June 13, 1912] 
NATURE 387 
referred to the brilliant discovery of the parasite by 
Sir Wm. Leishman, R.A.M.C., and of the discovery 
of the flagellate stage by Major Rogers, I.M.S. It 
was at this stage of our knowledge of the parasite 
that, the lecturer said, he began his experimental 
work in 1905, and a detailed description was then 
given of how this problem was attacked, and the 
results which have followed this work during the | 
last seven years. There were two main theories as 
to how the parasite leaves man’s body in order to 
undergo its extracorporeal flagellate stage. Sir 
Patrick Manson had suggested that the parasite was 
discharged from ulcerated surfaces, either cutaneous 
or intestinal, and that it was then ingested by some 
foul-feeding fly. Against this hypothesis, however, 
was the fact that the parasite would not flagellate in 
any medium containing bacteria. Two years ago 
the lecturer had fed a large number of bred house- 
flies (Musca nebulo) on fresh splenic juice, and had 
found that the parasite disappeared from _ the 
alimentary tract of the fly in a few hours; it was 
difficult, then, to understand how the parasite could 
be transmitted in this way. 
The other hypothesis, first advanced by Major 
Rogers, and later by Major Christophers, was that 
the parasite was ingested by some _ blood-sucking 
insect. In order, however, for this to take place it 
was necessary for the parasite to be present in the 
circulating blood of an infected person. Colonel 
Donovan, I.M.S., Major Christophers, I.M.S., and 
the lecturer had no difficulty in finding the parasite 
in the circulating blood of practically every case of 
kala-azar. The lecturer also pointed out in 1907 that 
in certain stages of the disease, namely, severe 
dysenteric attacks, the parasite could be found in 
large numbers in a drop of finger blood. Captain 
Patton then went on to describe how he fed Pedi- 
culus capitis, P. vestimenti, Culex fatigans, Neo- 
cellia stephensi, Stegomyia sugens, and Ornithodorus 
Savignyi on cases of kala-azar in the peripheral blood 
of which there was a large number of parasites, 
but was unable to observe any developmental 
changes undergone by the parasite in these insects. 
He next described his feeding experiments with the 
Indian bed-bug Cimex rotundatus, and pointed out 
that he was able to trace the parasite from its un- 
changed state in a leucocyte in the stomach of the 
bug up to the formation of the mature flagellate 
stage. In twelve bugs which had only fed once on 
a patient, and which were all dissected by the fifth 
day, he was able to confirm these earlier observa- 
tions. As he was then unaware of the probable 
final stages in the development of the parasite, the 
bugs were not kept long enough. The failure to 
obtain a massive infection with the bug when fed 
on a case in the peripheral blood of which there 
were immense numbers of parasites was extremely 
disappointing, and it was felt that there was some 
factor in connection with the development of the 
parasite in the bug which had yet to be discovered. 
Assuming that kala-azar is an insect-borne disease, it 
is a remarkable fact that it has scarcely, if at all, 
spread outside Madras. In order to explain this 
curious epidemiological truth, Captain Patton came 
to the conclusion that, in addition to the small 
number of parasites which are found in the peri- 
pheral blood in the majority of cases, there was some 
natural obstacle which came in the way of the para- 
site completing its life-history in the bug. Further 
work on kala-azar was then abandoned, and the 
study of insect flagellates of the genus Herpetomonas 
taken up. As a result of these studies, Captain 
Patton was able to show not only how several insects 
containing these flagellates became infected, but also 
NO. 2224, VOL. 89] 
| patience. 
pointed out that they had three phases in their life- 
histories—pre-flagellate, flagellate, and _ post-flagel- 
late—and that in the majority of instances insects 
become infected by ingesting the post-flagellate stage. 
He then gave a detailed description of the life-history 
of Herpetomonas muscae-domesticae and H. culicis. 
As a result of this work he came to the conclusion 
that the parasite of kala-azar, in order to be trans- 
mitted to man, must pass back to its post-flagellate 
stage. He directed attention to the fact that almost 
every blood-sucking insect was infected with these 
natural flagellates, and that in order to investigate 
the kala-azar problem it is imperative for the observer 
to have first-hand knowledge of these insectan forms. 
Further, by studying H. culicis, he found that blood 
| had an injurious effect on the flagellate stage of the 
parasite, and this has led to the remarkable dis- 
covery that if a bug contains the flagellate stage of 
the parasite of kala-azar, this stage is destroyed 
within twelve hours when the bug again feeds, either 
on man or on a monkey. He further found that if 
the bug, which contains flagellate stages, is not fed 
again, the parasites by the eighth, ninth, and tenth 
days pass on to their post-flagellate stage, and finally 
round up in the stomach of the bug by the twelfth 
day. His previous failures to find a massive infec- 
tion in the bug or to observe the rounding up of the 
parasite were obviously due to the bugs having been 
repeatedly fed, and not being kept long enough after 
their last feed. 
This observation is of extreme importance, because 
if we are to attempt to try and infect a susceptible 
animal by means of the bug, it would be futile to 
feed infected bugs on the animal before the post- 
flagellate stage had been formed. Captain Patton 
believes that the destruction of the flagellate stage 
of the parasite by fresh blood is the natural obstacle 
referred to above. It would at present appear that 
the bug only becomes infected when it feeds on a 
case in the peripheral blood of which there are a 
large number of parasites, and it can only become 
infective if the interval noted above is obtained for 
the parasite to complete its development. 
Captain Patton then gave a short description of 
his recent work on Oriental sore in Cambay, and 
stated that he had only succeeded in obtaining the 
development of the parasite in the bed-bug. He 
believed that his failures to transmit this parasite to 
man by the bite of the bug were due to the fact 
that the bugs used in the experiments were re- 
peatedly fed, and that an interval for the parasite to 
complete its development was not allowed. He was 
at present carrying out further transmission experi- 
ments with the parasite of Oriental sore, and he 
hoped, in the light of his recent discoveries, to trans- 
mit this parasite by the bite of the bed-bug. 
He fully realised that the conclusive proof that the 
bed-bug is the transmitter of the parasite of kala- 
azar was still wanting. Unfortunately, at present it 
is impossible to infect any known animal with this 
parasite; he would therefore ask those who would 
be ready to criticise his worl to exercise still further 
>. The investigation of the problem of the 
method of transmission of the parasite of kala-azar 
bristles with difficulties, but he believed that a dis- 
tinct advance in the right direction had now been 
made. He was at the present time repeating all his 
experiments with blood-sucking insects by feeding 
them once on a case of kala-azar in the peripheral 
blood: of which there were large numbers of para- 
sites, so that all the different kinds of insects utilised 
would certainly ingest many parasites. He hoped in 
this way conclusively to prove that the parasite will 
only develop in the bed-bug. He had in this wap 
