Apeii, 8, 1910] 



SCIENCE 



551 



time, becoming more and more parallel to the 

 base line. If we are dealing with changes caused 

 by microorganisms, the active mass is increasing 

 as long as microorganisms increase, and conse- 

 quently the velocity of the process, or the angle 

 of elevation, will rise as long as the increase con- 

 tinues. This elevation of the curve is character- 

 istic for compounds produced by any multiplying 

 organism. From the time the increase ceases, we 

 are dealing with a purely enzymatic curve. 



The exact plotting of the curve allows us to 

 make fairly accurate statements about the miil- 

 tiplication and the duration of the increase of 

 bacteria, even if they can not be coujited by our 

 present methods. The point of inflection of a 

 curve shows the moment when the organisms 

 producing the substance under study reach their 

 maximum number and can be studied with the 

 greatest convenience. 



In some instances, the point of inflection is 

 changed to a straight line, indicating a very re- 

 sistant strain of bacteria; this seems to take 

 place especially in poor media, as soil extracts. 

 A few experiments indicate that poorly nourished 

 bacteria are able to produce a larger amount of 

 fermentation products than well-nourished bac- 

 teria, though they need a much longer time to 

 accomplish it. 

 The Society Card as a Basis for Classifying the 



Bacteria producing Soft Rot in Vegetables: 



H. A. Habding and W. J. Mobse, New York 



Agricultural Experiment Station. 



This group includes B. carotovorus Jones, B. 

 aroidew Townsend, B. omnivorus van Hall, B. 

 oleracecB Harrison and some other described 

 forms. 



A comparison on the basis of the society card 

 brings out the fact that these described cultures 

 are identical in all cultural characters except the 

 results from the fermentation tube. 



Extended study of this point indicates that this 

 difference is more apparent than real, since the 

 normal gas-forming ability of this group lies so 

 near the amount required to saturate the fer- 

 mentation tube that the appearance of visible gas 

 varies with the fermentative vigor of the par- 

 ticular culture. 



These results indicate that in cases where the 

 fermentative ability of a culture is weak there 

 is need of a more accurate instrument than the 

 fermentation tube for accurately detecting gas 

 formation. 



(Data to appear as New York Agricultural 

 Experiment Station Technical Bulletin 11, 1909.) 



Does the Group Number on the Society Card 



Carry the Classification far enough to Break 



up the Species? H. A. Harding, New York 



Agricultural Experiment Station. 



This point was tested with approximately fifty 

 strains of P. campestris (Pam.) Smith. This 

 species was chosen because it is a well-known, 

 chromogenic, plant-pathogen in which the limits 

 of the species can be determined with the mini- 

 mum chance of error. 



Some of the tested strains were freshly isolated 

 from the host while others had been cultivated in 

 various laboratories for many months. The larger 

 part of these cultures were revivified just previous 

 to being tested and were tested on standard media. 

 In some cases these precautions were purposely 

 omitted. Independent observations were made in 

 some cases by three different workers and media 

 prepared by three different persons was used. 



With the exception of the reduction of nitrate 

 there was no variation, in the group number as 

 determined from these cultures. 



The variation in nitrate reduction, as deter- 

 mined by the oflBcial method for nitrite, was 

 apparent rather than real since it was not shown 

 by the nitrite test with the starch, KI, H,SO» 

 test. The faint reactions obtained with the oflBcial 

 test were undoubtedly due to absorbed nitrite. 

 Nitrite is not absorbed equally by all tubes and 

 a large number of check tubes must be held to 

 insure accurate comparisons in faint reactions. 



A New and Improved Method of Enumerating 



Air Bacteria: Leo F. Eettgeb, Yale University. 

 Studies on Bacterial Mutation: Leo F. Eettgeb, 



Yale University. 

 A Comparative Study of Intestinal Streptococci 



from the Horse, the Cow and Man: C.-E. A. 



WiNSLOw and G. T. Palmeb, Massachusetts 



Institute of Technology. 



Andrewes and Herder's statistical study of the 

 streptococci has for the first time made it possible 

 to classify the principal types of this complex 

 group in a tairly satisfactory manner. One of the 

 most interesting points about Andrewes and Her- 

 der's classification, and the earlier observations 

 of Gordon and Houston on which it was founded, 

 was the apparent difference between streptococci 

 from the intestines of the horse, the cow and man. 

 In the present investigation we have tested this 

 point by isolating one hundred strains of strep- 

 tococci from faeces of each of the three animals; 

 we have cultivated them in broth containing four 

 different fermentable media (dextrose, lactose. 



