D. Ward Cutler 
129 
reactions only as supporting the conclusions so derived. The investigations 
which I have made upon the action of various substances upon the amoebae 
were carried out with a piece of apparatus devised by Cropper and Drew 
(1914): 
“A plate of thin glass about three inches long and two inches wide has a narrow glass 
arm cemented to it along the short end, forming a projection upon which a small bottle 
can be hung by means of a piece of wire. The plate is covered over with a sheet of fine 
calico having a circular hole in the centre just large enough to permit of a cover glass resting 
on the plate with its edges almost touching the cloth all round. Two narrow strips of 
cigarette paper are placed on opposite sides of the aperture under the cover glass to prevent 
this from actually pressing on the slide... .Water or the solution to be employed is placed 
in the bottle, and is slowly conveyed by capillarity along a piece of lamp wick to the cloth, 
which is in this way kept continually moist. The amoebae are put into a drop of the 
solution on the cover slip, which is then inverted and allowed to rest on the slide in the way 
described.” 
I have used this apparatus constantly, both for observing the free vege¬ 
tative forms and also cysts, and have found it to be of great use. 
LITERATURE. 
The literature concerning E. histolytica is too vast to deal with here, 
moreover, most of the important papers have been summarised by others. 
It will suffice to outline the trend of previous research, reserving for the 
discussion at the end of the paper the points in which my results confirm or 
differ from those of other workers. 
Until recently there were supposed to be three species of parasitic amoebae 
in the human intestine capable of causing dysentery: E. histolytica Schaudinn, 
1903, E. tetragena Viereck, 1907, reinvestigated by Hartmann (1911), and 
E. minuta Elmassian, 1909. The accounts given of these organisms by the 
authors mentioned are well known and need not be dwelt upon. Darling, in 
Panama, demonstrated the identity of E. histolytica and E. tetragena. By 
inoculating cats he found that the large forms of the parasite, with the typical 
“histolytica ‘ n nucleus, predominated at the beginning of infection, but later 
were replaced by forms with the “ tetragena n type of nucleus, which passed 
into the cyst condition. More recently it has been shown that the “ tetragena ” 
forms give rise to smaller amoebae, the precystic stage of E. histolytica , these 
being identical with E. minuta Elmassian. Thus the three so-called species 
of amoebae producing dysentery represent in reality but different stages in 
the life history of one organism. 
Schaudinn also described a peculiar method of reproduction in E. histolytica, 
which he termed budding; he asserted, moreover, that small spores were 
1 While recognising that the original descriptions of the life cycle of E. histolytica were pro¬ 
bably based on observations on degenerate amoebae, I propose to adopt the term “histolytica” 
type of nucleus to denote one poor in chromatin, such as was once thought to be characteristic 
of E. histolytica. On the other hand the term “tetragena” type of nucleus signifies one rich in 
chromatin and containing a large karysome typical of E tetragena. 
9—2 
