544 



SCIENCE 



[N. S. Vol. XXXIX. No. 1006 



upon the readjustment of the soft parts of the 

 animal. 



Jaworski evolves and develops another 

 theory of phylogenetic relationship which 

 seems so untenahle that it may he disregarded 

 — namely that the strongly plicated oysters 

 such as the Ostrea edulis are the descendants 

 of the strongly plicate Gryphwas of the Meso- 

 zoic. The surface sculpture is not a funda- 

 mental character among the oysters and there 

 is no reason to search for its cause in distant 

 ancestral relationships. Regarding the phy- 

 logenetic significance of Heterostrea stein- 

 manni it would seem that it was an entirely 

 too specialized form to have given rise to the 

 subsequent Ostrea stock. 



J. A. Gardner 



Johns Hopkins University, 

 Baltimore, Md. 



SPECIAL ASTICLES 



THE CHEMICAL DYNAMICS OF LIVING PROTOPLASM 



Van't Hopf's formulation of the laws of 

 chemical dynamics has proved so stimulating 

 to various fields of chemistry that it may be 

 expected to be similarly useful if it can be ap- 

 plied to the activities of living protoplasm. 



The writer finds that by measuring the elec- 

 trical resistance of living tissues it is possible 

 to follow the progress of reactions in proto- 

 plasm in the same way that van't Hoii fol- 

 lowed the progress of reactions in vitro. It 

 therefore becomes possible to apply van't 

 Hoff's methods and formulse directly to proto- 

 plasm in its living and active condition. The 

 following example will suffice to show how this 

 may be accomplished. 



The electrical resistance of living tissue of 

 the marine alga Laminaria was measured by 

 a method which has been previously described.'^ 

 The tissue had in sea-water a resistance of 

 980 ohms.= On being placed in NaCl .52ilf 

 (which had the same conductivity as sea- 

 water) the resistance fell after 10 minutes to 

 855 ohms and after 20 minutes to 745 ohms: 

 it continued to fall rapidly and finally became 



1 Science, N. S., 35: 112, 1912. 



- If left in sea-water this resistance is main- 

 tained for a long time. 



stationary at 320 ohms. This represents the 

 death point. The total change produced by the 

 NaCl was 980-320 = 660 ohms.^ In order to 

 find out whether this change had been pro- 

 duced in such a way as to correspond to a 

 known type of chemical reaction the amount 

 of change was measured at brief intervals. 

 The results are given in Table I. 



o = total change = 980-320 = 660 ohms. 

 Temperature 18.5° C. 



According to van't HofP we can determine 

 from such measurements whether one, two or 

 more substances are taking part in the reac- 

 tion. If only one substance takes part (or 

 if two substances take part but only one of 

 them changes its concentration noticeably) 

 the reaction is said to be of the first order 

 (monomolecular) and it proceeds according to 

 the formula 



k 



1 , 



7 log 



in which t is the time which has elapsed be- 

 tween the beginning of the reaction and the 

 taking of the measurements, x is the loss in 

 3 The fact that this action of NaCl may be an- 

 tagonized by CaCl. does not affeet the subsequent 



