546 CLASSIFICATION AND MORPHOLOGY OF AMEBA 



in 50 per cent, of American soldiers in Manila and 72 per cent, of 

 Philippine scouts. In order to find Amoeba coli in the stools of 

 healthy persons it is practically always necessary to administer a 

 large dose of salts, such as sulphate of magnesium or sodium. The 

 discussion as to pathogenic and non-pathogenic amebse has been of 

 the greatest importance, since it makes a good deal of difference 

 whether all amebse may occasionally become pathogenic, or whether 

 among them, as among bacteria, certain definite types produce specific 

 diseases, while others are perfectly harmless and non-pathogenic. 

 In animals the same conditions, of course, prevail, and in them, 

 apparently, as in man, most amebse inhabit the intestines as harmless 

 commensales, but likewise one species has already been found which 

 evidently is a very dangerous pathogenic parasite. 



Entamceba coli, as described by Schaudinn, Craig, and others, con- 

 sists of a mass of protoplasm, containing a well-defined nucleus and 

 generally one or more nucleoli. Sometimes a non-contractile vacuole is 

 present, but rarely, if ever, more than one vacuole. The differ- 

 entiation between the entoplasm and ectoplasm is very faint; the 

 organism is very sluggishly motile. Reproduction under favorable 

 conditions occurs by simple division, under unfavorable conditions 

 after encystation followed by the formation of eight daughter cells 

 in the cyst. The daughter cells after solution or rupture of the cyst 

 membrane are set free and develop into young amebse. Entamoeba 

 coli varies in size between 8 to 50 micra, generally between 25 to 30 

 micra. When not in motion it is spherical in shape. Its pseudopodia 

 are rounded or lobose, never sharply pointed. It is of a dull grayish 

 color, and takes up red blood corpuscles very rarely even if they are 

 present in the feces. Bacteria are often found in the finely granular 

 protoplasm. The nucleus, 5 to 8 micra in diameter, is generally 

 situated a little to one side of the centre. It has a thick, easily seen 

 nuclear membrane and possesses a large amount of chromatin. In 

 stained specimens the ectoplasm dyes very dimly, the entoplasm 

 intensely. The latter is composed of well-defined granules, among 

 which engulfed bacteria can generally be seen; the chromatin of the 

 nucleus is shown as short strands or round granules. The encysted 

 forms do not take the stain on account of their firm capsule. When 

 encystation occurs the organism* becomes perfectly motionless and 

 develops from its spherical periphery a highly refractive hyaline 

 membrane which finally acquires a double outline or contour and 

 appears irregularly striated. During the formation of the cyst wall 

 the organism apparently contracts and loses about one-third of the 

 diameter it had when encystation began. The protoplasm in the 

 cyst becomes hyalin, the nucleus breaks up, and eight daughter nuclei 

 are formed, around these cytoplasm is distributed, and in this manner 

 eight young cells originate in the interior of the cyst. 



Entamoeba Hystolytica. This is the pathogenic type of ameba 

 parasitic in the intestines of man, and is the cause of chronic amebic 



