et eee 
—.- oa ee 
912 
distributed in the nuclear cavity as an achromatic network. Multiplication 
takes place by fission and spore formation. In reproduction by spore formation, 
the chromatic substance of the nucleus divides into eight parts and, after solution 
of the nuclear membrane, these become arranged in the protoplasm of the ameebie 
as daughter nuclei, and from these nuclei young ameebe eventually always result. 
This reproduction is brought about in a complex manner, somewhat as follows: 
During the encystment of the ameebe, fructification occurs. The nucleus divides 
mitotically, and from the resulting two nuclei two pairs of daughter nuclei are 
formed in such a manner that each pair has an element from each original 
nucleus which has been produced by mitotic division. After wandering in the 
protoplasm for a certain time, these two pairs of daughter nuclei coalesce, so 
that we again have produced a cell with two nuclei. After a time these nuclei 
again part by primitive mitosis, giving rise to four nuclei and this process is 
finally once more repeated, giving an ameeba with eight nuclear cysts. About 
each of these new cysts protoplasm collects, and from them eight young amebex 
develop in the next host. 
E. histolytica differs sharply from #. coli in having a distinctly formed ecto- 
plasm, which is very refractile and tenaceous. This latter property of the ecto-' 
plasm of this amebe enables it to penetrate between the epithelial cells lining 
the mucosa of the colon. 
The nucleus of HL. histolytica is poor in chromatin and it therefore is difficult 
to recognize; it changes its shape easily and is always excentrically located. 
This ameba multiples by fission and a kind of budding or sporogony, the 
nucleus dividing amitotically. Under unfavorable conditions spores are formed. 
The nucleus expels some chromatin into the endoplasm, degenerates, and may then 
be seen to be extruded from the parasite. As the little masses of chromatin 
approach the periphery, the ectoplasm becomes bulged out and finally the particles 
of chromatin, with little masses of protoplasm measuring from 3 to 7 m in 
diameter, are cut off and become separated from the remainder of the ameeba, 
which now dies. These masses contain a concentric, thread-like structure, secrete 
an opaque membrane and the further processes of development finally become 
invisible. These bodies constitute the new infecting agent. 
The paper of Schaudinn attracted a great deal of attention and some 
more recent observers have confirmed his results; others have accepted 
them as established and a few, in addition to confirming his principal 
observations, have elaborated other characteristics which distinguish 
between the species. Among the latter, Charles F. Craig’s work * may 
be noticed. 
‘Craig’s conclusions, broadly speaking, confirm those of Schaudinn, 
but he proposes H. dysenteria as the name of the pathogenic species. 
His descriptions differ from those of Schaudinn somewhat in minor 
details and he adds a number of other distinguishing points which are 
intended to render the determination of species more practicable from 
a simple microscopical examination of the feces. 
Craig’s summary of the differences between these species is as follows: 
FRESH PREPARATION.—NSize—HE. dysenterie usually considerably larger than 
BE, coli. 
Color.—E. dysenteriew considerably lighter in color and much more refractive 
than BH, coli, 
*Am, Med. (1905), 9, 854, 897, 973. 
