THE ENVOY 369 
concept of a living “ contagion ” or infective agent—invisibly 
floating in the air at the time of epidemic pestilences, and com- 
parable with some kind of “insect”. Malaria, for example, 
was all too well known in classical times, and even rustic writers 
such as Varro‘ (116-27 B.c.) and Columella (florwit ca. A.D. 50) 
cuessed that the “insects” abounding in marshes have some 
causal connexion with “fever’’.* (The ancients even used 
mosquito-nets as a prophylactic.) At a much later date 
Lancisi (1718) developed a more coherent and modern theory 
of malarial infection: yet even in his hands it remained nothing 
but an ingenious speculation.’ The true aetiology of malaria 
has become known only in the last fifty years. In Leeuwen- 
hoek’s day both the malarial parasite and its mode of 
transmission by the mosquito were still wholly unknown to 
mankind, and the guesses of his predecessors and contem- 
poraries have really no bearing upon his own discoveries. 
Nobody before Leeuwenhoek ever saw a living protozoon, and 
1 Marcus Terentius Varro (who was no mere husbandman) is particularly 
noticeable because of his antiquity. He is frequently cited, but seldom 
correctly. In all his extant works there appears to be but one passage 
bearing on the aetiology of malaria: and as most editions of his writings 
are rare, and as the passage in question is very short, I may quote it here. 
Discussing sites appropriate for a country house, Varro notes certain places 
to be avoided (such as the banks of a river—apt to be too cold in winter 
and unhealthy in summer) and then adds: ‘‘ Attention should also be paid 
to any marshy places thereabouts ; both for the same reasons, and because 
[they dry up,] certain minute animals grow there, which cannot be detected 
by the eye, and which get inside the body from the air, through the mouth 
and nostrils, and give rise to stubborn distempers.” (Advertendum etiam 
siqua erunt loca palustria, et propter easdem causas, et quod [arescunt,] 
crescunt animalia quaedam minuta, quae non possunt ocult consequi, et per 
aera intus in corpus per os, ac nares perveniunt, atque efficiunt difficilis 
morbos.) Of. Varro, lib. I, cap. XII (Script. Rez Rust., ed. 1543, p. 54 recto). 
The words in square brackets should probably be omitted—arescunt being a 
MS. misreading or dittography of the word following.—Since writing the 
foregoing note I find there is now an excellent English edition of Varro by 
Storr-Best (1912): nevertheless, I let my own translation of the passage 
stand. 
2 The references to malaria in the Latin classics are mostly collected in 
the recent posthumous work of Celli (1925), while the Greek literature has 
been ably reviewed by Jones (1909). 
3 Lancisi actually refers to L.’s discoveries in order to prove the existence 
of such extremely minute animalcules as he himself postulated. Cf. op. cvt. 
p. 46. 
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