63 



CHAPTEE VI. CONCLUDING EEMARKS. 



The observations recorded in foregoing chapters have de- 

 monstrated conclusively that all the commoner intestinal protozoa 

 of man occur now in the population of the British Isles. The 

 species actually recorded, up to the present moment, are the 

 following : 



(1. Entamoeba histolytica. 

 2. Entamoeba coli. 

 3. Jmdokmax nana. 

 4. lodamoeba biltschlii. 

 5. Dientamoeba fragilis. 



■iij-.„„^ . (6. Giardia intestinalis. 



Mastigophoea « /^j, -7 J • -7 ■ 



/-pii 11 + 1 I thiLomastix mesmli. 



^ ° ' [s. Trichomonas hominis. 



Infections with organisms belonging to the other main sub- 

 divisions of the Protozoa — the Sporozoa (e.g. Coccidia) and 

 Ciliophora (e.g. Balantidium) — have not yet been recorded. 



The probable frequency with which the above protozoa occur 

 in Britain has been discussed in Chapter IV, and need not be 

 considered again here. I would only remark that the estimates at 

 which I have arrived are based upon the results of an examination 

 of the stools of over 3,000 British residents, of all ages and both 

 sexes, who had never left these islands. They therefore have 

 a substantial basis. 



From a practical standpoint, the most important figures are 

 those relating to the incidence of infection wijbh Entamoeba histo- 

 lytica — the ' dysentery amoeba '. It has been demonstrated that 

 not less than 3-4 per cent, of the persons already examined 

 harbour this parasite ; and it is proba.ble that this figure — which 

 represents an absolute minimum — indicates that the true rate of 

 infection is of the order of 7 to 10 per cent. 



The evidence now obtained appears to show clearly that 

 E. histolytica — as well as many other intestinal protozoa — occurs 

 indigenously in Britain. It has been suggested, however, that 

 the occurrence of large numbers of carriers of this parasite among 

 our home population at the present day is a consequence of the 

 War. There is, indeed, good evidence to prove that our troops 

 returning from the tropics, and other places where E. histolytica 

 is known to be endemic, were often heavily infected ; and it is 

 true that an extensive infection of the resident civil population 

 of Britain has been demonstrated only since the outbreak of the 

 War. Consequently, the present state of affairs may be due to 

 the contamination of the civil population by an infected soldiery- 

 returning home. This conclusion is, I believe, unjustifiable and 

 almost certainly incorrect. All the evidence is against it. We 

 know— from the early records considered in Chapter II — that 

 long before the War E. histolytica occurred in British residents 



