N 



PART II. CHARACTERS AND DIAGNOSIS 47 



It sometimes, though rarely, happens that amoebae cannot 

 be found in the stool, even after several examinations, when actual 

 amoebic ulceration of the large intestine is present. Amoebic 

 abscess of the liver is not infrequent when no amoebae can be 

 found in the stool. We have discussed the possibility of bacillary 

 dysentery attacking a person who is infected with E. coli or is a 

 carrier of E. histolytica ; but there is another class of case which 

 needs consideration, though we have not come across an example. 

 These are cases in which the E. histolytica is actively concerned 

 in the dysenteric process while a true bacillary dysentery exists 

 also. These would be quite different from cases of bacillary 

 dysentery occurring in carriers in which the E. histolytica are 

 not actively concerned. If the case is a carrier of E. histolytica 

 and develops bacillary dysentery, the disease which demands 

 urgent treatment is the bacillary infection, but if the case is one 

 of true amoebic dysentery combined with true bacillary dysentery 

 it is probable that both diseases should be treated at once. The 

 diagnosis of such cases can only be made by recognizing the 

 clinical and microscopical appearances of bacillary dysentery, 

 isolating one or more of the dysentery bacilli, and at the same 

 time recognizing in the stool the actively motile amoebae with 

 their included red blood corpuscles. Such doubly acute cases are 

 naturally of rare occurrence, but they must not be confused with 

 cases of bacillary dysentery in which free forms of E. coli or 

 " minuta " forms of E. histolytica are present in the stool. 



(2) Characters and Diagnosis of Cysts of E$ ! histolytica. 



The characters of the cysts of E. histolytica with the one, two, 

 or four nuclei, the vacuoles and chromidial bodies are now too well 

 known to need further description from us. We would point out, 

 however, how closely the cysts may at times be simulated by the 

 I-cysts, especially, as sometimes happens, these are devoid of 

 I-bodies. In such cases the nucleus may be larger than usual, 

 and it may be exceedingly difficult to decide whether one is dealing 

 with E. histolytica cysts or not. This difficulty may be still greater 

 in films containing I-cysts stained by the iron haematoxylin 

 method. There the iodophilic body appears not as the refractile 

 structure seen in the unfixed material, but as a vacuolic area by the 

 side of which is the nucleus giving the appearance of a vacuolated 

 E. histolytica cyst with a single nucleus (Plate III, figs. 12-17).* In 

 these cases the nucleus is generally smaller than the nucleus of the 

 unenucleated E. histolytica cyst, and, moreover, is structurally 



* See inset betiveen pages 148 and 149. 



