HIDEYO NOGUCHI 465 



and the protoplasm escapes. The appearance of attached spherical bodies (Fig. 24), 

 a common phenomenon in spirochetes, is due to minute extrusions of cytoplasm at 

 points of regional disturbance in the periplast. 



The essential structure of a treponema, therefore, is a spring-like axial filament, 

 and a layer of contractile protoplasm, inclosed in a delicate periplast. When suspend- 

 ed in an isotonic medium the body undergoes a rotatory motion whenever the pressure 

 of the contracting protoplasm stretches the axial filament. If the contractions and 

 relaxations of the protoplasm occur in rapid succession, the organism moves in one 

 direction or the other according to the direction of rotation. All varieties of spiro- 

 chetal movement are readily explained by the zone of operation of the protoplasmic 

 contraction, which may be unipolar, bipolar, median, or irregularly regional. 



The ability of Treponema pallidum to bore, corkscrew-like, through a solid medi- 

 um, is due to the extreme thinness of the protoplasmic coat and to the closeness of 

 the spirals in the firm, elastic, axial filament. T. recurrentis, which has a thicker pro- 

 toplasmic layer and fewer spirals, can penetrate a semisolid but not a solid medium. 



It is evident that in the treponemas no external flagellar apparatus is present, 

 nor is any necessary. The axial filament, however, has several characteristics in 

 common with bacterial flagella — similar morphokjgy and staining properties, similar 

 function, i.e., the function of locomotion. The similarity of the axial filament to the 

 giant involution flagella of bacteria is very striking. The only difference in these 

 two types of kinetic elements is that the bacterial flagella are extracellular or exoge- 

 nous, the axial filaments intracellular or endogenous. Their respective biological 

 properties probably determined their position in the cell. 



Leptospira. — The genus Leptospira was created because spiral organisms of this 

 type have several unique biological and morphological characteristics which distin- 

 guish them from others of the spirochete family — the extreme closeness and fineness 

 of the spirals, the typical hooking of one or both ends, the apparent absence of ter- 

 minal filaments, the indifference of the organisms to the action of concentrated 

 saponin solution and to changes in the tonicity of the medium (Leptospira is un- 

 affected either by 10 per cent sodium chloride solution or by distilled water). This 

 organism has no axial filament of the type which is so readily demonstrated in tre- 

 ponemas by treatment with bile. Recently, however, in smears of fluid cultures, 

 stained"^ by the technique for flagellum-staining, I came across some extremely deli- 



' The best way to demonstrate the terminal tilaments is by Zettnow's technique (Zettnow, E.: 

 Ztsckr.f. Hyg. ii. Infektionskrankh., 30, 93. iSgg), or a modification of it. The cultures must be freed 

 from the proteins of the medium by thorough washing (several centrifugations). Leptospiras may 

 be washed with distilled water, but for treponemas it is necessary to use 0.5 per cent sodium chloride. 

 Slides are more convenient than cover slips because as many as eight different films can be submitted 

 to identical treatment. To a drop of 2 per cent solution of osmic acid is added a drop of the spirochetal 

 suspension, with gentle mixing. The base of the mordant is a 5 per cent solution of tannic acid, to 

 100 cc. of which is added i cc. of a saturated solution of tartar emetic (Zettnow's original technique) 

 or some one of the following substances: lead acetate, zinc chloride, zinc sulphate, tin chloride, 

 aluminium chloride, colloidal iron. Lead acetate is usually easiest to obtain and gives excellent results. 

 The mixture is boiled for five minutes and filtered while hot. Ordinary alum may be used in combina- 

 tion with the tannic acid; in this case the precipitate is not filtered off but is dissoh'ed by the addition 

 of a little ammonia, followed by boiling. The air-dried film is flooded with the mordant and the slide 

 heated a few seconds, washed, then flooded with ammoniacal silver nitrate, made by adding to about 



