Nov. i, 1920 



Control 0} Fluke Diseases 



197 



being the cheapest copper salt, was therefore selected for further experi- 

 mentation. 



Chemical. 



Dilution. 



24 

 hours. 



As 2 3 



Ba(N0 3 ) 2 



CaOCl 2 



CaOCl 2 



Ca(OH) 2 



CuCl 2 



CuS0 4 



CuS0 4 



HgCl a 



NaCl 



NaCN 



NaCN 



(NH 4 ) 2 S0 4 



(NH 4 ) 2 S0 4 



Pb(CH 2 COOH) 2 



Pb(CH 2 COOH)„ 



ZnCl 2 



ZnS6 4 



1 to 1,000,000 



1 to 100,000 



1.3 available chlorin per 



1,000,000. 

 2.6 available chlorin per 



1,000,000. 



1 to 10,000 



1 to 100,000 



1 to 100,000 



1 to 1,000,000 



1 to 1,000,000 



1 to 1,000 



1 to 100,000 



1 to 1,000,000 



1 to 100,000 



1 to 1,000,000 



1 to 100,000 



1 to 1,000,000 



1 to 1,000,000 



1 to 1,000,000 



7© 

 3 + 



\2 + + 



± 



o Figures beside symbols indicate number of snails out of the 10 used in the experiment. 



The effect of copper salts on various kinds of organisms is extremely 

 variable. Their highly toxic effect on algae, first demonstrated by 

 Moore and Kellerman (ji), is well known, and copper sulphate is exten- 

 sively and successfully used in eliminating algae from ponds and reser- 

 voirs. Copper sulphate is effective against some algae in dilutions up 

 to i part in 25,000,000 or more parts of water but is commonly used in 

 the proportion of 1 part to from 1,000,000 to 3,000,000 parts of water. 

 Its bactericidal action is less marked and varies greatly with temperature. 

 At 20 C, in water relatively free from organic matter, all pathogenic 

 bacteria are destroyed in 24 hours at a dilution of 1 part to 400,000 

 parts of water. Peters (14) showed that the concentration necessaiy 

 to kill instantly certain protozoa was 12 to 60 X io -8 gram molecular 

 parts per cubic centimeter of water (about 3 to 15 parts per million). 

 The toxic effect of copper on fungi is as striking as its effect on algae 

 and is taken advantage of commercially in the use of Bordeaux mixture 

 for spraying trees and vines. 



Curiously enough the effect of copper salts on both higher plants and 

 higher animals is in general far less toxic than it is on lower animals 

 and plants. In dilute solutions copper sulphate has a stimulating action 

 on the growth of many higher plants, having been tested particularly 

 on various grains. In the animal series, copper salts are usually 



