88 PKELIMINAKY COLD STOKAGE STUDIES. 



zero. Conradi and Vogt rt have found that B. proteus fluoresceins 

 will grow at zero, and B. Fischer 6 found a pus-forming coma bacillus 

 which nourishes at this temperature. 



INHIBITORY ACTION OF LOW TEMPERATURES ON BACTERIA. 



' The reverse of the question of life and reproduction at low tempera- 

 tures may be found in those investigations dealing with the destruc- 

 tion or inhibition of bacteria by cold. Repeated attempts to induce 

 certain pathogenic organisms to grow at temperatures even somewhat 

 above zero have failed, as did those of Brehme, c who worked on chol- 

 era and typhoid, and of Dieudonne/ who sought through successive 

 lowering of the temperature by 5° stages to cultivate an anthrax bacil- 

 lus resistant to cold; +10° C, however, was the limit of growth for 

 this organism. 



In relation to the self-purification of ice from bacteria Prudden e was 

 one of the earliest workers. He concluded that 51 days were suffi- 

 cient to kill B. prodigiosus; Stap. pyogenes aureus was reduced to 

 one-fifth of its original number in 66 days, and B. typhosus was greatly 

 reduced in 103 days. Alternate freezing and thawing is more effective 

 as a killing agent than a single freezing of longer duration. Prudden 

 states that the act of freezing itself either kills or reduces vitality, 

 an opinion in which other investigators, Macfayden, for example, do 

 not concur. Undoubtedly, however, according to the work of Sedg- 

 wick and Winslow/ continued effects of freezing temperatures, at 

 least so far as organisms in water are concerned, tend to greatly 

 reduce their numbers or even to kill them outright. These authors, 

 however, lay particular stress on the time factor, believing that ice 

 from polluted streams should be stored for months to permit the cold 

 to thoroughly act on the organisms present. 



Smith and Swingle ^ believe that the effect of very low temperatures 

 is overestimated and that the cold produced by ice and salt mixture, 

 about — 17° C, is as efficacious as liquid air. They hold that the 

 critical point for the generality of organisms lies at or near 0° C, but 



«Ein Beitrag zur Atiologie der Weil'schen Krankheit, Zts. Hyg. Infekt., 30: 287. 



& Deutsche med. Woch., 1893, No. 25. 



c Uber die Widerstandsfahigkeit der Cholera Vibrionen und Typhusbacillen gegen 

 niedere Temperaturen, Archiv. Hyg., 40: 320. 



dBeitrage zur Kenntnis der Anpassungsfahigkeit der Bakterien an urspriinglich 

 ungunstige Temperaturverhaltnisse, Arb. aus dem Kaiserl. Gesundheitsamte, 9:492. 



e Bacteria in Ice and their Relations to Disease, with Special Reference to the Ice 

 Supply of New York City, Medical Record, 1887, 31: 341. 



/Experiments on the Effect of Freezing and Other Low Temperatures upon the 

 Vitality of the Bacillus of Typhoid Fever, with Considerations Regarding Ice as a 

 Vehicle of Infectious Disease, Mem. Amer. Acad. Arts and Sci., 1902, 12 (5). 



yDer Einfluss des Gefrieren auf Bakterien, Zentrbl. Bakt., I Abt. Ref., 1905-6, 

 37: 357. 



