'5
blood corpuscles altered by the presence of the parasite. Christophers 1 who studied and
described the various appearances assumed by these bodies states they are detached buds of
mononuclear cells or macrophages containing parasites. Treutlein.12 examining some of Rogers'
preparations has recently stated he has seen the. parasites in red cells, but no other observer as
far as I am aware has recently described the parasites as occurring in the red corpuscles. All
investigators who have studied the parasites in the human body are agreed that in sections of
the organs they are never seen in the red cells.
The Development of the Parasite in the Bed-Bug.
On December 27th, twelve bugs were fed between 9 and. 10 P.M. on the patient mentioned.
above, and on the 31st one male and three adult females were dissected between 8 A.M. and 12
noon, the midguts and their contents being smeared out on slides and stained by Giemsa's
method. In these films parasites were found in an unchanged condition (Plate I, fig. 7 a) and.
in all stages of development up to the mature flagellates. The leucocytes were seen as indistinct
granular masses, with or without a central deeper stained area, the remains of the nucleus ; such
disintegrating cells may sometimes be seen in the midgut as late as the fourth day, but as a
rule they disappear by the end of the third.
The parasites are ingested by the bug while lying in the polymorphonuclear, eosinphil,
large mononuclear, and endothelial cells, and from a number of earlier observations it appears
that the majority remain unchanged until the second day. While still lying in the disinte--
grating leucocytes they begin to show the earliest signs of development ; the protoplasm
increases in volume, is more granular and instead of staining a faint pink with Giemsa's stain,
now appears blue throughout and contains either one large central vacuole (Plate I, fig. 7 b) or a
number of smaller ones (Plate I, fig. 7 Id,e,f) .
Coincident with these changes the macronucleus becomes enlarged and stains less deeply ;
its central dark chromosome divides into a number of rods which are distributed throughout.
its substance. It may now be either circular in shape or oval with one end more pointed, and
may lie at the periphery or across the centre of the parasite. The micronucleus, still rod like
and staining almost black, increases in size and is usually seen lying towards the periphery of
the cell. Parasites more advanced towards development have a very characteristic appearance ;
their protoplasm has still further increased in amount so that the body of the parasite is made
up of granular blue staining protoplasm. The vacuoles also appear more distinct measuring
from .8μ to in diameter r they are usually circular in shape and vary in number from four to
eight. When deeply stained by Giemsa's method the periphery of these parasites which stains
a much darker blue than the rest of the cell suggests a condensed layer of protoplasm of the
nature of a cuticle. Parasites exhibiting these changes vary in size from 4 μ to 7μ ; some are
oval in shape but the majority are round. In a few the macronuclei have still further increased
in size and show the earliest changes towards division (Plate I, fig. 7 f). A constriction forms.
on the inner side and gradually deepens ; at the same time the chromosomes begin to pass to
the two ends which become rounded off, and on a similar constriction forming on the opposite
side the appearance of a dumb-bell is produced (Plate I, fig. 7 c and fig. 8 f), and later two
daughter nuclei are formed (Plate I, fig. 9 f).
Plate I, fig. 7 c, shows five parasites which have been lying in one leucocyte, and which, as
this has degenerated, have become grouped together; one of the parasites is still in an early
stage of development while the others are much further advanced. Vacuolation at this stage
and later is a marked feature of the development in the bug, many of the parasites containing
four or five vacuoles in close apposition but separated by strands of dark protoplasm.
From a careful study of the films it was seen that after the early stages described above
one or other of two things takes place : (1) the parasites may rapidly pass on to flagellation ;
or (2) what is more important, they further enlarge and by consecutive division of the macro-
and micro-nuclei produce a rosette of from four to eight parasites. Judging from the large
number of these rosettes and groups of elongated flagellates still attached, it appears that the
further increase in size and resulting formation of rosettes is the more usual change that
takes place.
In the enlarged parasites an area staining bright pink and with a darker centre measuring
about . 4 μ ,
d e v e l o p s i n c l o s e r e l a t i o n t o t h e m i c r o n u c l e u s ( P l a t e I ,f
i g .
8 a , b , c , d , f ) .
T h i s
structure which represents the early formation of what has been variously named vacuole-like
area' (Christophers 13) , ' F l a g e l l a r v a c u o l e ' ( L e i s h i n a n 1 4
) , a n d ' E o s i n b o d y ' ( R o g e r s1
5
) r a p i d l y
increases in size and when fully developed is almost circular in shape measuring from 1 μ to 3μ ,
according to the size of the parasite (Plate I, fig. 9 d). When stained deeply with Giemsa's
stain it is seen to consist of a homogenous pink substance in which darker pink strands are
scattered irregularly. It now passes to the surface of the parasite when it ruptures and a small
pink brush begins to protrude directly from it (Plate I, fig 9 a and b). When stained deeply
and examined with a high magnification this brush is seen to consist of a number of delicate
pink strands lying in a pink matrix and in suitable preparations the filaments can be traced.
into the vacuole to one or two dark pink dots in the neighbourhood of the micronucleus ; but
2