DISEASES CAUSED BY SPIROCH^TES 597 



bodies stand out against the black background, and the motility of the 

 organisms may be observed. 1 



The dark-field condenser is without question the easiest method of 

 finding the Spirochseta pallida. Its use is easily learned and the appara- 

 tus is sufficiently cheap so that it lends itself to the use of the clinic and 

 the office. With very little practice it is possible to detect the spiro- 

 chaete in suspension if care is taken that not too much blood or other 

 solid particles are mixed with the preparation. Should it be impossible 

 to obtain the material scraped from syphilitic lesions in a sufficiently 

 dilute condition it is best to emulsify it in a drop or two of human 

 ascitic fluid. 



EXAMINATION IN SMEARS. The Spirochseta pallida can not be 

 stained with the weaker anilin dyes, and even more powerful dyes, such 

 as carbol-fuchsin and gentian-violet, give but a pale and unsatisfactory 

 preparation. The staining method most commonly used is the one 

 originally recommended by Schaudinn and Hoffmann. This depends 

 upon the use of Giemsa's azur-eosin stain employed in various modi- 

 fications. The most satisfactory method of applying this solution is 

 as follows: 



Make smears upon slides or cover-slips, if possible from the depth of the 

 lesions, as free as possible from blood. 



Fix in methyl alcohol for ten to twenty minutes and dry. 



Cover the preparation with a solution freshly prepared as follows: 



Distilled water 10 c.c. 



Potassium carbonate 1 : 1,000 5-10 gtt. 



Add to this: 



Giemsa's solution (fur Romanowski Farbung) 10-12 gtt. 



This staining fluid is left on for one to four hours, preferably in a moist 

 chamber. Wash in running water. Blot. 



By this method Spirochaeta pallida is stained characteristically with 

 a violet or reddish tinge. 



A rapid and convenient method for staining such smears consists in 

 the use of azur I and eosin in aqueous solutions as recommended by 

 Wood (see section on Staining, page 109). The smears are fixed in 

 methyl alcohol as before and are then flooded with the azur I solution. 

 The eosin solution is then dropped on the preparation until an iridescent 



1 For a critical summary of the various methods of dark-field illumination, the 

 reader is referred to an article by Siedentopf, Zeit. f. wiss. Mikrosc., xxv, 1908. 



