320 The Philippine Journal of Science ms 



in water and other external sources are capable of living para- 

 sitically in the intestine of man and of producing dysentery, at 

 least the pathogenic species is capable of living and multiplying 

 indefinitely outside of the body of its host. Such a characteristic 

 of Entamoeba histolytica would be unique among pathogenic 

 microorganisms, and would, indeed, constitute entamoebic dys- 

 entery the most formidable disease of mankind and the least 

 amenable to prophylaxis. Not only the water, but everything 

 in the Tropics, even the air, contains amoebae, motile or encysted 

 in greater or lesser numbers, and efficient preventive measures 

 against this disease would be practically impossible. 



On the other hand, the experimental determination that enta- 

 moebic dysentery is caused by one species of amoeboid organism 

 only, and that this species is a strict or obligatory parasite which 

 cannot multiply outside of the body of its host, profoundly limits 

 the prophylactic problem of this disease; indeed, reduces it to 

 almost, but not quite, the same level as that of other intestinal 

 infectious diseases, such as bacillary dj-sentery, typhoid fever, 

 and cholera. Every case of entamoebic dysentery, under these 

 conditions, must arise directly or indirectly from some preceding 

 case of entamoebic dysentery, and the prophylactic problem be- 

 comes that of protecting the well from cases of the disease, the 

 sanitary disposal of the dejecta of the diseased, and the detection 

 and treatment of "carriers" of the pathogenic entamoeba. 



Every acute case of entamoebic dysentery is constantly passing 

 in his stools greater or smaller numbers of Entamoeba histolytica; 

 but in dysenteric stools the entamoebse are all in the motile stage, 

 in which they are probably less resistant to external influence 

 than any other intestinal organisms. They not only will not 

 live, but even disintegrate within a few hours after being passed 

 in the faeces. It is also probable that in this stage they are 

 incapable of surviving passage through the normal stomach, but 

 are destroyed by the acidity of its contents. Of the 4 men who 

 ingested the motile Entamoeba histolytica in my experiments, 3, 

 or 75 per cent, became infected ; but these infections were secured 

 under the most favorable circumstances, large numbers of the 

 organism being ingested, together with magnesium oxide to 

 neutralize the acidity of the stomach. It is unfortunate that 

 some of these men were not fed the entamoebae without neutraliz- 

 ing the acidity of the stomach contents, in order to determine 

 experimentally the possibility of infecting with the motile stage 

 under natural conditions. Darling (1913) states that infections 

 invariably fail when only the motile (trophozoite) stage of Enta- 

 moeba histolytica is fed to kittens. Shirota (1912) makes a 



