MORPHOLOGY AND BIOLOGY. 27 



chemical agencies it may be stated that a large number 

 of such substances are capable of destroying them. A 

 1 to 300 solution of quinine sulphate will kill the 

 amoebae of man within a few minutes, while weak 

 solutions of hydrogen dioxide, permanganate of 

 potassium, sulphate of copper, nitrate of silver, argy- 

 rol, and dilute acids are efficient agents in the de- 

 struction of this class of organisms. Unfortunately, 

 the parasitic amoebae are not as easily destroyed when 

 present in the intestine as they are upon a microscopic 

 slide, as the pathogenic forms penetrate deep into 

 the tissues where chemical solutions cannot reach 

 them. Our knowledge is incomplete as regards the 

 effect of chemicals upon the amoebae of man, as most 

 of the experimental work has been done with cultures 

 of free-living species. In a recent paper Vedder gives 

 in detail some very important experiments in which 

 he found that ipecac, not de-emetized, killed a cul- 

 tural amoeba in dilutions as high as 1-50,000 in 24 

 hours; emetin, 1-100,000; quinine, 1-200,000; and 

 silver nitrate 1-300,000. How far his results apply 

 to the parasitic amoebae of man is undetermined. 



Many other chemicals, strong electrical currents, 

 and the Roentgen rays are capable of destroying 

 amoebae, but none of these agents have proven of 

 much service in the treatment of amoebic dysentery. 



