Nov. i r i9*> Control of Fluke Diseases 201 



alkaline solutions. The tap water at Rice Institute, which is strongly 

 alkaline because of the presence of sodium carbonate, when used in a 

 1 to 1,000,000 solution of copper sulphate was apparently as effective 

 as distilled water, even after standing for 24 hours to allow time for 

 possible precipitation of the copper. 



Since organic matter in solution rapidly precipitates copper, water 

 containing considerable quantities of it should receive larger quantities of 

 copper sulphate to make up for loss by precipitation. The concentration 

 of copper sulphate necessary to destroy typhoid bacilli, according to 

 Rettger and Endicott (17), was four times as great in water containing 

 0.01 per cent peptone as in distilled water and 40 times as great in the 

 presence of 1 per cent peptone. Moore and Kellerman (12) advise an 

 increase of 2 per cent in the concentration used to kill algae for each 

 part per 100,000 of organic matter. It is probable that a similar 

 increase in the amount of copper used against snails would be sufficient 

 to counteract the effect of the organic matter. 



The presence of algae in the water has a marked effect on the action 

 of copper salts on snails, since the algae, which are killed by the salts, 

 absorb them. Bado (2) has demonstrated considerable quantities of 

 copper in the ash of algae which had been exposed to copper sulphate in 

 dilute solution, and he states that it is absorbed at different rates by 

 different species. In a preliminary experiment, the writer found that 

 snails placed in one liter of a 1 to 1 ,000,000 solution of copper sulphate, 

 together with a large handful of algae (Vaucheria and attached diatoms) 

 although they showed symptoms for a few hours after immersion, sub- 

 sequently revived and on the following day were as active as the controls. 

 To test more accurately the effect of algae, a quantity of fresh green 

 algae was rinsed and then squeezed like a sponge until water was no 

 longer expelled by moderate pressure. Quantities of this weighing 0.25, 

 0.5, 1, 2, 3, 4, and 5 gm. were placed in liters of a 1 to 1,000,000 copper- 

 sulphate solution, and snails (Physa occidentalis) were placed in each. 

 The snails in the jars containing up to 1 gm. of the wet algae (1 gm. = 150 

 mgm. dry weight) died as quickly as did the controls in a simple copper- 

 sulphate solution. Those in jars containing 2, 3, and 4 gm., although 

 prostrate within 24 hours, still responded weakly to stimuli at the end of 

 48 hours but did not revive when placed in fresh water. One-third of 

 the snails in the jar with 5 gm. of algae partially revived in the solution. 

 A second experiment, similarly conducted, but with the use of Spirogyra, 

 one of the algae most susceptible to copper salts, was tried. In this ex- 

 periment only 1, 2, and 3 gm. quantities were used. The snails with 1 

 gm. of Spirogyra did not die within 48 hours but failed to revive in fresh 

 water and died within 48 hours after being refreshed. Of those with 2 

 gm. 50 per cent revived after being refreshed, whereas of those with 3 gm. 

 all revived. 



