﻿446 ASHBTJRN AND CRAIG. 



those in the wet preparations, if the spring be subjected to forces anal- 

 ogous to those acting on the treponema during the making and drying 

 of the smear. 



The stained forms, presenting many variations as to size and shape, 

 may be most conveniently described by dividing them into types or 

 classes. While the length and number of curves vary greatly, the exam- 

 ination of a large number of Treponema pertenuis shows the average 

 number of curves to be about eight. Seventeen is the greatest number 

 counted on one organism, two the smallest. Many individuals show 

 only four or five turns, only a few have more than twelve. All types, 

 shapes and sizes stain with difficult}', showing best with Giemsa's stain, 

 which gives them a pinkish-violet color. 



Type A (see PI. IV) is probably the most common stained type of 

 'Treponema pertenuis , as it is of Treponema pallidum. This may be said 

 to be the classical type of the latter, but the other forms to be described 

 for pertenuis may also be found for it. 



This type is usually straight, or but slightly bent; it shows regular and 

 even curves which are very fine, and terminates in narrow pointed ends 

 which have been interpreted as flagella. It stains evenly throughout, 

 although the finely pointed ends show less distinctly than the main part, 

 probably because of their size. 



Type B is likewise very common, and differs from A in having a 

 straight and usually thin portion in some part of its course, frequently 

 near the middle. This appearance has been variously interpreted by 

 different observers; principally as a union of two organisms by their 

 flagella in beginning agglutination, as an incomplete separation of indi- 

 viduals resulting from longitudinal division, or as beginning or incom- 

 plete transverse division. 



A spiral wire spring may be made to present a similar appearance if 

 one or more of its coils is straightened out by traction and pressure. 



Type C corresponds most closely with that we consider the unaltered 

 form as seen in wet preparations. It corresponds to type A except 

 that instead of terminating in finely pointed ends, it shows a dot or little 

 knob at one end or often one at each end. This is the appearance seen 

 almost uniformly in wet preparations and we think that it is due to a 

 tight curling of the ends, such as is -seen on the shoots of many young- 

 plants. This curl may straighten out under the influence of age or 

 drying, and the end may then appear as a finely attenuated point or 

 flagellum. 



Type D is also common and differs from A and C in that one or both 

 ends, instead of showing a finely attenuated point or blunt dot, show a 

 ring. 



This ring frequently appears thicker and heavier than the main part of 

 the body. With the spiral wire we may obtain a similar picture if we 



