504 abstracts: bacteriology 



tion material, has a definite place in the pulp and lumber industries. 

 The inferiority of pulp containing a large amount of balsam is probably 

 not altogether due to the inferiority of the balsam wood, but to deficient 

 knowledge of how properly to manufacture it into paper. The tree 

 grows much faster throughout its entire life than spruce, but is shorter 

 lived and reaches maturity long before the latter. Virgin balsam 

 should be cut at an age of from 100 to 125 years, while spruce, as it 

 grows at present in the wild woods, should be cut at an age of from 175 

 to 200 years. The best silvicultural system of cutting is that of selection 

 cutting in small groups. Under this system the natural reproduction 

 of both spruce and balsam fir is assured, with the possibility of increasing 

 the proportion of spruce in the new stand. 



FiNDLEY Burns. 



BACTERIOLOGY. — Ability of Streptococci to survive pasteurization. 

 S. Henry Ayers and W. T. Johnson, Jr. Journal of Agricultural 

 Research, 2: 321-,330. July 15, 1914. 



The thermal death-points of 139 cultures of Streptococci isolated 

 from cow feces, from the udder and mouth of the cow, and from milk 

 and cream, showed a wide variation when heated in tubes of milk for 

 30 minutes. 



At 60°C. (140°F.), the lowest pasteurizing temperature, 89 cultures 

 or 64.03 per cent survived; at 62.8°C. (145°F.), the usual pasteurizing 

 temperature, 46 or 33.07 per cent survived; and at 71.1°C. (160°F.) 2.58 

 per cent of the cultures survived; all were destroyed at 73.9°C. (165°F.). 



The streptococci from the udder were, on the whole, less resistant 

 and those from milk and cream more resistant to heat than those from 

 the mouth of the cow and from cow feces. 



Among the 139 cultures of Streptococci there were 22 that formed 

 long chains, which, for the purposes of the paper, were considered as 

 typical Streptococci. The others were considered atypical. The typical 

 Streptococci were much less resistant to heat than were the atypical. 



This work indicates that two classes of Streptococci survive pasteuri- 

 zation: (a) Streptococci which have a low majority thermal death- 

 point, but among which a few cells are able to survive the pasteurizing 

 temperature; (b) Streptococci which have a high majority thermal 

 death-point. In the latter case the bacteria survive because the major- 

 ity thermal death-point is above the temperature used in pasteurization. 

 This ability to resist destruction by heating is a permanent characteristic 

 of certain strains of Streptococci. 



S. H. A. 



