Staining 421 



therefore their probable cause. The observations of Schau- 

 dinn and Hoffmann, quickly confirmed by Metschnikoff,* 

 have now been universally accepted. 



Morphology. The organism is a slender, flexible spiral, 

 usually showing from eight to ten undulations, but occa- 

 sionally being so short as to show only two or three, or so 

 long as to show as many as twenty. 



It is very slender, measuring from 0.33-0.5 /* in breadth 

 to 3.5-15.5 V- in length (Levaditi and Mclntosh). 



It forms no spores. Multiplication takes place by trans- 

 verse division. 



It is motile, and when observed alive by a dark field 

 illuminator, can be seen to rotate slowly about its longitu- 

 dinal axis at the same time that it slowly sways from side 

 to side with a serpentine movement. The organisms are 

 provided with flagella. Usually there is one at one end, 

 but sometimes one at each end. 



Staining. The original discovery of the organism was 

 achieved through the employment of Giemsa's stain a 

 modification, of the Romanowsky method. But by this 

 method the organisms appeared very pale and not very 

 numerous. Goldhornf improved the method as follows: 



In 200 c.c. of water, 2 grams of lithium carbonate are dissolved and 

 2 grams of Merck's medicinal, Griibler's BX, or Koch's rectified methy- 

 lene-blue added. This mixture is heated moderately in a rice boiler 

 until a rich polychrome has formed. To determine this a sample is 

 examined in a test-tube every few minutes by holding it against an 

 artificial light. As soon as a distinctly red color is obtained, the desired 

 degree of heating has been reached. After cooling it is filtered through 

 cotton in a funnel. To one-half of this polychrome solution 5 per cent, 

 of acetic acid is gradually added until a strip of litmus-paper shows 

 above the line of demarkation a distinct acid reaction, when the re- 

 maining half of the solution is added, so as to carry the reaction back 

 to a low degree of alkalinity. A weak eosin solution is now prepared, 

 approximately 0.5 per cent. French eosin, and this is added gradually 

 while the mixture is being stirred until a filtered sample shows the filtrate 

 to be of a pale bluish color with a slight fluorescence. The mixture 

 is allowed to stand for one day and then filtered. The precipitate 

 which has separated is collected on a double piece of filter-paper and 

 dried at room temperature (heating spoils it). When completely 

 dried it can easily be removed from the paper and may then be dissolved 

 without further washing in commercial (not pure) wood alcohol. The 

 solution should be allowed to stand a day, then filtered. The strength 

 of this alcoholic solution is approximately i per cent. To use the stain, 

 one drops upon an unfixed spread enough dye to cover it, permits it 

 to act for three or four seconds, and then pours it off and introduces the 

 glass slowly, spread side down, into clean water, where it is held for 



* " Bull. Acad. de med. de Paris," May 16, 1905. 

 f "Jour. Exp. Med.," viii, 1906, p. 451. 



