EFFECTS OF CARBON DIOXIDE ON PROTOPLASM. 29 



metabolism which causes the necessary changes in protoplasmic 

 consistency. L. Loeb ('20) has further suggested that a change 

 in hydrogen-ion concentration is also concerned. It will be noted 

 that carbon dioxide satisfies both of these requirements. In addi- 

 tion, the evidence presented in the present paper shows that it is 

 capable of producing exactly the sort of changes in protoplasmic 

 consistency demanded by such a theory. 



It would be easy to engage in further speculations about the 

 probable role of C(X in other physiological processes, but such 

 speculations would not be warranted by the present state of our 

 knowledge. It is suggested, however, on account of its universal 

 occurrence in cells, as well as on account of its interesting and in 

 some respects unique physiological peculiarities, that carbon diox- 

 ide should at least receive serious consideration in connection with 

 many of the as yet unsolved physiological problems which involve 

 changes in protoplasmic consistency. 



SUMMARY. 



1. A short exposure to carbon dioxide of various cells causes a 

 decrease, and a longer exposure an increase in the viscosity of 

 the protoplasm. 



2. Both of these effects are reversible, though the second one 

 tends to pass into an irreversible coagulation if the exposure is 

 sufficiently long continued. 



3. The local application of carbon dioxide to Ainteba can influ- 

 ence in a striking way the formation of pseudopodia. 



4. It is suggested that carbon dioxide may be an important factor 

 in producing many of the natural changes in protoplasmic con- 

 sistency which have hitherto been unexplained. 



LITERATURE CITED. 



Bayliss, W. M. 



'20 Colloidal Systems. IV. Reversible Gelation in Living Protoplasm. 



Proc. Roy. Soc., Vol. 916, pp. 196-200. 

 Chambers, Robert, Jr. 



'17 Microdissection Studies. II. The Cell Aster: a Reversible Gelation 



Phenomenon. Journ. Exp. Zool., Vol. 23, pp. 483-505. 

 Heilbronn, A. 



'14 Zustand des Plasmas und Reizbarkeit. Jahrb. f. wiss. Bot., Bd. 54, 

 PP- 357-390. 



