346 
The Discovery of the Coccidia 
the liver of a sheep. They were also known—at a later date, at all events—- 
to Leeuwenhoek; for the anatomist Bidloo (1698) addressed a small work 1 
to him in which they were described and figured in some detail, and Leeuwen¬ 
hoek himself afterwards wrote a letter on the “Worms observ’d in Sheeps 
Livers” to the Royal Society, who published a short English abstract of it 
in their Transactions in 1704 (Letter dated November 3, 1703, Phil. Trans. 
xxiv. 1522: not in Latin or Dutch collected works). 
But I am not now concerned with the discoveries in the bile of oxen and 
sheep save in so far as they throw light upon the objects which Leeuwenhoek 
found in the bile of the rabbit. He says that these objects were like those 
which he saw in the bile of the ox; and consequently, if my interpretation 
be correct, they were like the eggs of a liver-fluke. Now as everybody knows, 
the gall-bladder of the rabbit very frequently does contain bodies which are, 
superficially, extremely like the eggs of Fasciola hepatica —namely, the oocysts 
of Eimeria stiedae Lindemann. In size, shape, and general appearance these 
are so like eggs that they were long known—before their nature was ascer¬ 
tained—as “egg-like corpuscles” or “oviform psorosperms.” Davaine (1860), 
for example, devoted considerable space to the discussion of these structures 
and concluded that they were probably “the eggs of helminths”: and a direct 
proof that they are not the eggs of worms was not obtained until long after¬ 
wards, when it was shown that they are the cysts (oocysts) of a sporozoon 
living in the bile-canal system within the substance of the liver. E. stiedae 2 
is now known to every elementary student of zoology, but our knowledge of 
it, and of its life-history, was acquired only after many years of study, and 
by the labours of many men. It is unfortunate that Leeuwenhoek said so 
little about what he found in the rabbit’s bile: but his bare statement that 
the “ bodies ” in it were like those which he found in oxen—of which he gives 
an easily recognizable description—suffices, in my opinion, to place the matter 
beyond all reasonable doubt. Anybody who will take the trouble to examine 
the contents of the gall-bladders of a few rabbits can readily confirm his 
observations. 
It will be noted that Leeuwenhoek says he found the “oval corpuscles” 
in the bile of one old rabbit out of three examined; but that he found none 
in two young ones. He does not say whether the rabbits were wild or tame, 
but one may perhaps infer that they were wild ones which had not long been 
kept in captivity; for tame rabbits are often more heavily infected, and his 
observations seem to indicate that he was dealing with comparatively clean 
stock—-some of the old ones but none of the young having acquired infection. 
But the numbers are obviously too few to warrant any definite conclusions 
1 An English translation of this memoir was incorporated by Hoole in his Select Works of 
Leeuwenhoek, vol. i, part 2, 1798. There is also a Dutch version, published at Delft in 1698; 
but this last I have not seen. The Latin version is also to be found reprinted in Bidloo's Opera 
Omnia Anatomico-chirurgica, Lugd. Bat., 1715. 
2 The parasite is commonly called “ Coccidium oviforme ” or “(7. cuniculi ” in the elementary 
text-books. 
