Ronald Ross Nobel Lecture

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the disease curable by the medicine, namely malarial fever; and the works of

these writers, especially Torti, who without possessing thermometer or mi-

croscope accurately described the intricate course of the disease, are among the

most admirable works of medical science. At the end of the seventeenth and

the beginning of the eighteenth century Morton and Lancisi elaborated an-

other important conception, that the disease is produced by some poison

which enters the body from without; and the latter especially clearly under-

stood what may be called the great law of malarial fever that it is connected

with stagnant water on the ground. The next great advance was made in the

middle of last century by Meckel, Virchow, Planer, Arnstein, Frerichs, and

others, who discovered that the disease is characterized by the presence in the

blood and some tissues of a peculiar black granular substance, the malarial

pigment or melanin; and this observation led directly to the great discovery

of Laveran in 1880, that the melanin is produced within multitudes of minute

amoeboid parasites which live within the blood corpuscles of the patient - a

discovery which not only illuminated the whole subject of malaria, but, by

opening a new department of parasitic pathology, has put the name of Lave-

ran in the place of honour beside those of Pasteur, Lister, and Koch.

The work of Laveran and of those who followed him affords one of the

most beautiful and useful chapters in the whole book of science; and I wish

that it were possible to deal with it here at length. We owe to Danilewsky,

Theobald Smith and others the discovery of similar parasites in the blood of

many vertebrates, and to Laveran and Golgi the determination of several im- 

portant laws concerning the whole group of these organisms. Marchiafava,

Celli, Mannaberg, Metchnikoff, Canalis, Antolisei and many others added

important details; Kelsch and Bignami made minute clinical and pathological

studies; Romanowsky discovered the best method of staining the parasites;

Gerhardt and others produced infection by inoculating the blood of patients

into healthy persons; and Richard, Councilman, Vandyke Carter, Osler,

Plehn and numerous other skilled observers confirmed those results in many

parts of the world. The principal conclusions reached by this mass of investiga-

tions are as follows :

(1) That Laveran’s parasite is the cause of malarial fever.

(2) That it is a sporozoon belonging to a group probably allied to the Coc-

cidiidae, of which other members are found in birds; and that somewhat sim-

ilar but more distantly related haemocytozoa are found in other vertebrates.

(3) That the organisms propagate in the blood by spore formation.

(4) That there are probably at least three varieties of the human parasites,

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which cause respectively the quartan, the tertian, and the irregular (pernicious

or aestivo-autumnal) fevers.

(5) That the paroxysm of fever commences with the release of the spores.

(6) That with all varieties of the parasites, there are certain forms which do

not produce spores, but which, shortly after blood containing them is drawn

from the host, emit certain singular motile filaments; and that the nature and

functions of these forms still required further investigation.

3. The problem of the mode of infection. 

But even after all these fine discoveries,

there still remained for solution a problem of the greatest difficulty and of the

greatest importance. We had discovered the pathogenetic organisms of ma-

larial fever, and had studied them and their effect with the greatest care. This

was much, but not all; it sufficed for the treatment of individual cases; but not

for the prevention or extirpation of the disease on a large scale. For this we

were obliged to seek a wider knowledge: the parasites occur in the human

blood - but how do they arrive there? On this scientific question turned the

whole prophylaxis of malaria - a subject the importance of which in connec-

tion with the future development of many of the richest portions of the

world’s surface I need not enlarge upon. Ignorant of the route of entry, we

could rest our prophylaxis only upon an unsatisfactory empirical basis; cog-

nizant of it, we might hope to stamp out the plague even in its most redoubt-

able haunts. It is my privilege in this lecture to describe particularly the steps

by which this great problem has at length received its full solution.

In what manner precisely does the malarial infection reach the human

blood? From early times certain cardinal facts regarding the disease have been

known to us and have limited the area of investigation regarding this question.

It has been recognized, first that malarial fever is essentially an endemic disease

- that is, that it does not easily spread from man to man independently of local-

ity, as do for instance, small-pox or plague; secondly that it adheres especially

to warm localities where there is much stagnant water, such as marshes. Upon

these facts, themselves perfectly true, numerous hypotheses have been con-

structed; notably the one, dating from the times of Lancisi and Morton, that

the disease is due to miasmata exhaled from the stagnant water whence in-

deed the word malaria has originated; and later the allied theory of the telluric

miasm, according to which the soil possesses a poisonous effluent so powerful

at certain spots that it can there produce fever in man. It was even thought that

when the surface of the ground is disturbed, this effluent escapes like a gas,

infecting all those who live in the vicinity. These speculations afford an in-

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