THE STAINING OF FLAGELLA. 1 09 



If necessary, wash with absolute alcohol till only the film itself appears tinted 

 violet with the mordant. Filter a few drops of stain B on to the cover, again 

 heat till steam rises and leave in the warm stain for 2 minutes. Wash well 

 in distilled water, dry, and mount in xylol-balsam. 



3. Van ErmengeirCs Method. 



The films are prepared as above described. Three solutions are here 

 necessary : — 



Solution A. {Baiii fixateur) — 



Osraic acid, 2 per cent solution i part. 



Tannin, 10-25 P^'^ cent solution .... 2 parts. 



Place the films in this for one hour at room temperature, or heat over a 

 flame till steam rises and keep in the hot stain for five minutes. Wash with 

 distilled water, then with absolute alcohol for three to four minutes, and again 

 in distilled water, and treat with , 



Solution B. (Bain sensibilisateiir) — 



.5 per cent solution of nftrate of silver in distilled water. Allow films 

 to be in this a few seconds. Then without washing transfer to 



Solution C. {Bain reducteur et reinforqateur) — 



Gallic acid 5 grms. 



Tannin 3 » 



Fused potassium acetate 10 » 



Distilled water 350 c.c. 



Keep in this for a few seconds. Then treat again with solution B till the 

 preparation begins to turn black. Wash, dry, and mount. 



It is better, as Mervyn Gordon recommends, to leave the specimen in B 

 for two minutes and then to transfer to C for one and a half to two minutes, 

 and not to transfer again to B. It will also be found an advantage to use a 

 fresh supply of C for each preparation, a small quantity being sufficient. The 

 beginner will find the typhoid bacillus or the bacillus coli communis very suita- 

 ble organisms to stain by this method. 



Although the results obtained by this method are sometimes excellent, 

 they vary considerably. Frequently both the organisms and flagella appear 

 of abnormal thickness. This is due to the fact that the process on which the 

 method depends is a precipitation rather than a true staining. The pictures 

 on the whole are less faithful than in the first method. 



The Testing of Agglutinative and Sedimenting 

 Properties of Serum. 



By agglutination is meant the aggregation into clumps of 

 uniformly disposed bacteria in a fluid, by sedimentation the 

 formation of a deposit composed of such clumps when the 



