144 AMEB.E 



under suitable conditions. Perhaps some slight injury to the 

 membranes or the combined action of the amebae 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 g'ngivalis 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 

 amebae 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 free-swimming stages of Craigia 

 (see p. 139). Again, were the improvement following treatment 

 with emetin due to favorable action on the tissue cells, such im- 

 provement would invariably follow. That emetin affects other 

 organisms besides amebse is true, but it is more active against 

 these protozoans than against any other organisms, as far as is 

 known. The complete cure of pyorrhea which emetin sometimes 

 effects, the almost invariable improvement shown after its use, 

 and the occasional failure of it, all point to the instrumentality 

 of amebae in causing or aggravating the disease, but indicate 

 that they may be aided and abetted, or entirely replaced, 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 

 amebae injure the tissues sufficiently to give ample opportunity 



