48 



infected persons whom they studied were, as a class, more prone 

 to suffer from dysentery or other intestinal diseases than un- 

 infected persons from the same walks in life. The later workers 

 —whose results are here recorded — have obtained concordant 

 results. Histories of all the cases studied were obtained, as far 

 as possible, and recorded : and inspection of these records shows 

 that a past or present history of dysentery is apparently no 

 commoner in persons infected with E. histolytica tKan in those who 

 are nominally ' uninfected '. The figures are, however, for various 

 reasons inconclusive. For example, when a person is found to 

 have suffered in the past from ' dysentery ', it is now usually im- 

 possible to ascertain its cause. The complaint was generally 

 diagnosed on clinical grounds ; and even if the patient is found 

 later to harbour E. histolytica it is by no means certain that this 

 parasite was the cause of the trouble. The patient may have 

 suffered from bacillary dysentery, whilst remaining a ' healthy ' 

 carrier of the amoeba ; or he may have acquired his infection 

 after the attack of dysentery. A history of ' diarrhoea ' is even 

 more difficult to interpret ; for there are but few who, on being 

 closely interrogated, are found not to have suffered, upon occasion, 

 from this common complaint. Furthermore, when a person has 

 been examined but once, and found ' negative ' for E. histolytica, 

 the conclusion that he is ' not infected ' is by no means warranted. 

 Consequently, in all our series the ' negative ' cases with a past 

 history of dysentery or diarrhoea cannot furnish us with reliable 

 statistics of the incidence of these diseases in persons uninfected 

 with E. histolytica. 



The findings, given for what they are worth, appear to be as 

 follows for the infected persons so far studied. The Liverpool 

 workers, in their first published' series, state of the ten cases of 

 E. histolytica infection investigated that 'none of them gave 

 a history of dysentery '. The full histories of the cases in their 

 later series are not recorded, but it seems unlikely that these 

 cases were — in this 'respect — substantially different from those in 

 the earlier series. Of the twenty-seven British carriers of E. his- 

 tolytica studied at Birmingham, Brighton, Bristol, Leeds, Sheffield, 

 and Reading, only one has a history of ' dysentery ', while three 

 are stated to have suffered from more or less serious attacks of 

 ' diarrhoea ' in the past. It is easy to pick out random samples 

 of twenty- seven individuals from the 'uninfected' persons in the 

 same series showing past records of diarrhoea or dysentery in 

 approximately the same proportion. It is noteworthy, moreover, 

 that there is not a single infected individual, in any series, with 

 a history of hepatic abscess.^ 



(2) Entamoeba coli. — It is now clear that E. coli, the large 

 harmless amoeba of the human bowel, occurs commonly through- 



' I exclude the case recorcled by Ai-mitage (1919) from the ' British ' series ; for 

 the patient,' though he apparently contracted an amoebic abscess of the liver, 

 followed by another in the brain, in England, and had never been in tropical or 

 subtropical countries, was a native of New Zealand. 



