BY R. GREIG-SMITH. 147 



seeded with soil-organisms and incubated for some days, when a 

 suspension of the test-organism, Bac. prodiyiosus, was added to 

 the capsule. After incubation at 22° for a day or two, the cells 

 were distributed, either by blowing air through the culture or 

 by repeatedly drawing up and blowing out the liquid in a pipette. 

 Then 1 c.c. was abstracted, and a count of the bacteria made. 

 Previous to the mixing, the height of the liquid on the paper- 

 scale was read, and afterwards the volume was determined by 

 water run from a burette to the same mark. 



The soil-organisms were obtained from a garden-soil that had 

 been kept some time in the laboratory. The numbers of bacteria, 

 originally high, as the soil had been heated, had fallen to that 

 normal for the soil, viz., to 6 to 8 millions per gram. Plates of 

 Lipman-Brown agar were smeared with the soil-suspension in 

 appropriate dilution, and, after several days, it was noted that 

 the flora consisted roughly of 30% of bacteria, and 70% of Actino- 

 myces-forms. Of the latter, 17% were Actino. chromogena^ which 

 darkened nutrient agar strongly; and 23% were Actino. odorifera, 

 which darkened the agar slightly; the remaining 30% were 

 indefinite. Many colonies were picked from the plates, the 

 micro-organisms were classified or grouped, and representatives 

 of the groups used for infecting the liquid outside the collodion- 

 capsules in the tubes. 



The experimental results were noted as the progeny of one 

 test bacterial cell originally added to the collodion-capsule, but 

 as nothing will be gained by giving the exact numbers, the 

 general indications, as compared with control-tests obtained from 

 the figures in the various experiments, are here noted. 



Experiment ii. Soil-extract [soil 1, water 2 parts]. 



Soil-bacteria, 6 days at 18°; test-bacteria, 1 and 7 days at 22". 

 Inhibiting strongly — Rhizobium from soil, Bac.A7. 

 Inhibiting slightly — Various (5) Actinomyces-forms, Bac. A5. 

 Accelerating slightly — Aspergillus sp., Bac. A2, 

 Accelerating strongly — Bac. Al. 



A.S an indication of the value of the terms, it may be said 



