Highly Motile End Portion.--Absent. Division.-Transverse. Habitat of Genus.--Free living in fresh or marine water. Other
Species.--Plicatilis marina, plicatilis eustrepta, stenostrepta, daxensis. Staining
Properties of Axial Filament and Cell Membrane.--Axial filament consists of chitin
or cutin-like substance. Stains violet by Giemsa's solution and gray by ironhematoxylin. Staining Properties of Body.--Plasmic spirals of the body stain
with eosin, rubin, etc. Contain volutin granules. TrypsinDigestion.--Axial filament resistant. Bile Salts (10 Per Cent).--Becomes shadowy pale but is notdissolved. Saponin (10 Per Cent).--Lives 30 minutes. Later becomes shadowy,
but is not dissolved.
Genus.--Saprospira (Gross, 1911). Type Organism.--Saprospira grandis(Gross, 1911). Measurements.--Length, 100 to 120 ~,; obtuse end. Diameter,?u; cylindrical. Waves, large, inconstant, shallow, irregular, 3 to 5 in number.
Sometimes almost straight. Axial Filament.--Absent. ChamberedStructure.-Present. Membrane.--Distinct, flexible, elastic. Crista.--Absent. Terminal
Finely Spiral Filament.--Absent. Flagella.--Absent. Highly Motile End Portion.--Absent. Divlslon.--Transverse. Habitat of Genus.--Free living in foraminiferous sand. Other Species.--Nanf~.
Genus.--Cristispira (Gross, 1910). Type Organism.--Cristlspira balbianii(Certes, 1882) (Figs. 104 and 105). Measurements.--Length, 45 to 90 u; obtuse
end. In stained preparations the end may be sharply pointed, but this is due

HIDEYO NOGUCHI

583

to shrinkage by fixing reagents. Diameter, 1 to 1.5 u; cylindrical. Waves, 2 to 5,
sometimes more, large, irregular, shallow. In a dying specimen the waves may
be more numerous and regular. Axial Filament.--Absent. Chambered Structure.Present. Membrane.--Distinct, flexible, elastic. Crista.--Present, a ridge-likemembrane. Spirally wound body. Terminal Finely Spiral Filament.--Absent.

Flagella.--Absent. Highly Motile End Portion.--Absent. Division.--Transverse. Habitat of Genus.--Parasitic in the alimentary canals of shell-fish. Other
Species.--Ostrce, anodontce, modiolce, veneris, tapetos, chamce, etc. Staining Prop-

TExT-FIG. 1. Diagram contrasting the characteristic features and relative
proportions of Spironema, Treponema, Cristispira, Saprospira, Spirochceta, andLeptospira. The scale in microns is given in the upper left-hand corner ofthe figure.

erties of Axial Filament and Cell Membrane.--Membrane behaves like chitin or
cutin substance. Stains violet by Giemsa's solution and light gray by iron-hematoxylin. Staining Properties of Body.--The body is alternately stained red andbluish violet and the crista red by Giemsa's solution. Iron-hematoxylin bringsout sharp septa and a layer of chromatin granules. Trypsin Digestion.--Membrane
resistant. Crista and chambers disappear. Bile Salts (10 Per Cent).--Crista
quickly destroyed. Body not attacked. Saponin (10 Per Cent).--Crista becomes
fibrillar, then indistinct, Body not affected.

