CHAPTER XII 

 PROTECTION FROM TOXIC REAGENTS 



Shortly after the pubUcation of the preliminary announcement 

 which the preceding chapter restates, Bohn and Drzewina (1920) 

 published the first of a brilhant series of studies, apparently not yet 

 concluded, which opened for investigation another phase of the 

 subject that has yielded much evidence concerning the possible 

 survival value of groups of animals for the individuals composing 

 the groups. The general results obtained may be summarized in 

 their own words (1926): 



"Nous avons recherche I'intervention du facteur masse dans les 

 reponses de divers organismes vis-a-vis de multiples agents nocifs 

 du milieu exterieur. Dans une masse M d'eau, on introduit une 

 masse m d'un etre vivant {m etant egal ou inferieur a M/ioo), 

 cette masse resiste a un agent nocif determine (substance chimique, 

 par exemple); mais une masse plus petite, m/10 ou m/ioo, ne 

 resiste pas; tout se passe comme si la masse de matiere vivante 

 exergait, vis-a-vis d'elle-meme, un eft'et protecteur (auto-protec- 

 tion)." 



MASS PROTECTION FROM COLLOIDAL SILVER 



Drzewina and Bohn worked with colloids of the heavy metals, 



particularly with colloidal silver. We have spent much time in this 



laboratory, also,' studying mass relations of animals when exposed 



to colloidal silver;' and if the following report and discussion is 



' The stock suspension of colloidal silver was made as follows, from directions fur- 

 nished by Dr. Terry-McCoy of the Department of Chemistry of the University of 

 Chicago: Dissolve 4 grams of commercial dextrine in 100 cc. of water and then 4 grams 

 of pure caustic soda. Dissolve 3 grams of silver nitrate in 20 cc. of water and add to the 

 dextrine-soda solution. The precipitate of silver oxide that is formed is gradually re- 

 duced by the dextrine, the color changing to reddish brown. After 20-30 minutes, add 

 100 cc. of 90 per cent alcohol and stir. Allow the mixture to settle for 15-20 minutes, 

 and then pour off the liquid from the particles of silver at the bottom. Add about 200 

 cc. of water and the silver particles will generally disperse; however, if this is not the 

 case, shake or stir until an even suspension of silver results. 



