1062 A. F. Vass 
unsatisfactory, especially when working with frozen soils. The colonies 
on the plate may represent a single cell or a mass of cells, and, altho the 
number of colonies may be greater after freezing, the investigator is not 
at all sure that a great many of the organisms have not been killed and 
that the seeming increase is due to the breaking up of the clusters. 
TABLE 7. InFuuENcE oF Low TEMPERATURE ON BACILLUS RADICICOLA IN 
SoLuTIoN, SAND, AND Sort CULTURES 
Bacteria Bacteria per gram 
Sample Treatment per ce. 
3 of solution ana Soil 
I 2 eet SE INormalisolleeeeet a ee eee 3,000,000 | 3,700,000 | 400,000,000 
Dieres one Frozen with ice and salt at -15° C. 
Sninutes ere es eee Tae 1,400,000 | 5,200,000 | 470,000,000 
BS Meee Frozen with ice and salt at -15° C. 
TB] aVOXDU pu netaraney eras a Pl Ree AND en a Sree mar iar 1,000,000 | 3,200,000 | 500,000,000 
4.......| Frozen with ice and salt at -15° C. 
DENG UES ies) a Eh Meee pee reese ae 750,000 | 3,000,000 | 520,000,000 
SALE Frozen with ice and salt at -15° C. 
Oshours aes yh no ee 600,000 | 2,800,000 | 400,000,000 
(fete eee Frozen in liquid air at —190° C. 
Instantancoushys ser Mee see ee ae 1,000,000 | 2,700,000 | 470,000,000 
een ete Frozen in liquid air at -190° C. 
SOmmMInUtes eevee bees ete 750,000 | 2,200,000 | 380,000,000 
Big hies Frozen in liquid air at -190° C. 
US ao} Bee re Ea NAO apa ee aS 620,000 | 2,100,000 | 360,000,000 
9 Frozen in liquid air at -190° C. 
DT HOULS eats yi Cie eae ee 600,000 | 2,600,000 | 530,000,000 
10.......| Frozen in liquid air at -190° C. 
Gkhours: A544 eae ene 450,000 | 2,100,000 | 400,000,000 
In table 7 it is shown that there is a gradual decrease in the number of 
bacteria in the solution as the degree of cold and the time of freezing is 
continued. In the sand cultures there was a marked increase in the 
number of bacteria when frozen for a few minutes at -15° C. This would 
indicate a breaking up of the clusters of bacteria that may surround the 
sand particles. A shght protective action was present in the sand and 
soil cultures that was not noticed in the solution cultures. The length of 
time of freezing had very little effect when liquid air was used. In sand 
the total count was slightly below normal, and remained so during the test. 
The results obtained with the soil cultures are interesting and give 
some idea of what may be expected in such work dealing with the bacterial 