584

NOMENCLATUI~E

O F L E P T O S P I R A ICTEI~OII~MORRI-IAGI2E

Genus.--Spironema (Vuillemin, 1905). Type Organism.--Spironema recurrentis(Lebert, 1874 tT) (Figs. 94 to 96). Measurements.--Length, 8 to 16,; pointed ends.
Diameter, 0.35 to 0.5 #; cylindrical or slightly flattened. Spirals, large,wavy, inconstant, about five in number. Closer and more regular in cultures. Axial Filament.--Probably present. Chambered Strueture.--Absent. Membrane.--Delicate, flexible, double contoured. Crista.--Absent. Terminal Finely Spiral Filament.--Present, easily seen in cultures. Flagella.--Absent. Highly Motile End
Portion.--Absent. Division.--Transverse, possibly also longitudinal. Habitatof Genus.--Numerous pathogenic and non-pathogenic varieties. Other Species.
--Carteri, kochi, novyi, duttoni, berbera, aegyptica, gallinarum, anserina, theileri,equi, muris, eugyratum, microgyratum, buccalis, refringens, etc. Staining Properties of Axial Filament and Cell Membrane.--Membrane difficult to differentiate.
Staining Properties of Body.--Stains violet by Giemsa's solution. Bile Salts (10Per Cent).--Disintegration complete. Saponin (10 Per Cent).--Immobilized
in 30 minutes then broken up in a few hours. In some there is an axial filament
laid bare.
Genus.--Treponema (Schaudinn, 1905). Type Organism.--Treponema pallidum(Schaudinn and Hoffmann, 1905is) (Figs. 69 to 72 and 103). Measurements.Length, 6 to 14 ~; pointed ends. Diameter, 0.25 to 0.3 ~; cylindrical. Spiralamplitude, 1 ~,; regular, rigid. Spiral depth, 0.8 to 1 ~; very constant. Waves,
one or more slight undulating curves may be present. Axial Filament.--Doubtful. The whole seems to consist of a spirally wound axial filament. Chambered
Structure.--Absent. Membrane.--Doubtful; if there is one it must be flexible.
Cris'ta.--Absent. Terminal Finely Spiral Filament.--Present. Easily seen in cultures. Flagella.--Absent. Highly Motile End Portion.--Absent. Division.Transverse or possibly also longitudinal. Habitat of Genus.--Two pathogenic andseveral harmless parasites. Other Species.--Pertenue, microdentium, macrodentium,

mucosum, calligyrum, minutum. Staining Properties of Axial Filament and Cell
Membrane.--Membrane not recognizable. Staining Properties of Body.--Stains
pink by Giemsa's solution. Trypsin Digestion.--Resists digestion for many days.
Bile Salts (10 i~er Cent).--Disintegration complete. Saponin (10 Per Cent).-Broken up in time.

Genus.--Leptospira (Noguchi, 1917). Type Organism.--Leptospira ictero
hcemorrhagi¢ (Inada and Ido, 1914) (Figs. 1 to 68, 101, and 102). Measurements.-Length, 7 to 9 to 14 ~; exceptionally 30 to 40 ~; pointed ends. Diameter, 0.25 to
0.3 ~; cylindrical. Spiral amplitude, 0.45 to 0.5 ~; regular, rigid. Spiral depth,
0.3 #; regular. Waves, one or more gentle wavy curves throughout the entire
length~ When in a free space, one or both ends may be semicircularly hooked,
while in semisolid media the organism appears serpentine, waved, or bent. Its
flexibility is most striking. Axial Filament.--Not recognized. ChamberedStruc17 Lebert, H., Riickfallstyphus, Flecktyphus und Cholera, in von Ziemssen, H.,
Handbuch der speciellen Pathologie und Therapie, Leipsic, 1874, ii, 267.
zs Schaudinn, F., and Hoffmann, E., Arb. k. Gsndhtsamte., 1905, xxii, 527.

HIDE¥O NOGUCn-~585

ture.--Absent. Membrane.--Not recognized. Crista.--Absent. Terminal Finely
Spiral Filament.--Not recognized. Flagella.--Absent.
Highly Motile End
Portion.--WeU developed in the last six to eight spirals. Di~ision.--Transverse.
Habitat of Genus.--One pathogenic and one possibly non-pathogenic variety
known. Other Species.--Biflexa (Wol_bach and Binger). Staining Properties of
Axial Filaraent and CellMembrane.--Membrane not recognizable. Staining Properties of Body.--Stains reddish violet by Giemsa's solution. Bile Salts (10Per Cent).--Easily dissolved. Saponin (10 Per Cent).--Completely resistant.
The comparative dimensions of these representative organisms
m a y be shown b y putting side b y side the diameter, spiral amplitude,
spiral depth, and length of each, taking the diameter of the finest
member, Leptospira icterohvemorrhagice, as a unit of comparison (TableI).
TABLE I.
Organism.
Leptospira icterohremorrkagice..
Treponema p a l l i d u m . . . . . . . . .
S p i r o n e m a obermeieri . . . . . . . . .
Cr~*tispira balbianii . . . . . . . . . .
S a p r o s p i r a grandis . . . . . . . . . . .
Spirock~eta plicatilis: . . . . . . . . .

Thickness.

(0.25 ~)
1.2 (0.3/*)

Spiralamplitude.

Spiral depth.

