28 LIMNOLOGY, WATER SUPPLY AND WASTE DISPOSAL 



(Fair, Chang and Morris 1945), we showed that anionic detergents 

 were noncysticidal at a concentration as high as 20,000 parts per mil- 

 lion. Neutral detergents, such as Hexyl-resorcinol, were cysticidal at a 

 concentration of 75 ppm in 10 minutes to 30-50 ppm in 120 minutes. 

 Cationic detergents were cysticidal at lower concentrations but some were 

 considerably more cysticidal than others. For instance, Fixanol, Sapamine, 

 Ceepryn, Zephiran, Ortho-7 and Nopco-QCL were cysticidal at 5-10 to 

 30 ppm in 10 to 120 minutes, while others, such as Emulsol-660B, were 

 not cysticidal even at 75 ppm in 10 minutes to 50 ppm in 120 minutes. 

 The cysticidal efficiency of cationic detergents was found to be affected 

 by the presence of proteins, lipoids, and probably also by greasy and soapy 

 substances. Anionic detergents were found to be good neutralizing agents 

 for cationic detergents (Fair, Chang and Morris 1945; Kessel and Moore 

 1946). 



IV. Discussion 



Is amoebiasis an important infection in this country? Besides the 

 nationwide distribution of cases of quiescent infection, about 3 to 4 thou- 

 sand cases of amoebic dysentery have been reported annually in the Public 

 Health Reports of the U. S. Public Health Service in the last 10 years. Of 

 these reported cases, about one third have been from the State of Missis- 

 sippi. Hence, it would seem that if amoebiasis is not a serious infection 

 in the country as a whole, it is so in Mississippi. 



While it would be absurd to think that polluted water is important 

 in spreading amoebic infection in areas where water supply is sanitarily 

 controlled, it would be equally absurd to think that polluted water is of 

 no importance in establishing the infection in areas where water supply 

 is still inadequately controlled. Judgment as to the more important mode 

 of transmission of this infection must be based on the local conditions 

 existing rather than on biased opinion. 



Since the present paper deals only with the problems in water-borne 

 amoebiasis, emphasis has been laid on this route of transmission. The 

 author, of course, has no intention of minimizing the other routes of trans- 

 mission when circumstances that favor the spreading of the infection by 

 such routes exist. From the epidemiological problems presented in the paper, 

 it is apparent that any argument for or against the water-borne theory is 

 circumstantial in nature, and so are the arguments for or against the theory 

 of other routes of spreading the infection. If diseases like typhoid and 

 bacillary dysentery result from unhygienic habits of eating and drinking, 

 so does amoebiasis. A very careful study of the epidemiology of the amoebic 

 dysentery as well as quiescent amoebiasis and of the effectiveness of vari- 

 ous methods of control in Mississippi may bring out valuable information 

 and throw more light on the subject of the mode of transmission of amoebia- 

 sis. 



The biological characteristics of the cysts of E. histolytica brought 

 together in the present paper provide us sufficient information as to the 



