HOST-PARASITE RELATIONS I INTESTINAL PROTOZOA 



skin, the eye, the bone marrow, and the lymph glands. 

 Whether the ''organisms" described in all of these cases 

 were amoebae of the species E. histolytica and whether 

 they were responsible for the various diseased conditions 

 ascribed to them are questions that will be discussed 

 later (see p. 109). 



6. CHANGES IN THE HOST DUE TO THE PRESENCE OF THE 

 PARASITE 



(i) The GENESIS of symptoms. Human hosts of 

 E. histolytica do not usually exhibit symptoms ; presum- 

 ably the parasites in most cases do not interfere suffi- 

 ciently with the normal functions of the body to bring 

 about obvious changes. Occasionally, however, symp- 

 toms appear, their character depending on the location 

 and severity of the lesions produced by the amcebae. Thus 

 primary or intestinal amcebiasis may give rise to amoebic 

 diarrhea or amoebic dysentery, and secondary amcebia- 

 sis to the various symptoms characteristic of amoebic 

 liver abscess, of amoebic abscesses in the lungs, brain 

 and spleen, and of lesions in other parts of the body. The 

 symptoms that result from the invasion of these organs 

 are rather well known and are described in various books 

 on protozoology and tropical medicine (see p. 198). 



The origin of the symptoms observed, however, is 

 practically unknown. For example, the most common 

 symptom of intestinal amcebiasis is diarrhea ; this is "ab- 

 normal frequency and liquidity of fecal discharges." 

 Two factors are involved here, (i) the exudation into 

 the intestinal lumen of serous fluid with a tendency to 

 putrefy and (2) an increase in peristaltic activity. Auer- 



96 