2 (0.5/*)

1.2 (0.3/*) 56 (14/*)
3.6 (0.9/*) 48 (22/*)6 (1.5 t,) 32 (8 ~)
24 (6/*) 200 (50/*)400 (100/*)
8 (2/*)
6 (1.5/*) 600 (150/*)

4 (1 t,)2 ,(o.s/*)s (2.2/*)

12 (3 ~)
60 (25/*)5 (2.2t,)
32 (8/*)
3 (o. 75/*) 18 (4.5 t,)

Length.

One m a y obtain the comparative proportions for each genus b yusing the diameter of its representative member as a unit of comparison, as in Table I I .
TABLE II.
Organilm.

Thickness.

Spiralamplitude.

Spiral depth.

Length.

Spiroch~ta plicatilis....
1 (0.75/*)
Saprospira grandis.
1 (1.2 t~)
Cristispira balbianii
2 (2.2 z)
Spironema oberraeieri
1 (0.5/*)
Treponema pallidum.
1 (0.3 t,)
Leptospira icteroheemorrhagice... 2 (0.25 ~)

6 (4.5/,)7(8~)
a3 (15/*)6(3/*)
3.3 ( 1 ~)
2 (0.S ~)2 (1.5 u)
1.8 (2/*)5 (6/*)
3 (1.S/*)
3 (0.9 t*)
1 (0.25 ~)2oo (150 ~,)83 (100~)
41 ( so ~,)16 ( 8 ~)4o (a2/*)56 (14/*)T h e proportions are distinctive for each genus, and form, with other
differentiating features already discussed, a fairly well establishedbasis for the classification of these spiral organisms, hitherto so indis-

~86

I~OMENCLATUEE OF LEPTOSPIRA ICTEROH~MORP,HAGI~

criminately called by the general name of spirochetes. It would bedesirable, in describing a new spiral organism, to place it in one of thesix classes discussed, since under the vague name of spirochete noone can visualize the actual features of the organism in question,
while if it is called Leptospira, for example, certain definite features areconnoted, and confusion with other so called spirochetes is avoided.
This is particularly important when one is examining specimens ofurine such as those from certain cases in which a Leptospira or a
Treponema may be present alone or together, as in a study of trench
infections. Patterson 19 and NankiveLl and Sundell2° discovered thelatter type in cases of trench fever of unknown origin, while theformer has been found responsible for a number of cases of various
trench affections3I,~2
A brief note m a y be made of the relation of Lepgospira to a comparatively minute species of spirochete, Spirocheta stenostrepta, described by Zueizeff (Figs. 109 and 110). The organism was found instagnant water with Spirochceta plicatilis. It has a diameter of 0.25
and a length of 20 to 60/~, seldom reaching a length of 200 #. In a
short specimen which measured 13/~ there were eleven spirals. In life
an axial filament was recognized. Here the leptospira can be distinguished by its lack of an axial filament and its closer spirals. In thelatter respect certain oscillatorial organisms such as Spirulina vesicolor(Figs. 111 and 112), or Spirulina tenuissima have a superficial resemblance to leptospira, but their multicellular structure, which canbe demonstrated by subjecting them to a preliminary treatment withtrypsin solution before staining, shows them to be very different.
Each coil here represents an individual cell separated from the adjoining cells by walls. The spirulina has blunt ends and does notexhibit the active, brusque movements characteristic of leptospira.
19 Patterson, S. W., J. Roy. Army 2fled. Corps, 1917, xxix, 503.
s0 Nankivell, A. T., and Sundell, C. E., Lancet, 1917, ii, 672, 836.
st Couvy, L., and Dujarric, R., Compt. rend. Soc. biol., 1918, lxxxi, 22.
~ Dudgeon, L. S., Lancet, 1917, ii, 823.

