546 Journal of Agricultural Research voi. xvrri. no. 10 



Neutrai^ peptone-beef bouillon. — Growth good, better than in -f 10 

 beef bouillon. A pellicle forms. Medium greened. 



LoefFLER's solidified blood serum. — Only moderate growth and 

 a very slow liquefaction with some strains of the organism. With one 

 strain (No. 285) evidently no liquefaction. 



Potato cylinders. — Growth at first dull, yellowish white, changing 

 to a dirty, greenish brown ("Buify Citrine"). The growth is moist and 

 shining but not thick. The moister parts of the potato seem most favor- 

 able for growth. The diastatic action on the starch is moderate. 



Action on starch. — Potato cylinders on which the organism had 

 grown for three weeks or more showed a moderate change in the starch. 

 Tested with iodin the cultures gave reddish brown to purple reactions; 

 the controls gave pure deep blue. This test was performed by crushing 

 the cylinders and adding 10 cc. of water and 5 cc. saturated iodin in 40 

 per cent alcohol. 



Peptone-beef agar plus i per cent potato starch was poured into Petri 

 plates. When firm, the surface was inoculated by drawing a needle bear- 

 ing bacteria across the center of the plate. Ten days later when the 

 streaks were from 3 to 7 mm. wide the surface of the plates was flooded 

 with iodin (saturated solution in 40 per cent alcohol) . Most of the plate 

 became intensely dark blue, except along the streak of bacterial growth 

 where there appeared a clear area, or halo, from 2 to 6 mm. wide. 



Under the microscope abundant starch particles could be seen in the 

 agar, except in the halos where only a few scraps remained. A field in 

 the halo gave by count only three tiny particles, while 10 cm. out in the 

 blue agar a field of the same size gave over 200 large starch grains and 

 many more small particles. 



Plain peptone agar plus i per cent potato starch gave scantier growth 

 to the bacteria, and the test with iodin showed no trace of halos. 



Peptone-beef bouillon -f- 10 with i per cent potato starch. — Organisms 

 were grown in this medium for 12 days. Then 2 cc. of iodin (saturated 

 solution in 40 per cent alcohol) were added to the tubes. A reddish 

 brown color developed, quickly and entirely fading out, while controls 

 became and remained deep blue. Some of the same lot of cultures were 

 tested with Fehling's solution. Reactions of cultures varied from orange 

 to reddish purple; the controls were blue. After the cultures had settled 

 for some hours a very slight reddish precipitate could be discerned in 

 some of the tested tubes. 



Uschinsky's solution plus starch. — A thin starch paste was added to 

 Uschinsky's solution (about 20 cc. of starch paste to 100 cc. of the 

 Uschinsky). Cultures grown in this for three and five weeks gave, when 

 tested with iodin, brownish purple reactions. The controls were deep 

 blue. 



Milk. — Milk clears without coagulation. A watery band, rather 

 greenish in color, begins at the surface and extends downward until the 



