The record-union., 1899-10-16

ton in vitro. On the other hand,
Laveran, Danilewsky and Mannaberg
supposed them to represent the highest
development of the organisms, while
the last writer thought that they were
meant for an exogenous saprophytic
xistence-without, however, suggest
ing the mode of their escape In 1894
Manson concluded that the gametocytes
are intended to continue the species
outside the vertebrate host; and that
they escape into the stomach of a sue
torial insect, and then give rise to
flagellulae-as he considered the micro
gametes to be-which in turn develop
in the tissues of the insect He founded
these views chiefly on the fact that the
microgametes escape from the gameto-
cyte only after abstraction of the blood
from the vertebrate host Laveran had
already surmised that the mosquito
is the alternative host of the human
parasites; and Manson now claimed the
mosquito as the suctorial insect re-
ferred to.
MAJOR ROSS EXPERIMENTS.
Early in 1895 I attacked the subject
experimentally in India, on the lines
laid down by Manson. Owing to the
| difficulty of the investigation and to
! the use of wrong species of mosquitoes,
/ failed for more than two years in
reaching positive results. In August,
1897, however, on employing two spe-
cies of anopheles fed on patients con-
! tanning the crescentic gametocytes, /
| found the Zygotes in various stages Of
| growth attached to the wall of the in
sect's stomach. My work was now in
! terrupted; but next year I succeeded in
| following out the life-history of the
! zygotes of one Of the parasites of birds
! in their development in Culex pipiens.
! The zygotoblasts were found in the
| salivary glands of the mosquitoes; and
| lastly in July, 1898, succeeded in in
! fecting a large number of healthy birds
| b ythe bites of infected insects.
Meanwhile QS9S) MacCallum had dis
covered the true nature of the micro
| gametes by actually witnessing the
sexual act in vitro, while Metchnikoh
and Simond had found microgametes
also in Coccidium oviforme and c.
salimandrae; so that the exact rela-
tionship between the gametocytes in
the blood of the vertebrate Qntermedi-
ary) hosts and the zygotes found by
me in the mosquitoes definite hosts)
became quite evident.
FACTS ESTABLISHED.
My results were published by Man
son in August, 1898, and were con-
firmed by Daniels of the Malaria Com
mission of the Royal Society, in De-
/
my observations to other species of the
/ group, work, however, which l was
unable to undertake. In November
and December, 1898, Grassi, Bignam
and Bastianelli cultivated two of the
human parasites in third species ol
! anopheles, A. claviger, Fabr., and sue
ceeded in injecting several healthy per
sons Shortly afterward Koch con-
firned the principal observations which
had been made.
If we can exterminate the malaria
bearing species of mosquito in a local
! ity we may expect to prevent the
propagation of the parasites there;
trust, therefore, that these investiga-
tions will not remain without practical
results.
CAUSE AND PREVENTION OF
MALARIA.
In Mature" of August 10th we find
/ the report of Major Ross to the Sec
retary of the Director General Of the
India Medical Service, dated at Cal
cutta, February 16 1899. Major Ross
says:
1 have the honor to address you, on
completion of my term of special duty
for the investigation Of malaria, on the
subject of the practical results as re-
CARDS the prevention of the disease
which may be expected to arise from
my researches; and I trust that this
letter may be submitted to Government
/ if the Director General thinks fit.
1t has been shown in my reports tc
you that the parasites of malaria pass
a stage Of their existence in certain
species of mosquitoes, by the bites OF
which they are inoculated into the blood
of healthy men and birds. These obser-
vations have solved the problem-pre-
viously thought insolvable-of the mode
of life of these parasites in externa
nature.
My results have been accepted by DIR
Laveran, the discoverer of the parasite.
grated the mosquito theory of malaria
by DR.. Nuttall of the Hygienic Insti
tute of Berlin, who has made a specia
study of the relations between insects
and disease and, I understand, by M
lMetchnikoff, Director Of the Laboratory
of the Pasteur Institute in Paris. Late.
ly, moreover, DR.. c. w. Daniels of thC
Malaria Commission, who has beer
sent TO study with me in Calcutta, nas
confirmed my observations in a specia
report to the Royal Society; while, last
ly, Professor Grassi and Drs. Bignan
and Bastianell of Rome have beer
able, after receiving specimens anC
copies of my reports from me- to re-
peat my experiments in detail and t.
follow two of the parasites of human
malaria through all their stages in 6
species of mosquito called the Anoph
eles claviger
HOW MALARIA COMES.
It may, therefore, be finally accepted
as a fact that malaria is communicated
by the bites of some species of mos
quito; and, to judge from the genera
laws governing the development of par
asitic animals, such as the parasites O.
malaria, this is very probably the onl,
way in which infection is acquired, il
which opinion several distinguished
men Of science concur with me.
In considering this statement it /:
necessary to remember that it does no
refer to the mere occurrences of feve.
to which people previously infected arr
often subject as the result of chill, IA
tigue and so on. When l say that ma
laria is communicated by the bites o