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II. BIOLOGY OF AM@BA. 
In addition to the strictly biological problems, such as the determina- 
tion of species, life cycle, etc., there are others more nearly bordering 
upon pathology, the accurate determination of which is vital to an un- 
derstanding of the disease-producing properties of the parasites. This, 
for example, is shown in divisions of species into pathogenic and non- 
pathogenic ones. We do not like to take issue with the zoélogist upon 
the establishment of species, but when he carries his work as far as the 
determination of the pathogenicity of individual species, we feel justified 
in entering the discussion and in so doing it may be necessary, in meet- 
ing the issues involved, to use some criticism of a destructive character 
upon questions which are purely zodlogical, without offering a remedy. 
To this extent only will we invade the field of the zodlogist, with the 
exception of considering views which bear directly upon the medical 
aspect of the subject. 
Many discussions of life cycles, classifications, and methods of repro- 
duction of amcebe, of interest to medical men, have been published from 
time to time, but these have largely fallen into disuse from lack of con- 
firmation and therefore need not be entered into here. 
REVIEW OF RECENT LITERATURE. 
In 1903, the late Prof. F. Schaudinn? contributed valuable information on this 
subject, which at once attracted much attention. Many of his observations have 
repeatedly been confirmed, while other of his statements have been elaborated by 
subsequent writers. Schaudinn established a new genus, Hntameba, to include 
those amebe found in the human intestine, and in this new genus he described 
two species H. coli and H. histolytica; the former the so-called harmless com- 
mensal and the latter a true dysentery producer. 
Briefly his observations were as follows: 
The genus Hntameba includes the amebe which inhabit the intestine of man. 
Two species are described, one pathogenic and the other non-pathogenic; they 
may both at times be found in the same diseased intestine, but obviously not 
together in a normal bowel. 
BE. coli (the type species) is considered to be harmless and perhaps to be the 
one reported by Lisch,* but first accurately described by Casagrandi and Barba- 
gallo. EH. histolytica is the pathogenic species and is identical with Jurgen’s 
cat ameeba. 
The chief characteristics of these two species are as follows: 
HE. coli, when at rest, shows no sharp distinction between ectoplasm and endo- 
plasm, but this differentiation occurs to a moderate degree in the pseudopodia of 
the moving parasite. 
The nucleus is centrally placed, vesicular (during the vegetative stage), and 
has a distinct, compact, nuclear membrane. In the center of the nucleus is a 
nucleolus, which is formed of plastin and chromatin. Other chromatin is also 
*Arb. a. d. k. Gsndhtsamte, Berl. (1903), 19, 547-576. 
*Schaudinn states that Lisch’s description is so incomplete that he is unable to 
say whether Lésch had first encountered FH. coli or FE. histolytica; however, he is 
inclined to believe from Lésch’s description that H. coli was the species described. 
