THE 



SCIEOTIFIC PROCEEDINGS 



OF 



THE ROYAL DUBLIN SOCIETY. 



I. 



THE EXTRACTION OF ZYMASE BY MEANS OE LIQUID AIR. 



(Preliminary Note.) 



By HENRY H. DIXON, Sc.D., F.R.S., 



University Professor of Botauy, Trinity College, Dublin ; 



AND 



W. R. G. ATKINS, M.A.,Sc.B., A.LC, 



Assistant to the Professor of Botauy, Trinity College, Dublin. 



[Read Apkil 15. PubUshed May 23, 1913.] 



Recently we found it possible to obtain the sap from various plant-organs 

 without change in concentration, by pressure after the organ was immersed 

 for a few minutes in liquid air (Dixon and Atkins, 1). It seems that the 

 exposure to the intense cold renders the protoplasm permeable, and the pressure 

 forces out the solution from the vacuoles unchanged. This suggested the 

 probability that similar exposure of the yeast-cell would render its protoplasm 

 permeable, and that the zymase and other endo-enzymes would then be free 

 to escape. Experiment has confirmed this surmise.' 



Our experiments up to the present have been made with " liquid 

 yeast," supplied to us from Guinness's Brewery, through the kindness of 

 Mr. A. McMullen. This is the top yeast skimmed off the vat after the 



' It is remarkable that Pasteur failed to extract zymase by freezing yeast (Harden, 3). 

 Probably the temperature he employed was not below the euteotic point of the cell-solutes. That 

 this point may have to be exceeded to kill a cell has been shown by Maximow (5). 



SOIENT. PEOU. K.D.S., VOL. XIV., NO. I. B 



