14 CHEMICAL AGENTS AND PROTOPLASM [On. I 



the hydrogen in either the carboxyl-group or the amido- 

 group can be replaced by the metal. Likewise the hydrogen 

 of the amido-group in urea derivatives and many bases are 

 replaceable by metals. In the still more complicated protein 

 stuffs the H bound to the N or O can be replaced. Many 

 metals, indeed, like silver or mercury replace preferably the H 

 of the amido-groups, and on this account, perhaps, their salts 

 are especially poisonous. (LoE\v, '93, p. 34.) 



Salts of Hg, Ag, and Cu cause death to Spirogyra even in 

 a dilution of 1 : 1,000,000 ; the chlorophyll bodies being first 

 affected.* Upon the bacteria of splenic fever the double 

 cyanides of Ag, Hg, and Au are the most injurious, next those 

 of Cu, Pb, and Zn, and, finally, those of Pt, Ir, and Os. Tad- 

 poles and Tubifex are killed in 24 hours by solutions of CuSO 4 

 weaker than 0.00005%. (LocKE, '95, p. 327.) Among mer- 

 curic salts, splenic fever bacteria do not develop in 0.0003% 

 HgCl 2 in nutritive bouillon, nor 0.0125% in blood. Lactic acid 

 bacteria do not reproduce in 0.0007%. Mold spores are killed in 



* In this connection reference must be made to the posthumous paper of 

 NAGELI ('93), " Ueber oligodynamische Erscheinungen in lebenden Zellen." 

 This author found that water distilled in copper vessels or 1 litre of water in 

 which 12 clean copper coins had stood for four days acted fatally upon Spiro- 

 gyra. The water was found in one such case to contain 1 part Cu in 77,000,000 of 

 water. It was believed to be in solution in the form of the hydroxyd (CuH 2 O 2 ). 

 Similarly produced solutions of other metals, Ag, Zn, Fe, Pb, Hg, had a simi- 

 larly fatal effect upon Spirogyra. NAGELI believed that the effect of the metals 

 was not a chemical one, but was due to a new force " oligodynamic." Besides 

 the fact of the action of very dilute solutions, the only evidence he adduced for 

 the new force was based on the difference of action on the chlorophyl bands of 

 solutions of 1 : 1000 or 1 : 10,000 and 1 : 10,000,000. In the weaker solutions 

 ("oligodynamic" action) the bands alone were drawn away from the cell-wall, 

 in the stronger solution (chemical action) the whole peripheral protoplasm was 

 shrunken away. It does not seem necessary to invoke a new force to explain 

 the action of weak solutions: first, because the two actions are not sharply 

 separated, according to NAGELI'S own data ; secondly, because the chlorophyll 

 bands are in general more sensitive than the rest of the protoplasm (p. 5) ; 

 and, thirdly, because the action of so weak a solution is not surprising in view of 

 the fact that Spirogyra is one of the least resistant of organisms. Even in a 

 comparatively resistant organism, like Stentor, a solution of 1 : 80,000,000 HgCl 2 

 produces acclimatization to the poison and 1 : 10,000,000 has an injurious effect. 

 Yet between the action of such solutions and those of 1 : 1000 there is a complete 

 graduation in increasing effect. (Seep. 30.) Even in NAGEH'S experiments 

 solutions of less than 1 : 100,000,000 had little action. 



