196 



SCIENCE 



[N. S. Vol. XLII. No. 1075 



The terms " toxic " and " poisonous," as 

 used popularly in characterizing chemical sub- 

 stances, are subject to still another considera- 

 tion. Substances like corrosive sublimate, 

 copper salts, hydrochloric acid and phenol, are 

 popularly called " toxic " substances because, 

 in concentrations familiarly used, they pro- 

 duce such marked chemical reactions in organ- 

 isms as to cause serious impairment of func- 

 tion and perhaps death. It should be borne in 

 mind, however, that these substances lose their 

 abUity to act toxically on sufficient dilution, 

 and even the so-called harmless chemical 

 agents when sufficiently concentrated, if still 

 soluble, become harmful. The question of 

 toxic action, therefore, comes down finally not 

 only to a matter of the chemical properties of 

 substances, but equally to a question of the con- 

 centration of the solution in which they en- 

 counter the organism. It would follow that 

 perhaps all substances acting singly are poten- 

 tially toxic. 



It might seem that water, at least, would 

 escape the suspicion of being " poisonous." Of 

 course, pure water is practically unknown to 

 biology and little can be asserted concerning 

 its action on organisms. When this substance 

 is referred to, distilled water, a dilute solution 

 of various substances, is usually meant. The 

 work of a host of investigators on distilled 

 water has led to a great variety of results, a 

 fact due on the one hand, doubtless, to the 

 great variation in the water used, and, on the 

 other, to the varying susceptibility of the ex- 

 perimental organisms employed. It has, how- 

 ever, been repeatedly shown that very minute 

 traces of salts are able to profoundly modify 

 the physiological properties characteristic of 

 highly purified water. 



It has been shown that distilled water with- 

 draws small quantities of electrolytes from 

 various organisms of both plant and animal 

 origin, with the result that as this process ad- 

 vances, the water becomes an increasingly con- 

 centrated solution of ions. The ability of 

 Fundulus eggs to resist the action character- 

 istic of water rendered in a scientific sense 

 even approximately pure, as claimed by Loeb, 



seems to be very unusual. It would be of in- 

 terest to know accurately what the ion concen- 

 tration of the distilled water used in these in- 

 vestigations might have been at the beginning 

 of the experiment and after it had been occu- 

 pied by the Fundulus eggs. 



If toxicity is indicated by functional de- 

 rangement due to chemical reactions, then 

 clearly nothing can be toxic in its action that 

 can not produce chemical change in the organ- 

 ism. In other words, mere absence can not 

 furnish a ground for charges of toxicity 

 against any substance. If the solution from 

 which a necessary substance is lacking causes 

 the development of toxic properties (i. e., func- 

 tional derangement due to chemical modifica- 

 tions produced in the organism by the external 

 medium) the reaction causing the derange- 

 ment must proceed from the substances in posi- 

 tion to afi'ect the organism. Hence, incom- 

 plete nutrient media or unbalanced solutions, 

 both producing functional derangement, bring 

 about this effect through the reactions per- 

 formed by the substances present, certainly not 

 by those not present. Perhaps the most satis- 

 factory approach to the situation is seen through 

 the relation supposed by Loeb and others to 

 exist between ions and proteins in the living 

 organism. For normal functioning certain 

 affinities in the proteins of the organism must 

 be occupied by certain ions in a rather definite 

 way. When one such ion is lacking to the 

 medium, the affinities normally occupied by 

 it are satisfied in a chemical way by ions pres- 

 ent without, however, satisfying the corre- 

 sponding physiological requirement. While, 

 therefore, the absence of a necessary ion gives 

 the opportunity for the harm-bringing re- 

 action to take place, the actual damage is 

 wrought within the ceU by constituents actu- 

 ally there present. Thus, a medium char- 

 acterized as deficient or unbalanced becomes 

 actively injurious through the effects produced 

 by the ions that are present, and malnutrition, 

 starvation, or even a more violent type of 

 chemical injury may appear. 



EoDNET H. True 



Bureau of Plant Industry, 

 IT. s. Department op Agriculture 



