SEA-FISHERIES LABORATORY. 343 



leads in a few hours to the death of the tadpoles. This 

 observation has been confirmed by Binger,t and more 

 recently by Roaf and Whitley, J who have also shown that 

 a trace of colloidal silver in suspension leads rapidly to a 

 fatal result, while colloidal platinum under like conditions 

 is quite harmless. 



It has been suggested to me by Professor B. Moore 

 that possibly the cause of the poisonous action in some 

 organisms and immunity in others, may be due to those 

 organisms which are poisoned throwing out excretory 

 substances which dissolve copper and form soluble 

 poisonous compounds which are absorbed, and so lead to 

 the toxic effects. 



The matter has also been discussed recently as one 

 which may be of importance in killing algae and 

 pathogenic organisms in water supplies. Dr. Gr. Moore, 

 of Washington, found that one part in fifty millions was 

 sufficient to kill off fresh-water alga? in water-cress beds* 

 and that 1 in 100,000 would kill cholera and typhoid 

 organisms in 4 to 5 hours. Iiideal and Baines (1904) 

 found that 24 hours in a copper vessel was sufficient to 

 free the water from typhoid and colon bacilli. Bassett- 

 Smith,* as the result of a number of experiments, states 

 that " Bacillus typhosus is more easily killed than others 

 of the coli group, being destroyed in 12 hours with the 

 1 in 10,000 dilution " [sulphate of copper]. He also finds 

 that " Zinc, or iron coated with zinc, though less rapid in 

 its action than copper, yet after 24 to 48 hours appears to 

 free the water from typhoid organisms, and is the most 



f Ibid., 1897, vol. 22, p. xiv. (Physiol. Soc. Proo.) 



J Communicated by the authors (Biochemical Department, University 

 of Liverpool) — the paper not being yet published. 



* Journ. of Preventive Medicine, Julv, 1905. 



