Vol. LIII. November, 1927. No. 5. 



BIOLOGICAL BULLETIN 





STUDIES IX ANIMAL AGGREGATIONS: THE RELA- 

 TION BETWEEN MASS OF ANIMALS AXD RE- 

 SISTANCE T< ) COLLOIDAL SILVER. 



\V. C. ALLEE. 



THK I'NIYERSITY OF CHICAGO. 

 AND 



J. F. SCHUETT, 

 THE UNIVERSITY OF NEBRASKA. 



< >ne of us has been interested for many years in studying the 

 causes and effects, particularly the physiological effects, of close 

 aggregation upon animals. Much of the literature dealing with 

 this problem has been surveyed elsewhere (Alice, 1927). The 

 work on which the present paper is based was stimulated by the 

 repeated reports of Drzewina and Bonn (1921-1926) of which 

 the general results can best be summarized in their own words 

 (1926): 



' Nous avons recherche 1'intervention du facteur iinissc 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 in d'un etre vivant (-in etant egal ou inferieur a M/IOO), 

 cette masse resiste a un agent nocif determine (substance chimique 

 par exemple) ; mais une masse plus petite, in/io ou w/ioo, ne re- 

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

 exerqait, vis-a-vis d'elle-meme, un effet protecteur (auto-protec- 

 tion)." 



Drzewina and Bohn worked much with colloids of the heavy 

 metals, particularly with colloidal silver. Accordingly we have 

 used the same reagent, made as follows, from directions furnished 

 by Dr. Terry-McCoy of the Department of Chemistry of the Uni- 

 versity of Chicago: "Dissolve 4 gm. of commercial dextrine in 



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