19 



solutions or suspensions in liquid air nor by a stay of short 

 duration at about - 190°. 2. Some of them are inactivated 

 by prolonged or repeated freezing at that temperature, 

 especially in very dilute solutions. 



II. MONOCELLULARS 

 SECTION I. PROTOPHYTA 



1. Bacteria and Bacterioids. The numerous investiga- 

 tions on bacteria will be classified into two groups : A. 

 Those in which the organisms were found unaffected by 

 low temperature ; B. Those describing lethal or injurious 

 effects. 



A. Many authors have reported that bacteria support 

 temperatures of 0° or of a few degrees below 0°, as used 

 in cold storage; we shall not attempt to name all these 

 investigators. 



McLean (1918) has decribed 4 species of bacteria which 

 he isolated from ice, from snow and from frozen algae of 

 the Antarctic where the mean annual temperature is about 

 -20°. 



Smart (1935) observed that some bacteria, found alive 

 in fruit held for 3 years at - 9.4°, then isolated and sub- 

 jected in pure culture to a temperature of - 8.9° for 1 

 year, produced growth at this temperature. 



Brehme (1901) reported that the cholera vibriones, in 

 bouillon cultures, survived a continuous freezing for 57 

 days at - 1° to - 16° ; nor were they killed when subjected 

 40 times alternately to - 15° and to 15°. In similar condi- 

 tions typhus bacilli survived freezing at -2° to -16° for 

 4^ months and were not killed when frozen and thawed 

 40 times at respectively -15° and 15°. 



Tanner and Wallace (1931) found that spores of 

 Clostridium hotulinum survived freezing at -16° for 14 

 months, and that commercially frozen fruits and vege- 

 tables were not sterile even after 2 years at - 16°. 



Citovicz (1928) put an emulsion of streptococci of scar- 

 let fever into capillary tubes, where they were subjected 

 to temperatures of - 17° to - 18° for at least two weeks ; the 



