MARIE A. HIXRICHS. 



logical activity, as for example, the oral lobe region, is very 

 intimately dependent on its environment for the continuance of 

 its life processes. The more active such processes are, the more 

 quickly will such a region register an incompatibility in its relation 

 to its environment. Consequently, large doses of chemical or 

 physical agents will produce a gradient of death and disintegration 

 progressing from regions of high metabolic rate to those of lower 

 rate; while in the case of sublethal doses of these agents, the 

 result is an interference (temporary or permanent), with the 

 normal growth and developmental capacities of the same region, 

 the degree of interference being in general proportional to the 

 intimacy of dependence of such regions on the environment. 



As stated above, experiments in which normal eggs were 

 fertilized by sperm which had been photodynamically treated, 

 gave results of a similar kind. Since the embryo develops from a 

 zygote, the sperm component of which is responsible for the 

 bringing in of a protoplasmic system which is toxic for normal 

 development of the egg protoplasm, and which remains a part of 

 the developing embryo, there is obviously no result possible 

 other than inhibition or acclimation. And since the developing 

 embryo becomes differentially modified, it appears that the egg 

 at the time of fertilization by the injured sperm, already shows 

 evidence of the difference in susceptibility of its various parts. 



Whatever the direct effect of light on living protoplasm, 

 whether it be electron emission (Clark, '22) or heat sensitization 

 (Bovie, '13, '23), there is certainly a fundamental relationship 

 between the effectiveness of its action and the degree of physio- 

 logical activity of the protoplasm acted upon. In general, the 

 degree of physiological activity and the rate of oxygen con- 

 sumption parallel each other, and since light action requires 

 oxygen for its maintenance (under conditions of the experiment), 

 it seems likely that there is some connection between the degree 

 of effectiveness of light action and the rate at which the tissue 

 consumes oxygen. (Further experimental data are necessary for 

 the affirmation of such a premise.) 



Of the dyes used, eosin and benzoflavine are adsorbed by the 

 cell surface while neutral red and methylene blue are intra vitnm 

 dyes. Aside from their photodynamic properties, the latter t\\<> 



