ENTAMCEBA HISTOLYTICA 191 



when the acute symptoms have abated, the carrier condition maintains, 

 when precystic amoebae and cysts are passed. Certain individuals become 

 infected without suffering from acute dysentery, the infection being 

 detected only as a result of microscopic examination of the faeces. Those 

 who become carriers after acute attacks have been termed convalescent 

 carriers by Walker and Sellards (1913), and the others contact carriers. 

 Such carriers may remain infected for many years, probably for the rest 

 of their lives, without at any time being seriously troubled by their 

 infection. In this respect the infections with E. histolytica are very 

 similar to those produced by pathogenic bacteria. 



As would be expected from the above account, the signs of an infection 

 with E. histolytica vary considerably. In the acute condition, if there 

 is extensive ulceration, the quantity of mucus and blood and the number 

 of amoebse passed in the stool may be considerable. The mucus is 

 generally of a brownish colour and the blood of a dark red tint. If 

 ordinary food has been continued, as is often the case, and the large 

 intestine has not been emptied of faecal matter, this will be present, and 

 mixed with the blood and mucus to a varying extent. It is not surprising 

 that the amoebae are found in largest numbers in the mucus which has 

 been discharged from the ulcers or from the irritated surface in their 

 immediate neighbourhood. In some cases where active multiplication 

 of amoebae is in progress over a large surface of the bowel, and food is 

 continually taken, the stool may be of a soft brown consistency, which 

 on first inspection appears to differ little from the normal. It will be 

 found, however, that there is an intimate mixture of faecal matter and 

 mucus in which large numbers of amoebae occur. Sometimes the stool 

 is more liquid and of diarrhoeic nature (amoebic diarrhoea), when careful 

 inspection will reveal small flakes of mucus in which numerous amoebae 

 may be found. Such cases may be due to superficial invasion of extensive 

 areas. In many cases it is impossible to decide whether the symptoms 

 noted are due entirely to the amoebae, or whether they are partly the 

 result of secondary bacterial infection of the already damaged tissues. 

 It would be expected that an ulcerated intestine, though producing no 

 symptoms, would be more liable than a healthy one to be irritated by 

 food or bacteria, and if diarrhoea results from such irritation it is difficult 

 to affirm that it is due to the amoebae, though many may appear in the 

 stool. It not infrequently happens that individuals who are undoubtedly 

 infected with E. histolytica rarely pass amoebae in the stools, so that many 

 examinations have to be undertaken before an absolutely certain diagnosis 

 can be made. In these cases inspection of the mucosa of the lower bowel 

 by means of the sigmoidoscope has yielded valuable information. Not 

 only can the ulcerated areas be seen, but scrapings from them will imme- 



