k; 



Ac'cordiiiji," to H('i)l)iii'ii and IJazzoiii (li)!.")), oxidase 

 was still active aftci' an cxposui-c of 3Vii hours to tlie 

 tompcratiire of li(iiiid air, wliile an aqueous solution of 

 urease rotaincd 96.29% of its initial activity after having 

 been kei)t in liquid air for 100 hours. 



Bickel (1905) subjected pepsin (in i>astric juice) to 

 liciuid air temperatures for 22 hours, after which treatment 

 the proteolytic activity of the pepsin was not impaired. 

 Nor did repeated freezing in liquid air and thawing (up 

 to 6 times witliin an hour) produce any effect. 



Solutions of injps'ni contained in glass tubes and frozen 

 in liquid air, then thawed rapidly in tap water, and re- 

 frozen in the same manner 12 times, showed 70% of the 

 trypsin inactivated when the 5% stock solution was diluted 

 1-500, and 17% when it was diluted 1-10 (Rivers, 1927). 



Galvialo (1937) subjected catalase from human blood 

 and diastase from saliva (either undiluted or diluted with 

 water) to litpiid air temperatures; the catalase was not 

 affected, but the activity of the diastase was reduced to 

 one half. 



The literature on the action of low temperature on 

 enzymes, up to 1913, has been reviewed by Hepburn 

 (1915). 



3, Enzy molds. According to Tetsuda (1912), sera 

 frozen in an ice chest, for times varying from a few hours 

 to several weeks, and either kept continuously in the 

 frozen state or frozen and thawed repeatedly, did not show 

 any alteration of complement, of agglutliiui, of Jtemoli/slu, 

 of precipitin, or of the properties of inducing and of at- 

 tenuating anaphylaxis. (Freezing was used as a method 

 of concentrating these various substances in the sera.) 



The toxin of Clostridium hotidluum showed no decrease 

 in toxicity after having been stored at -79° for 2 months 

 or at -16° for 14 months (Tanner and Wallace, 1931). 



CompJement, frozen 12 consecutive times, in undiluted 

 guinea pig serum, or in 1-10 dilutions, was not affected; 

 l)ut it was inactivated when frozen the same number of 