HtDEYONOGUCI~I

587

SUMMARY.
The present study deals with the morphology and systematic
position of the causative agent of infectious jaundice. There areseveral features which are not found in any of the hitherto known
genera of Spirochmtoidea which led me to give this organism an
independent generic name, Leptospira, denoting the peculiar minuteelementary spiral s running throughout the body. The absence ofa definite terminal flagellum or any flagella, and the r e m a r k a b l eflexibility of the terminal or caudal portion of the organism areother distinguishing features. Unlike all other so called spirochetes
the present organism resists the destructive action of 10 per centsaponin.
A detailed comparative study of related genera, including Spiroch~ta, Saprospira, Cristispira, Spironema, and Treponema, has been
given with the view of bringing out more strongly the contrast
between them and the new genus.
A study has been made to discover whether any differential
features exist among the strains of Leptospira icterohcemorrhagice
derived from the American, Japanese, and European sources, but
none has been found.
I t is hoped that the creation of a new genus m a y qacilitate amore exact morphological description than has hitherto been possible, due to the vague use of the term Spirochceta which indiscriminately covered at least six large genera of spiral organisms.
EXPLANATION OF PLATES.
PLATE 25.
Figs. 1 to 23 show the morphological features of the American strain of Leptospira icterohcemorrhagice.instained preparations.
FIG. 1. Leptospiraicterohcemorrhagitein the blood of an experimentally infected guinea pig, showing irregular refringent waves, but no minute elementaryspirals. Methyl alcohol fixation and Giemsa's solution. X 1,000.
FIG. 2. The same in a liver emulsion from a similar animal. Except for the
few moderate undulations of the body, there is no indication here that these are
spiral organisms. Methyl alcohol fixation and Giemsa's solution. X 1,000.
FIG. 3. The same in a kidney emulsion. Fixation and staining the same asabove. × 1,000.

588

I~OM.EI~CLATURE O1~ LEPTOSPIRA ICTEI~Ott/EMOI~I~HAGI2E

FIG. 4. The same in a blood specimen of an infected guinea pig. Fixationand staining the same as above. X 1,000.
Figs. 1 to 4 are intended to show the appearance of the leptospirm in an airdried specimen, fixed with methyl alcohol, and stained with Giemsa's solution.
They do not show any elementary spirals and appear as smooth, somewhat wavy
filaments.
FIQS. 5 to 11. Leptospira icterohcemorrhagice in stained preparations from aculture in its first generation on the 5th day. They were fixed when moist by
osmic acid vapor for 2 minutes, then hardened in absolute alcohol for 30 minutes,
and after being thoroughly washed in distilled water, were stained over night with
Giemsa's solution (1:20 dilution). I n these preparations there were many instances where the fixation and staining were not so satisfactory as in the specimens
shown in these photomicrographs. A careful examination makes possible recognition of the closely set, minute, regular spirals throughout the entire length ofthe organism. With a magnification of 1,000 they are almost too minute toenable one to count the number of the spirals. X 1,000.
F i t s . 12 to 23. Leptospffa icterohtemorrhagice magnified 3,000 times, whichbrings out the features more distinctly. All except Figs. 21 to 23 show the elementary spirals well. There are ten to twelve spirals to every 5 v, making the distance between the apex of one spiral to that of the next about 0.5 v. The terminal
portions of the organisms are recognized by the gradually decreasing diameterand the coloration, which is lighter than that of the main portion of the
body. These end portions seem to possess about six elementary spirals andmeasure about 3~ in length. They exhibit remarkable activity and flexibility
and serve as propellers in progression in free space and as feelers in guiding theorganism through a semisolid medium. Note Fig. 12.
Fig. 18 shows a specimen fixed probably during a somersault movement.
The elementary spirals appear as dimly stained cross bars (imperfect
fixation).
Fig. 21 shows three organisms attaching themselves to a red corpuscle. The
spirals are not distinctly brought out, but one recognizes them as more intensely
stained dots, arranged obliquely with respect to the optical axis of theorganism.
Fig. 22 (also Figs. 13 and 19) shows a specimen fixed while rotating on its axis
in a free space. The organism was otherwise stationary, as shown by its symmetrically bent hooks. Compare with Fig. 20, which has one hook, and therefore must be proceeding in the direction of the straight end.
The two specimens in Fig. 23 show no definite direction of progression. The
spirals, though not well fixed, are fixed sufficiently for recognition.
In Figs. 12, 15, 17, 21, and 23, there is a clear space, or halo (about 0.15 ~, wide)
about the organisms along the entire length. Whether this clear zone, or halo, indicates the presence of a less chromatic membrane enveloping the organisms or ismerely due to the dispersion of particles (culture media) from their immediateneighborhood by their rotary movements cannot yet be determined.

ttIDEYO N O G U(;/d_t589

PL~I"E 26.
FIGS. 24 to 35.

