PARASITIC PROTOZOA JN RKLATIO?,' TO TlfE WAR. 299 



and has only one nucleus, thai stnicture is relatively large, heing 

 as much as 5/a in dianiater. 



In cases of relapse, or those that have remained witiioiit 

 treatment for a long time, a generation of smaller trophozoites 

 is associated with or replaces the larger ones, and these small 

 parasites tend to lie on or near the surface of the intestinal 

 mucosa. The smaller forms are the senile or pre-cyst generation 

 of Darling. The small entam»:eb?e were described separately by 

 Elmassian in 1909 as EntanKvba miunfa. the parasites being 

 obtained from a case of chronic dysentery in Paraguay. It is 

 interesting to remark that in subacute cases of amoebic dysentery, 

 with much mucus in the stools, but not much blood, the parasites 

 seen are of the type formerly described separately as Entanio'ba 

 tetragena. 



A patient showing acute symptoms of dysentery is not neces- 

 sarily infective to others, for he is often merely harbouring the 

 large trophozoites of E. histolytica, which, by animal experiments, 

 have been shown usually to be non-infective when fed by the 

 mottth. The stools of convalescent and recovered patients may 

 still contain cysts, and so such persons may act as carriers of the 

 disease. Natives in tropical countries may act as carriers. Erit(p- 

 mocba histolytica is transmitted from man to man in the encysted 

 condition. Food and water contaminated with infected excrement 

 are common sources of infection, and dust contaminated with 

 f?ecal material may be infective. It has also been proved that 

 various flies can transfer the cysts of E. histolytica from place 

 to place. Flies feed on infected human excrement, and then visit 

 fruit, vegetables, nu"lk. etc., intended for human consumption. 

 The cysts of the eniamueba pass unharmed through the alimentary 

 canals of the insects and pass out with their excrement on to 

 the surface of human food, which is a source of infection to 

 persons partaking thereof. 



It may be mentioned that rats can serve as reservoirs of 

 amoebic dysentery, as well as the human carriers already men- 

 tioned. 



Ulcers due to Entauuvha histolytica occur in the large intes- 

 tine. The entamoebce may invade the liver, producing abscesses 

 in that organ. The subcutaneous injection of 10 to 12 grains of 

 emetine, in daily doses of i grain, will usually be foimd effica- 

 cious in anueobic dysentery, though the minuta form of the 

 parasite may be relatively resistant thereto. Emetine bismuthous 

 iodide by the mouth, in doses of 3 grains per day for 12 days, has 

 also given good results, as well as emetine hydrochloride by the 

 mouth. 



The dysentery-producing entamoebre must be distinguished 

 from Entamoeba coli, a parasite which may be found in the ali- 

 mentary tracts of healthy persons. E. coli divides by binary 

 fission or sometimes by schizogony into eight daughter forms. 

 The cysts contain eight nuclei when mature (Fig. 3). They 

 measiu-e about 15/1 to 20/x in diameter, and may reach up to 

 30/i, and so are slightly larger than those of E.histolytica. The 



