PRODUCTS OF GROWTH 399 
nary anilin dyes color the organisms readily, and they are Gram- 
negative. 
Isolation and Culture.— The members of the mucosus capsiilatiis 
group grow readily on artificial media. The colonies on agar are white 
or gray, from 1.5 to 3 mm. in diameter, very viscid, and raised; they 
tend to become confluent. When touched with a platinum needle 
the growth may be drawn away as a tenacious, sticky filament. In 
gelatin, a non-characteristic filamentous growth occurs along the line 
of inoculation and the surface becomes covered with a white, glisten- 
ing raised colony. The gelatin is not liquefied. Milk is acidified, and 
frequently the accumulation of acid leads to coagulation. A light 
pink color is imparted to litmus milk and coagulation is irregular in 
this medium. Broth is clouded, and a slimy, viscid sediment collects 
at the bottom of the tube. A majority of strains produce gas bubbles 
on potato. 
The organisms are aerobic, facultatively anaerobic. Growth takes 
place at 8° to 10° C, but 37° C. is the optimum temperature. Little 
or no growth occurs above 43° C. 
Fig. 55. — Bacillus mucosus capsulatus. X 1000. 
Products of Growth.— The majority of strains do not form indol, 
but occasional cultures give a marked reaction for this substance. ^ 
Practically all strains form a mucinous substance on artificial media. 
The reactions of fermentation have been used as a basis for separa- 
tion into types by Perkins,- who groups the organisms in the following 
manner: 
Type /.—All carbohydrates fermented with the production of gas 
H : CO2 = y) and acid; B. lactis aerogenes. 
Type //.—All carbohydrates except lactose fermented; B. mucosus 
capsulatus, B. rhinoscleromatis, B. oztenae and B. aminophilus. 
Type ///.—All carbohydrates except saccharose are fermented; 
B. acidi lactici. 
' Kendall, Day and Walker: Jour. Am. Chem. Soc, 1913, 35, 12.37. 
2 Jour. Infec. Dig., 1904, 1, 241; 1907, 4, 51; 1925, 37, 232. 