Specimens of the American strain of Leptospira icterohcemor-

rhagice as seen under the dark-field microscope.
Fig. 24. The organisms in a liver emulsion of an experimentally infected guinea
pig. They are in resting position and show no characteristic hooked ends. One
isolated leptospira has both ends hooked, but not typically, as it would be while
actively rotating or progressing in a free space. The spirals appear as regularly
set cross bands. X 1,000.
Figs. 25 and 26. A higher magnification of the same specimens. The finely set
regular spirals are distinctly shown at the right in Fig. 24, and the cross-barred or
dotted aspect of the spirals is shown in the other two of the same figure and alsoin Fig. 26. X 3,000.
Fig. 27 (X 1,000) and Figs. 28, 29, and 30 (X 3,000) show the leptospir~e inthe kidney emulsion of an infected guinea pig. Except for the specimen at thecenter of Fig. 27, the organisms are in undulatory positions, with gracefully
wound, rather loose waves. This position almost always indicates that the organisms are in a semisolid medium, which they are penetrating by means of spiral
propulsion. They often remain in the same position for some time before renewing their efforts to extricate themselves. Their dotted or cross-barred appearance remains unmodified under these circumstances.
Fig. 31 (X 1,000) and Fig. 32 (X 3,000) show similar but more pronounced
characteristic features.
Fig. 34. The minute elementary spirals are plainly seen in the three entangled
leptospirm in the right upper corner, while in three organisms of Fig. 33 they arerecognizable only as dots or bars. × 3,000.
Fig. 35. A large mass of leptospirm in a fluid culture 3 weeks old. They growconsiderably longer in such a medium and form a mass of entangled organisms
having the same minute elementary spirals as uncultivated specimens. X 1,000.
PI~

27.

Figs. 36 to 57 represent the British strain (Stokes) of Leptospira @terohc,mor-

rhag~.
FIG. 36. A Fontana preparation of the leptospirm in the liver emulsion of an
infected guinea pig. The elementary spirals can hardly be distinguished. ×
1,000.
FIC. 37. A badly fixed osmic acid-Giemsa preparation, in which one of theorganisms on the extreme right appears as a negative image with minute elementary spirals well brought out. The dye settled about "the leptospira without
staining the organism itself. X 1,000.
FIGs. 38 to 43. A preparation better fixed with osmic acid vapor and wellstained with Giemsa's solution. The leptospir~ were cultivated 7 days at 28°C.
In none of them is there any difficulty in discerning the individual elementary

590

N O M ~ E N C L A T U R E OF LEPTOSPIRA I C T ~ I ~ O I I ~ r O ~ G I / E

spirals throughout the entire length of the organism. Perhaps owing to imperfect fixation, the elementary spirals in the terminal portions are less numerous
and the spiral depth is shallower than in the main portion, which also takes ona more intense stain. In the majority of specimens the s p i r a l amplitude of themain portion is about the same as that of the American or the Japanese strain(0.5 ~,). There are a few specimens, however, which measure 0.6 ~, from one spiralto the next. × 1,000.
Fm.s. 44 to 52. The same. × 3,000.
FIos. 53 to 57. Dark-field views of the leptospira. Figs. 53, 56, and 57 arefrom a fluid medium, and Figs. 54 and 55 from a semisolid medium. × 1,000.
PLATE 28.

Flos. 58 to 68. Dark-field views of the Japanese strain of Leptospira iclerohtemorrhagite from a 7 day culture on semisolid medium. Figs. 58 to 62 are magnified 1,000 times and Figs. 63 to 68, 3,000 times. These photographs show theremarkable flexibility of the tight, elementary spirals of the organisms. The numerous circularly coiled specimens suggest the peculiar hoop-like coiling form of somespecimens of Cristispira balbianii in the crystalline styles of oysters.
FIGS. 69 to 72. Dark-field views of Treponema pallidum which are given here
for comparison with the leptospir~e. Their larger spiral amplitude and spiral
depth, and their rigidity are sufficiently differentiating. Figs. 69 and 71 are
magnified 1,000 times, and Figs. 70 and 72, 3,000 times.
PLATE 29.

Some of these photomicrographs are from stained and some from dark-field
preparations. They are reproduced here to illustrate the differential characteristics of several constituent genera of the family of Spiroch~etoidea (Dobell). ×
1,000.

