214 ANIMAL AGGREGATIONS 



water and combining both liquids, these were found to carry 4.62 

 mg. of lead. The original solution was found, by similar analysis, 

 to have 1.8 mg. of lead after the death of the fishes. Adequate 

 analysis of the fishes' bodies showed no lead had penetrated. Car- 

 penter points out that the overplus of 0.21 mg. found in the analyses 

 as compared with the original solution makes the experiment incon- 

 clusive in some respects, but that it does show clearly that the fishes 

 remove toxic substances by adsorption, just as do our results with 

 colloidal silver. 



In later work (1930) Carpenter finds that the survival time of a 

 number of North American fishes is directly influenced by the value 

 of the ratio of the volume of solution to mass of individual fish so 

 long as the solution is of constant molar concentration. When the 

 concentration and volume are constant, the survival varies inversely 

 according to the mass of the fishes. For equal masses of animals, the 

 survival varies directly with the ratio of the volume of the solution 

 to the molar concentration. The results upon survival of exposing 

 groups of fishes to lethal concentrations and volumes of lead salts as 

 compared with isolated fishes, are not yet clear, but the later mem- 

 bers of a processionary series killed in the same solution survive 

 longer than do the earlier members on account of the using up of the 

 harmful agent. 



Preliminary experiments in our own laboratory in which the sur- 

 vival of groups of 10 goldfish was compared with that of the same 

 number of individuals isolated into the same volume and concentra- 

 tion of lead nitrate have revealed no significant differences when 

 solutions of from N/io to N/200 were used. The technique used 

 in these experiments differed from that of Carpenter; hence we are 

 not ready to criticize her results. But our experiments do show that 

 the group effects clearly exhibited with colloidal silver are not so 

 readily demonstrated with lead nitrate. 



Pawlow (1925) came at the same general problem from still an- 

 other angle. Led on by Ostwald's basic work on adsorption of toxic 

 salts, Pawlow worked out theoretical formulas to express the relation 

 between toxicity and adsorption on animals. These show that if 

 the active toxic substance has a direct effect upon the organism, 



