LABORATORY AND GREENHOUSE STUDIES. 107 



showed a tendency toward branching, this condition probably is due to the medium 

 rather than to varieties of bacteria. 



In all i)f the cultures Bacillus coli and the coconut oi'ganism be- 

 haved alike in that they grew well and reduced the color of the mala- 

 chite green. 



BEEF AGAU CONTAINING CAFFEIN. 



The use of caffein in media as a means of differentiating Bacillus 

 coli from Bacillus typhosus has been discussed, among others, by Rotli,^ 

 by Birt,^ and by Courmont and Lacomme,^ who have not, however, 

 I)resented evidence of the reliability of this means. The one point in 

 agreement among the workers is that 1 per cent, or sometimes le.ss, 

 caffein in the culture media will completely inhibit the growth of 

 Bacillus coli. Under certain conditions it is said also to inhibit 

 Bacillus typliosus, but that is of little importance here. 



Cultures were made in slant agar tubes containing 1 per cent caf- 

 fein with all the organisms used in this comparative work. After 

 eight days no sign of growth appeared on any of the slants. 



Other cultures on the same medium were made in petri dishes. 

 These were kept for several days, but gave no sign of colonies either 

 in the coconut plates or the Bacillus coli plates. 



THE MEDIA OF CAPALDI AND PROSKAUER. 



Two media,* designated Capaldi and Proskauer No. 1 and Capaldi 

 and Proskauer No. 2, are used in these experiments. 

 No. 1 is made as follows: 



Asparagin grams . . 0. 2 



Mannit do 2 



Sodium chlorid do 02 



Magnesium sulphate do 01 



Calcium chlorid do 02 



Potassium monophosphate * do 20 



Water (distilled) c. c. . 100 



No. 2 is made as follows: 



Witte's peptone grams. . 2. 



Mannit do .1 



Water (distilled) c. c. . 100 



In the first of these media, which is free from albumin. Bacillus coli 

 is said to grow well and produce acid freely. The second medium 



1 Roth, Emil. Versuche uber die Einwirkung von Kaflein auf das Bacterium typhi und coli. ZentraL 

 hlatt fiir Stoflwechsel- und Verdauungs Krankheiten, vol. 5, 1904, p. 125; Versuche iiber die Einwirkung 

 des Trimethylxanthins auf das Bacterium typhi und coli. Zentralblatt fiir Stoflwechsel- und Verdauungs 

 Krankheiten, vol. 6, January to December, 1905, p. 557. 



2 Birt, C. Caffeine Enrichment Method. British Medical Journal, October 28, 1905, pp. 1110-1111. 



3 Courmont, J., and Lacomme, L. La Caffeine en Bacteriologie. [Discusses certain distinct uses of 

 caffein as an aid in bacterial diagonsis.] Journal de Physiologie et de Pathologie Gfinerale. vol. 6, March 15, 

 1904, p p. 286-294. 



< Muir, Robert, and Ritchie, James. Manual of Bacteriology, p. 329. 



5 Potassium biphosphate, monobasic, Merck, was used by the writer in making up this medium. 



228 