Treponema Group.
FIGS. 73 to 76. Dark-field views of a minute treponema (Treponemaminutum,n. sp.) found in a smegma. Their average spiral amplitude is 0.9 to 1 u, spiral
depth, 0.2 to 0.5 u, average number of spirals, eight to ten in 7 to 9 ~,, and thickness, 0.3 u.
FIGS. 80 to 83. Treponema calligyrum in smegma. Spiral amplitude, 1.75 u,
depth, 0.5 to 1 u, four to seven spirals in 7 to 12 u, thickness, 0.4 to 0.5 t,.
FIG. 84. The same from a culture.
FIG. 85. Treponeraamlcrodentium from the mouth.
FIG. 86. The same from a culture.
FIG. 88. Treponema macrodentium from a culture.
FIGS. 92 and 93. A treponema from the urine of a child, resembling the smallest smegma treponema (Figs. 73 to 76).

HIDE¥O NOGUCHI591

Spironema Group.
FIGs. 77 and 78. Spironema refringens from smegma. Spiral amplitude, 2 to
2.75 u; spiral depth, 0.5 to 1.5 u; four to eight spirals in 11 to 16u; thickness, 0.7 •.
FIG. 79. The same from a culture.
FIG. 87. Spirone~a vincenti from the mouth.
FIGs. 89 to 91. Spironema buccalis from the mouth. Spiral amplitude, 2.75
to 3.7 u; spiral depth, 0.7 to 1 u; four to seven and one-half spirals in 11 to 17 u;
thickness, 0.5 to 1 u.
FIGS. 94 and 96. Spironema recurrentis in a culture.
FIG. 95. The same in the blood of an infected mouse.
FIG. 97. Spironema duttoni in a culture.
FIG. 98. Spironema kochi in a culture.
FIG. 99. Spironema gallinarum in a culture.
FIG. 100. Splronema novyi in the blood of an infected rat.

Leptospira Group.
FIG. 101. Leptospira icteroh~emorrhagice, American strain. × 1,000.
FIG. 102. Leptospira icterokemorrhagize, Japanese strain. × 1,000.
FIG. 103. Treponema pallidum for comparison. Same magnification.

Cristispira Group.
FIG. 104. Dark-field view of Cristispira balbianii from oysters obtained near
Woods Hole.
FIG. 105. The same. Osmic acid fixation. Stained with Giemsa's solution.
FIo. 106. Cristispira veneris (?) from clams obtained near Long Island Sound.
Sublimate alcohol fixation and Heidenhaln,s iron-hematoxylin.

Saprospira Group.
FIG. 107. An organism possibly belonging to this genus.
me from oysters obtained near New York.

It was cultivated by

Spiroch~eta Group.
Fib. 108. Spiroch~eta plicatilis. Sublimate acetic-acid-alcohol fixation andiron-hematoxylin (after Zuelzer).
FIGS. 109 and 110. Spirochcetaaenostrepta (after Zuelzer).

592

NOMElqCLATUI~ OF LEPTOSPLKA ICTEROH2EMORRItAGI,~

Spirulina Group.
FIG. 111. Spirulina ~esicolor. This organism does not belong to the familyof Spirochmtoidea, but on account of its close spirals it is shown here. Iodinealcohol and Delafield hematoxylin (after Zuelzer).
FIG. 112. The same, at another plane of focus, where the innermost structure
is not brought out as in Fig. 111.

THE JOURNAL OF EXPERIMENTAL MEDICINE VOL. X X V I I .

PLATE 25.

(Noguchi: Nomenclature of Leplosplm ~cteroha*~morrkaglm.)

THE JOURNAL OF EXPERIMENTAL MEDICINE VOL. XXVII.

PLATE 26.

(Noguchi: Nomenclature of Leptospira icleroh~morrhagi~e.)THE JOURNAL OF EXPERIMENTAL MEDICINE VOL. XXVII.

PLATE 27.

(l~oguchh Nomenclature of Leptospira icterok~morrhagi~e.)THE JOURNAL OF EXPERIMENTAL MEDICINE VOL. X X V l l .

PLATE 28.

(Noguchi: Nomenclature of Leptosplra iaerok~morrhagi~.)

THE JOURNAL OF EXPERIMENTAL MEDICINE VOL. X X V I I .

PLATE 29.

(Noguchi: Nomenclature of Leptospira ic/*rok,aemorrhagi~e.)