ABSTRACTS 459 



pies from dealers or farmers in the Province of Quebec. These cul- 

 tm-es were used to test the reliability of aesculin bile-salt-agar for the 

 identification of the colon-aerogenes group. Of the 600 colonies many 

 were selected because they seemed to be slightly atypical. There 

 were only 10 exceptions; a percentage of 1.5 of all colonies tested; and 

 a percentage of 0.03 of the colonies on the plates from which the 600 

 were isolated. Seventeen of the sub-cultures were subjected to the 

 usual classification tests, and the results together with information 

 as to the source of the milk are given in tabular form. Drawings 

 showing the appearance on aesculin bile-salt-agar plates of surface 

 and deep colonies respectively are included on plates I-IV. — W. S. 



DISINFECTION 



Further Investigation into the Precipitation of the Typhoid Bacillus by 

 Means of Definite Hydrogen-ion Concentration. C. F. Kemper. 

 Jour. Infect. Diseases, 1916, 18, 209-215. 



The aim of the present work was to ascertain whether there exists 

 a specific hydrogen-ion concentration for the precipitation of all strains 

 of B. typhi. None was found; the effective range of hydrogen-ion con- 

 centration was wide, most strains being precipitated in the presence 

 of a 3.6 by 10^ hydrogen-ion concentration derived from the dissocia- 

 tion of acetic acid in the presence of sodium acetate. — P. B. H. 



Effect of Pasteurization on Mold Spores. Charles Thom. J. Agr. 



Res., 1916, 6, 153-166. 



The object of this investigation was to see whether mold spores 

 could resist the heat applied in pasteurization. Several species of 

 Aspergillus and Mucor, and a large number of species of Penicillium 

 together with a few other kinds of molds were tested. It was found 

 that nearly all the mold spores were killed either by the holder process 

 (30 minutes at 63°C.) or by the flash process (30 seconds at 74° or 80°C). 

 The flash process at 74°C. proved the most efficient, only occasional 

 spores surviving. 



The effect of dry heat was also investigated. Dried preparations 

 of the spores were submitted to various degrees of temperature. The 

 resistance to dry heat was found to be much greater than to moist heat, 

 considerable numbers of the spores surviving unless temperatures of 

 120°C. (for 30 seconds) were used.— H. J. C. 



The Physical Chemistry of Disinfection. J. F. Norton and Paul H. 



Hsu. Jour. Infect. Diseases, 1916, 18, 180-194. 



This contribution attempts to apply physico-chemical methods 

 to the problem of the mechanism of disinfection; and in the first place 

 to demonstrate the roles which undissociated acids, hydrogen ions and 

 anions play in the process. The first test was made with formic acid, 

 using B. typhi as the test organism. The results seemed to justify the 

 following conclusions : that acids act as disinfectants through the agency 

 of the hj^drogen ions, and that the disinfecting power is proportional 



