xiii. b, 5 Haughwout: Flagellated and Ciliated Protozoa 249 



and membranelles of the adoral zone of the organism when 

 closely and persistently applied to the surface of the tissue? 

 Once the entrance is forced, it would be about as easy for one 

 of these ciliates to worm its way in as it would be for an 

 amoeba. Their bodies are plastic to a degree that at times 

 superficially resembles pseudopodia formation, and they accom- 

 modate themselves to every obstacle they meet as may be 

 readily seen by any one who will take the time to study a cover 

 slip preparation from a case of Balantidium infection containing 

 actively moving parasites. 



After having gained entrance to the tissues, it seems to me 

 for the present, reasonable to believe that the nutrition of these 

 organisms continues to be holozoic within the tissues, so we are 

 left to speculate as to whether necrosis in the tissues, where 

 involvement is unaccompanied by the presence of bacteria, is 

 due to the secretion by the organism of some special cytolytic 

 ferment, or whether it is brought about "by the action on the 

 tissues of the normal katabolic products of the parasites, a 

 theory which seems to me not wholly devoid of reason. This 

 may also apply as well to Entamoeba histolytica as to the flagel- 

 lates and ciliates. 



But aside from tissue penetration, the situation contains fur- 

 ther inconsistencies. Balantidium, from such reports and per- 

 sonal experiences as are available to me at this time, seems to 

 be more frequently seen in the blood vessels of the intestine 

 than Entamoeba. In spite of this, however, Balantidium is never 

 found in the liver; whereas Entamoeba is very frequently found 

 there and in other parts of the body. Why is this? 



May we not find our answer in the general tendency of the 

 flagellated and ciliated protozoa, spermatozoa, and the like to 

 swim against the current, whereas the relatively passive enta- 

 moeba? are carried willy-nilly by any current to a point where 

 they meet with some obstruction, finally to lodge and reproduce, 

 provided the conditions are favorable? Balantidium and Tri- 

 chomonas, with their powerful, well-developed motile organs, 

 would surely have less trouble in stemming the tide of the 

 slow-moving venous and lymph circulation than even the poorly 

 equipped spermatozoon has in breasting the current of the 

 ciliated Fallopian tubes. And yet the population of the world 

 attests the success of the spermatozoon, and the absence or com- 

 parative absence of extra-intestinal infections with Balantidium, 

 Trichomonas, Lamblia, and the like seems to betoken equal 



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