Fat in Micro-organisms 



513 



on fine linen, dried at 37° for two days, ground in a mortar until 

 it would pass a 60 mesh sieve, and divided into four portions. 

 The first was dried at 100° to constant weight which was 45.7 

 per cent, of its original weight. The second, without prelimi- 

 nary treatment was extracted in a soxhlet with ether then with 

 alcohol, and again with ether. The ether extract of the alcohol 

 extract was added to the other ether extracts and dried. The 

 result was 7.48 per cent, of the original dry weight of the pow- 

 dered mycellium. The third portion treated by the alcoholic 

 ammonia method, gave 8.45 per cent. ; the fourth portion treated 

 by the HC1 method gave 10.13 per cent. An aliquot part of 

 this last sample, which was not dried, but was saponified with 

 alcoholic potash yielded 38.7 per cent unsaponifiable matter. 



253 (2213) 

 Some observations on pellicle formation. 

 By A. G. BENTON. 



[From the Department of Bacteriology, University of Minnesota, 

 Minneapolis, Minn.] 



Bacillus subtilis characteristically produces a diffuse turbidity 

 on broth, which usually clears toward the end of the first twelve 

 hours, the organisms floating cn the surface in small islands. 

 These later grow together producing a heavy wrinkled pellicle. 

 It seemed therefore that a study of possible factors influencing 

 this spontaneous migration to the surface might illuminate the 

 subject of pellicle-formation and surface growth in general. 



Equal amounts of a young diffuse culture of B. subtilis were 

 introduced into tubes containing each 10 c.c. of ordinary broth. 

 These were incubated and at hourly intervals for 36 hours ob- 

 servations were made of morphology, progress of growth, spore 

 formation, buoyancy of the pellicle and surface tension of the 

 medium. The surface patches appeared at 10 hours, and the 

 pellicles were well formed at 15. The first positive heat test for 

 spores was obtained at 20 hours, but the cultures were not con- 



