Ronald Ross Nobel Lecture

    R E S E A R C H E S   O N   M A L A R I A

89

of station to which my family and myself had been subject; and if I were now

compelled to return to Secunderabad, I should not be able later to pay for my

passage to England. Moreover, both Daniels and Rivenburg were now leav-

ing me, and it was evidently foolish to expect any further assistance in India-

much more that of a trained entomologist, which I especially required for the

completion of my work on human malaria. I therefore determined to leave

India forthwith and to return to England, trusting to fortune to give me an

opportunity for finishing the investigation in a manner which I thought suit-

able. I mention these personal details as I have been blamed for leaving India

at that moment.

Before doing so, I urged upon Government the importance of taking active

measures for the prevention of malaria in accordance with my observations.

Besides advising the strict use of mosquito-nets for a personal prophylaxis, I

urged especially a campaign against mosquitoes as the best measure for towns

and cantonments, particularly against the dappled-winged mosquitoes, which

I said breed principally in water on the ground. My letter was published

later

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, and I hope that the advice will soon begin to be taken.

I had also written a brief abstract of my work dated the 31st December,

1898. This was presented by Laveran to the Académie de Médecine on the

24th January, 1899, and was published soon afterwards

55

. In this paper my

obligations to Manson and Laveran were acknowledged, I hope, in the full

manner which honourable science demands. I wrote :

"Pour éviter tout commentaire erroné, qu’il me soit permis de déclarer ici

que mes travaux ont été entiérement dirigés par Manson, et que j’ai eu l’as-

sistance de ses conseils et de son influence à toute occasion; je dois aussi re-

mercier le Dr. Laveran de m’avoir envoyé ses avis si autorisés. Quand, en mai

dernier, je lui envoyai des spécimens de mes corps pigmentés du moustique,

il reconnut immédiatement la vraie nature de ces éléments."

And I added in conclusion,

"Je considère comme probable que la malaria est communiquée á l’homme

uniquement par les morsures des moustiques et peut-être d’autres insectes."

21. England (March-July, 1899). Foundation of the Liverpool School of Tropical

Medicine. 

On the voyage to England (February 1899) I had full time to con-

sider the present condition of our knowledge about malaria, especially in rela-

tion to the all-important subject of prevention. It was almost certain that in-

fection is caused solely by the bites of insects - but of what insects only? My long

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negative work had almost proved that the commonest Indian mosquitoes, the

grey and brindled genera, do not carry aestivo-autumnal infection, at least. On

the other hand, it was certain that two species of dappled-winged mosquitoes

in Secunderabad, and one species in Rome, do carry it; while, if Bignami’s

observation was to be trusted, the last species carries also the mild tertian infec-

tion. But Secunderabad and Rome are not the whole world; even in Bengal,

Daniels and I had not succeeded in infecting dappled-winged mosquitoes. The

question as to which species do or do not carry malaria might prove to be a

very complex one, not to be solved only by a few local experiences; there

are probably hundreds of species of mosquitoes in the world, each of which

would have to be tested unless we could find some good reason for limiting

the enquiry. I therefore sought for some such reason, and found one. For cen-

turies it had been known that malaria is connected with stagnant water on the

ground - not with water in the pots, tubs, and tanks which abound close to all

habitations, but with marshes and pools on the surface of the earth. Again

malaria was known to increase every year at the rainy season, and subsoil-

drainage was known to mitigate if not remove the disease. Hence it was ex-

tremely probable that the insects which carry malaria breed only, or chiefly, in terrestial

water. 

For years we had assumed that the disease is caused by organisms which

spring from marshes. We had been partially right, but not wholly right; it is

not the infective but the infecting organism which springs from the marsh -

not the germ but the carrier of the germ. Now, referring to mosquitoes alone,

which varieties of these insects breed only or chiefly in terrestial waters? I re-

membered my frequent observations on this point (sections 14, 15, and 19).

The grey and brindled mosquitoes breed chiefly in tubs and pots in India; but

the dappled-winged mosquitoes breed in pools on the ground. 

Now it was only these

last which, hitherto, had certainly been connected experimentally with ma-

laria.*

What a weapon for good was now placed in our hands! Hitherto when we

wished to remove malaria we were obliged to drain a whole area, recognizing

only that all terrestial waters seemed to be dangerous. Now we should be able

to go to a place and to point out the actual pools which cause the disease, by

showing that they contain the larvae of the culpable insects. The expense of

dealing only with these would be much less.

Shortly after my arrival in England in March I learnt something about the

zoological classification of mosquitoes from Mr. E. E. Austen of the British

* This reasoning was by no means obvious or even known until after our work at Sierra

Leone. In temperate climates grey mosquitoes (Culex) also breed often in terrestial water.

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