146 AMEB.E 



under suitable conditions. Perhaps some slight injury to the 

 membranes or the combined action of the amebse and certain 

 bacteria is necessary to start the process. Parallel cases of 

 parasites which may live for a long time as harmless messmates 

 and then, under favorable conditions, become pathogenic are 

 well known; one of the best examples is the intestinal ciliate, 

 Balantidium coli. This would account for the presence of 

 Endamoeba gingivalis in healthy mouths. It is significant that in 

 her investigation of school children in New York, Anna Williams 

 found only 30 per cent of apparently healthy mouths, and 94 

 per cent of mouths with spongy and bleeding gums, infected. 

 As to the statement that amebse still exist in pus pockets after 

 treatment with emetin, even when there is marked improvement 

 in clinical symptoms, there is no doubt but that the number of 

 amebse is greatly reduced, and those on the frontier where the 

 most damage is done are undoubtedly killed, since they are most 

 exposed to emetin in the blood. The ineffectiveness of emetin 

 against amebae which are not directly in the tissues has been 

 demonstrated in the case of the intestinal amebse which are not 

 tissue parasites (see p. 139). Again, were the improvement 

 following treatment with emetine due to favorable action on the 

 tissue cells, such improvement would invariably follow. That 

 emetin affects other organisms besides amebse is true, but it is 

 more active against these protozoans than against any other or- 

 ganisms, as far as is known. The complete cure of pyorrhea 

 which emetin sometimes effects, the usual improvement shown 

 after its use, and the occasional failure of it, all point to the in- 

 strumentality of amebse in causing or aggravating the disease, 

 but indicate that they may be aided and abetted, or entirely re- 

 placed, by bacteria or other organisms. 



There is some evidence that chronic tonsilitis also is often 

 caused by E. gingivalis, since this parasite is found in the ma- 

 jority of diseased tonsils, irritating the tissues and opening the 

 road for bacteria. 



An indirect relation of this same mouth ameba to certain types 

 of goitre also has been shown to be very probable. Evans, 

 Middleton and Smith found that diseased tonsils and nasal 

 passages and enlarged thyroid glands (goitre) are frequent com- 

 panions in the goitre belt of Wisconsin. They believe that the 

 amebse injure the tissues sufficiently to give ample opportunity 



