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921 
will take on a pink tint after the introduction of very dilute solutions 
of neutral red. 
The granular material of the endoplasm may be entirely absent or 
abundant, and the variation in size of the granules is also decided. 
These bodies, if present, are not visible in the encysted amcebe. Their 
composition and significance is not understood, but in some instances, 
at least, they appear to be chromatic. They probably have some function 
in the metabolism of the parasite and they may eventually be of value 
in species determination. Vacuoles are never seen in the young amoeba 
nor in the encysted one. One or more, however, of different sizes may be 
present in the adult parasites, and they are usually most numerous just 
before encystment. 
Quite frequently these vacuoles contain numerous, small, actively 
motile granules. The significance of the vacuoles is not fully under- 
stood. However, Mouton, working with cultures of amcebx, showed that 
one of the vacuoles was contractile and that this one contained a digestive 
ferment. Vacuoles are more constantly present and more numerous in 
cultures of some amcebe than they are in others. 
The inclusion of red blood corpuscles, bacteria, and other foreign-formed 
elements under certain circumstances by some amcebe is a rather frequent 
phenomenon, and one difficult to understand. However, as has been 
stated in some of our previous communications, it is probably largely 
a mechanical process. In cultures, amcebe are often not tolerant of 
solutions containing blood, but by starting with very small amounts and 
gradually increasing the percentage of blood in the medium a condition 
may be obtained in which the parasites will engulf red blood corpuscles 
apparently exactly as they do in the intestine. This observation is 
facilitated if blood poor in hemoglobin be used. The process, whatever 
its significance, positively is not confined to one particular morphological 
type of ameeba; it can not be used as a differentiating characteristic 
between pathogenic and non-pathogenic species, and finally the oft- 
repeated statements that red blood corpuscles are digested by the amcebe 
is without foundation in fact. The damage which such cells manifest 
when extruded from amoebe, as they always are before encystment, has 
not been produced by any digestive process but, aside from some probable 
changes due to the mechanical action of the parasite, are damages which 
were present when the cell was ingested. We have watched amcebe 
containing red blood corpuscles for hours without seeing any evidence 
of a specific action of the amoebe upon the corpuscles. 
It is simply absurd to employ a small difference in the number of red 
blood corpuscles which two different amcebe may happen to have within 
them, as a factor in species diagnosis. This is emphasized when we 
remember that it is not very uncommon to find one, two, or even as many 
as four red blood corpuscles in one of the common monads in a dysenteric 
