EXPERIMENT STATION BULLETINS. 391 



MICRO-ORGANISMS. 



Table VIII gives the counts and species of micro-organisms found in 

 butter. Column a is the fresh butter; columns a,, b, c, and d, the four 

 different cold storages in November, and columns a^, e, f, and g, the same 

 storages in February. The numbers are average numbers from the three 

 different dilutions (see p. 10). In some cases the numbers in the different 

 dilutions were so contradictory that the organisms may not have belonged 

 to the original butter sample, being merely contaminations. In these cases 

 we did not give the number but simply stated their presence by a ( — ) sign. 



THE BACTERIA. 



All micro-organisms in our work were isolated in the same way. The 

 agar plates were first counted and then the different colonies were isolated 

 into broth; from this, gelatin plates were made as soon as the broth culture 

 was grown, usually after 1 or 2 days. From this gelatin plate the descrip- 

 tion of the gelatin colonies was taken, and the micro-organisms, isolated on 

 slant agar. The two days old agar streak was used for the morphology. 

 From this culture transfers were made into gelatin, broth and litmus milk; 

 most cultures were grown in litmus milk at 20 and 37°. Some were also 

 transferred on potatoes. The broth culture was used for the inoculation 

 of the fermentation tubes containing dextrose, lactose and saccharose in 

 sugar-free broth. 



After we were through with all examinations we tried to identify the bac- 

 teria as far as possible. We separated them first according to their mor 

 phology into Cocci, Bacteria (non-motile rods). Bacilli (motiie rods). Strep- 

 iothrix (this may belong to some other group; we cou.d not find a suitable 

 description and classification of this type of micro-organism, and therefore 

 we used the same name that was used by Reinmann and Jensen), Yeasts 

 (all of them non-spore-producing), and Molds. The groups of bacteria 

 were subdivided into liquefying and non-liquefying, and acid and non-acid 

 in dextrose broth; this classification according to the physiological properties 

 seeming very valuable to us, since the physiological actions, only, have an 

 influence upon the decomposition of butter. Esten, in his latest publica- 

 tion, "Sources of Bacteria in Milk," uses a similar classification. 



When we came to the identification of the bacteria, we found that the 

 descriptions of bacteria in Migula's System der Bacterien and in Chester's 

 Manual of Determinative Bacteriology were so incomplete and paid so little 

 attention to the physiological changes that we did not dare to use these 

 names for our bacteria. Thus the "Classification of Dairy Bacteria," by 

 Conn, Esten and Stocking was the only classification that enabled us to 

 identify the greater part of our organisms. This work refers only to bac- 

 teria which are found in milk and milk products, and its use therefore is 

 limited, but the method of description makes it really possible to compare 

 and identify bacteria, whereas in using the other works with their scanty 



