8 THE AMERICAN MONTHLY [January, 



are observed. I have obtained my best results with a culture about 

 two days old. The surface of agar seems preferable to gelatine for cul- 

 tivating bacteria for this purpose. 



In testing the various methods and their modifications I have stained 

 the tlagella on a considerable number of bacteria, among which I will 

 mention a large motile bacillus quite common in Potomac water, the 

 Bacilhis fluorescens liqziefaciens^ and the Bacillus coli comtniinis. 

 The last of these, like the Typhoid bacillus^ is provided with rings of 

 flagella, and consequently belongs to the Peritricha. The flagella on 

 each of these species have been stained by the use of both an alkaline 

 and an acid mordant. 



Although a large amount of work has been done to develop satisfac- 

 tory methods for staining the flagella on motile bacteria, there seem to 

 be many conditions that are not yet fully understood. These must be 

 carefully worked out by actual experiment before we will be able to 

 determine accurately the specific character of the flagella on the different 

 species of bacteria. 



No flagella have been found on the swine plague and other non-motile 

 bacteria, although a very large number of specimens have been stained 

 by the same methods that I have successfully employed with the motile 

 forms. This, together with the fact that with certain motile bacteria 

 at least a few flagella can be seen in every stained preparation, elimi- 

 nates from the writer's mind the doubt that has occasionally been ex- 

 pressed, that the long wavy or spiral filaments seen to radiate from the 

 bacteria or lying between them do not belong to the germs with which 

 they are associated. 



I am indebted to Dr. Theobald Smith for suggestions whicli he lias 

 offered from time to time during the prosecution of this work. 



Bibliography. 



I. Cohn,F. Untersuchungen liber Bacterien. Beitrlige zur Biologic der Pflan- 



ze?t. Bd. I (1872), p. 126. 

 3. Dallinger, W. H., and Drysdale, y. jf. On the existence of Flagella in 



Bacterium Termo. 77/e Monthly Microscopical 'Journal (London). 



Vol. xiv ^1875), p. 105. 



3. Dallinger, W. //. On the Measurement of the Diameter of the Flagella 



of Bacterium Termo. Jour, of the Royal Mic. Society. Vol. i (1878), 

 p. 169. 



4. Koch, Robert. Untersuchungen aber Bacterien. Beitriige zur Biologic der 



Pflanzeu. Bd. II (1877), P- 4i6. 



5. Neuhaiiss, R. Ueber die Gisselen an den Racillen der Asiatischen Ciiolera. 



Centralblatt f. Bakteriologie u. Parasitcnkinide. Bd. \^ (18S9), p. 81. 



6. Locffier, F. Ein neue Methode zum Farben der Mikro-organismen im be- 



sonderen ihren Wimperhare und Geisseln. Ibid. Bd. VI (1SS9), p. 

 209. 



7. Locffier, F. Weitere Untersuchungen uber die Beizung und Farbung der 



Geisseln bei den Bakterien. Ibid. Bd. VII (1890), p. 625. 



8. Trenkmami, Dr. Die Farbung der Geisseln von Spirillen und Bacillen. 



Ibid. Bd. VI C1889), p. 433. 

 8. Trcnhniann, Dr. Die Farbung der Geisseln von Spirillen und Bacillen. 

 Ibid. Bd. VIII (1890), p. 385. 



10. Dozudcszuell, G. F. Note sur les Flagella der microbe der Choli'ra. An- 



)iiilc^ dc Micrographie. T. II (1890), p. 367. 



11. Smith. Theobald. Einige Bemerkungcn Uber Siiure und Aikalibildung bei 



Bakterien. Centralblatt f. Bakteriologie n. Parasitenknnde. I?d. VIII 

 (1890), p. 389. 



12. Moore, V. A. A review of the methods of Demonstrating the Flagella on 



