9
chromatic dot. One micronucleus is 2μ from the anterior end and. the other about 5 μ , and the
flagellum is inserted near the anterior one. Two chromatic filaments are seen extending from
the vicinity of the macronuclei, and uniting lower down pass into the flagellum. This was the
only flagellate, exhibiting these appearances, and later when discussing the development of the
parasite reference will again be made to it. I was unable to find any parasites in the smears
made from the crops and salivary glands of the bugs.
There can be no doubt from the above description that the Leishman- Donovan bodies had
undergone marked developmental changes in the bed-bug (Cimex rotundatus), the following
being a summary of the nature and order of sequence of these changes. On the second day
after being ingested by the bug the parasites begin to develop, their protoplasm increasing in
volume ; at the same time the macronuclei enlarge and show signs of commencing
division. The
parasites may now either pass on to flagellation, or further growth followed by the consecutive
division of the macro-and micronuclei may result in the formation of rosettes. The single
flagellates enlarge and begin to divide longitudinally to result in oval or spindle-shaped cells ;
while the rosettes after flagellation begin to divide up into separate elongated flagellates. The
oval or spindle-shaped parasites divide repeatedly either by equal or unequal longitudinal
division and result in smaller and more irregular forms. All these changes may be seen in the
bug during the first three days. Still later longitudinal division of the oval and. irregular
flagellates progresses rapidly, so that by the fifth day the majority have become small or
s p i r i l l a - l i k e f l a g e l l a t e s .
As the bugs were dissected at intervals of about 24 hours it was difficult to follow some of
the later stages of the development. For instance, it is probable many spindle-shaped or oval
cells are produced directly from the rosettes, and further the long fully developed flagellates
may be formed from these spindle-shaped. cells. I was also unable to find any evidence to show
that the long flagellates may divide longitudinally, and none of them had the spirilla-like forms
splitting off as described by Leishman.
The small irregular flagellates containing more than one macro-and. micronucleus figured
in Plate II, fig. 6, result most probably from the rapid and irregular division of the oval forms.
produced from the spindle-shaped parasites. Further, it must be remembered that the bugs had
not fed for five days, so that it is quite possible some of the later changes were considerably
modified by the absence of blood.
During the six days the parasites were developing the bugs were kept in an open verandah
where the average temperature was 72° F. From the fact that in cultures the parasites only
develop below a temperature of 75° F., Rogers 13 believes that the majority of patients become
infected with the Leishman-Donovan body during the cold season. He finds from an analysis
of two series of cases in Calcutta, that the disease commenced during the cold or early in the
hot weather. Dr. Dodds Price1 8
a l s o s t a t e s t h a t i n h i s E u r o p e a n c a s e s a n d i n t h e m a j o r i t y o f
his native patients the disease began during the cold weather. From these observations it appears
that the disease usually begins in the cold season, and if; as Rogers states, the incubation period
is probably a long one, it is natural to conclude that the patients were infected months earlier
in the hot season.
As st at ed i n my fi rst report 1 I found t hat t he parasi t es devel oped i nt o fl agel l at es when t he
temperature was between 80° and 82° F. ; and as we do not know even the approximate length
of the incubation period, it seems premature to conclude that the infection can take place only
during the cold season. A large number of experiments with infected bugs kept at different
temperatures are necessary before we can hope to solve this point.
On comparing the development of the parasite in the bug with that seen in cultures in vitro
as described by Rogers15, Christophers13, Leishman and Statham14, it will be seen that though
they agree in many points, they differ considerably in others. Vacuolation of the protoplasm
in the earlier stages of development is seen in both the bug and in the cultures, but it was absent
in the later states in the development in the bug. The chromatic dots which Leishman has
described occurring in pairs in the protoplasm both in the younger stages prior to exflagellation
as well as in the mature parasites were not seen in any of my films. Christophers and Leishman
have described the formation of two or more parasites resulting from the consecutive . division
of the macro-and micronucleus of a single cell, and the latter mentions that these cells may give
rise to three or even four individuals by a process of further sub-division of the macro-and
micronuclei. This process is apparently a marked feature of the development in the bug
resulting in the formation of rosettes of from four to eight flagellates.
In the bug longitudinal division of the round or oval parasites was not seen prior to
flagellation, though in some of the parasites the macronuclei showed evidences of division ; all
the twin parasites had. grown to maturity while lying side by side. This method of multiplica-
tion is therefore entirely limited to the flagellate stage.
In the majority of the spindle-shaped and oval flagellates the micronuclei were seen close up
to the macronuclei, seldom. at the anterior end in the long mature flagellates and spirilla-like
forms, however, the mircronuclei were situated some distance from the macronuclei and about
1 . 5 μ t o 2 µ f r o m t h e a n t e r i o r e n d s . I n t h e c a s e o fT
r y p a n o s o m a l e w i s i
w h e n a p a r a s i t e i s a b o u t
to divide the blepharoplast passes close up to the nucleus, only resuming its final position when
3