428 



Scientific Proceedings, Royal Dublin Society. 



from the untreated tissues is seldom at all similar to the concentration of that 

 obtained from the same tissues after freezing. It is hard to see how freezing 

 could be supposed to alter the concentration of the sap, whereas, as we have 

 already seen, it is certain that the sap pressed from living tissues may be 

 considerably less concentrated than that which remains behind, and conse- 

 quently less concentrated than that which was originally in the cells of the 

 tissue before the pressure was applied. 



It is well known that chemical changes are arrested at such low 

 temperatures as that of liquid air; however, it seemed just possible that 

 changes might take. place in the proteids or in the protoplasm just as the cold 

 was being applied, and that these changes might lead to an increase in the 

 quantities of dissolved substances in the sap. 



To set this doubt at rest we determined the freezing-points of the sap 

 pressed from the untreated roots of Beta vulgaris and from the leaves (also 

 untreated) of Chamaerops hmnilis before and after freezing in liquid air ; also 

 of the fluids of an &gg and of bull's blood under the same conditions. These 

 liquids were not cleared in any way of the matter suspended in them, so it is 

 certain that they contained ample amounts of proteids and of protoplasm to 

 test the point. The results were as follows : — 



In no case was a greater depression detected after exposure to liquid air. 

 The diminution in the depression observed in the experiments 553 and 482 

 appears to be due to tlie expulsion of dissolved gases. The frothing of the 

 sap of Chamaerops on thawing after treatment with liquid air was very 

 marked. This was not looked for in the case of the bull's blood. 



Hence it appears that there is no reason to believe that the application of 

 liquid air leads to a concentration in solutions in contact with proteids and 

 protoplasm. 



Again, the sap extracted from plant-organs after exposure to liquid air 

 does not cause plasmolysis of the cells in these organs. This was demonstrated 



