420 



VETERINARY BACTERIOLOGY 



Councilman and Lafleur studied the pathology of the disease in 

 great detail. Schaudinri gave to the organism its present name of 

 E. histolytica, and described its morphology with accuracy. 



The disease has been reported from all sections of the world. 

 It seems to be much more prevalent in tropical than in temperate 

 climates, but -has been identified repeatedly in the United 

 States. 



Morphology. According to Craig, the morphology of this 

 organism varies so greatly in culture-media that only the forms 

 found in the feces can be regarded as typical. The organism under 



V,,a. 



4. 



6. 



Fig. 187. Entamceba histolytica: 1, Organism in motion a, Vacuoles; b, 

 red blood-cells; c, pseudopodium composed chiefly of ectoplasm. 2. Organ- 

 ism showing nucleus a, and vacuoles, 6. 3. Preliminary changes upon begin- 

 ning sporulation a, Vacuoles; b, chromatin masses escaping from the nucleus 

 and scattering through the cell. 4, Chromatin masses scattered through the 

 cell, b; c, vacuole. 5, Cell budding off spores, the chromatin masses or new 

 nuclei passing through the ectoplasm and escaping as spores. 6, Free spores 

 (adapted from Craig). 



these conditions varies in diameter to 50 (i or more, showing it 

 to be larger than E. coli. At rest, the organism is spherical or 

 ovoid; when in motion, its shape is extremely variable. It is 

 usually actively motile, throwing out pseudopodia much more 

 rapidly than E. coli. 



Color is absent, and the organism appears clear, or there may 

 be a greenish tinge, due to the presence of hemoglobin from the 

 blood in the feces and the blood-corpuscles engulfed. In the 

 larger cells, rarely in the smaller, the endoplasm and ectoplasm 

 may be quite sharply differentiated. The latter is hyaline, 



