2
Series I.—From May 1895, out of a very large number of mosquitos of
many species examined unfed, none contained pigmented cells.
Series 2.— From May 1895, out of a number of brindled and grey mosquitos
fed on healthy persons, none contained pigmented cells.
Series 3.—From May 1895, out of a very large number brindled
mosquitos fed on patients with crescents, pigmented cells were not observed
in any.
Series 4.—From 1896, out of a large number of grey mosquitos fed on
patients with crescents, pigmented cells were not found in any.
Series 5.—In August and September 1897, out of four dappled-winged
mosquitos fed on a case of crescents, pigmented cells were found in three.
Series 6.—In August and September 1897, out of a considerable number
of small dappled-winged mosquitos fed on healthy persons, pigmented cells
were not found in any.
Series 7.—In September 1897, one grey mosquito caught feeding on a
case of mild tertian contained pigmented cells.
Series 8.—In January 1898, out of 30 horse-flies (Tabanus) and some lice
fed on pigeons with halteridium, Labbé, none contained pigmented cells.
Series 9.—Early in February 1898, out of 34 brown brindled mosquitos
fed on a case of triple quartan, none contained pigmented cells,
2. Discovery of Pigmented Cells in Grey mosquitos fed on Larks with Pro-
teosoma.—In February 1898, I was placed by the Government of India on
special duty to prosecute these researches and was given the use of Surgeon-
Lieutenant-Colonel D. D. Cunningham's laboratory in Calcutta for the purpose.
Steps were immediately taken to find again, if possible, the pigmented cells by
feeding different species of mosquilos on blood containing different species of
gymnosporidia. It was found that Calcutta abounded in the grey or barred-
back species of mosquito, which is the filaria-bearing species, and with which
I had already experimented in Series 2, 4 and 7 above. These had uniformly
yielded negative results in Secunderabad when fed on blood containing cres-
cents. Nevertheless, owing to difficulties in the way of obtaining other varieties,
both of mosquitos and of malaria cases, numbers of this kind were again fed
on a patient infected with crescents. Out of 41 of these searched exhaustively
for pigmented cells, not one contained them (Series 10). An unrecorded
number, say 50 more, examined unfed, or, after feeding on healthy persons, gave
similar negative results.
As it was not the malarious season of the year, and as cases of hæmam\ill\biasis
suitable for these experiments were not at all easy to procure, it was thought
advisable to commence work on the so-called malaria parasites of birds.
Accordingly, a crow (corvus splendens) and two tame pigeons infected
with halteridium were obtained ; and on the night of the nth and 12th March
these, with four short-toed larks (calandretta dukhunensis) and six sparrows
(passer Indica), whose blood had not yet been carefully examined, were placed in
their cages, all within the same mosquito netting, and a number of grey mosquitos
of the species I had lately been experimenting with were released within the net.
Next morning, numbers of these insects were found gorged with blood and were
caught in test-tubes in which they were kept alive for two or three days.
On the 13th March I commenced to examine them. Out of fourteen of
them, pigmented cells were at last found in one.