0. Dobell 
343 
describe coccidia, in a recognizable manner, in any printed work. It is not 
my aim, in the present paper, to dispute his claims in this respect: but I hope 
to be able to show that another and a greater man discovered the “ovate 
corpuscles” long before Hake was born; and not only discovered them, but 
left a record of his observations—a record which was written nearly 250 years 
ago, but which has never yet, I believe, been read aright, and has certainly 
never yet been printed. 
It is well known that the celebrated Dutch microscopist Antony van 
Leeuwenhoek (1632-1723), the discoverer of the Protozoa, never published 
his earliest letters—though his real reasons for not doing so are still unknown. 
In both the Dutch and the Latin printed editions of his collected works the 
first epistle is that which he himself called his “28th Letter” (April 25, 1679): 
and a note by the publisher informs us that “the previous 27 letters written 
by the author, he could not hitherto resolve to make public by printing: and 
thus the 28th is the first that is here printed 1 .” Yet these early letters are 
not lost. The original manuscripts, written in Dutch, have been carefully 
kept 2 by the Royal Society, to which body they were addressed: and as they 
are all dated, it is not difficult, for anybody who will take the trouble, to 
ascertain their true sequence and the distinguishing numbers which Leeuwen¬ 
hoek himself probably assigned to each. Moreover, some of these letters have 
been partly printed, in the form of English or Latin abstracts, in the early 
volumes of the Philosophical Transactions : but these are fragmentary and 
incomplete, and convey a very imperfect idea of the originals; while at least 
eight have never been printed at all, and their contents have, to the best of 
my belief, remained entirely unknown to the scientific world from that day 
to this. 
During the last few years I have made a careful study of these early un¬ 
published letters, and I have found many very interesting observations 
recorded in them. I hope to be able to say more about these letters on a 
future occasion; but in the present note I wish to direct special attention to 
only one of them—a letter (entirely unpublished hitherto) which is dated 
October 19, 1674, and which is, according to my reckoning, the “7th Letter” 
in the whole series. It is not very long—not long, that is to say, for Leeuwen¬ 
hoek—for it consists of only five large and rather closely written pages. It is 
addressed to Henry Oldenburg—then Secretary of the Society—and contains 
a number of microscopic observations on bile, fat, sweat, etc. The observa¬ 
tions on bile are in some respects so remarkable that I think no apology is 
needed for publishing them. As Leeuwenhoek’s Dutch would not be readily 
intelligible to most modern scientific readers, I have—though not without 
reluctance—translated the passage in question bodily, and as literally as 
1 See the Dutch works of Leeuwenhoek, II Deel, ad init. (Register der saaken). 
2 I should state that there are three exceptions; for the first letter of all, and two others which 
I believe to have been the 17th and 27th, are missing. The first was partly printed, however, in 
the Philosophical Transactions for 1673. The others are, I believe, wholly and irrecoverably lost. 
