344 
The Discovery of the Coccidia 
I can, into English. I will now give this translation, and will make my 
comments upon the observations afterwards 1 . 
From Leeuwenhoek?s 7th Letter , October 19, 1674. 
The bile of an ox was examined [ i.e. with the microscope] by me on the 1st instant 
[ i.e . 1 Oct. 1674], and therein I beheld some few globules that floated in the liquid; but 
[I saw them] only when I set the bile in a continual motion before my sight, for it would 
else have been impossible for me to perceive the globules in it, owing to their fewness in 
the bile that I was examining. But afterwards, examining the bile of another ox, I found 
that the globules were of a heavier matter than the liquid that they floated in; wherefore 
I drew off the bile from the bottom of the gall-bladder, and then found that there were many 
hundred times more globules in this bile than in that which I had taken from the upper 
part of the gall-bladder; and there were, besides, some corpuscles which, to my eye, looked 
as big as ants’ eggs 2 . These had the figure of an egg [i.e. a hen’s egg], only with this differ¬ 
ence, that whereas an egg is more sharply pointed at one end than at the other, yet these 
corpuscles were equally pointed at both their ends: and moreover these corpuscles were 
composed of globules joined together, and had a yellow colour, except several which were 
somewhat whitish; but notwithstanding, they were so transparent that you could see the 
body of one through that of another. And this transparency making me wonder w r hether 
they were not, in fact, little vesicles filled inside with liquid, I took some of these corpuscles 
out of the bile with a fine hair; and examining them on the hair, I perceived two which 
seemed to be bent in, just as though you had filled a bladder with air and then put your 
thumb on it, so as to make a dent in it: whereupon I was the more firmly persuaded that 
these corpuscles were filled with some sort of liquid. Afterwards, examining more biles 
from oxen, I found them the same as before; only with this difference, that one bile would 
contain more of the oval corpuscles than another. 
In the bile of two calves I find, furthermore, some very little globules floating, and very 
many irregular particles of divers forms; among others, some like little floating clouds, all 
consisting of very little globules joined together. On seeing these irregular aggregated 
particles, I judged them to be joined or stuck together through no other cause than because 
the bile had got cold, and was without motion. In the bile of a third calf there were a few 
oval corpuscles. 
Moreover, in the bile of sucking lambs I find there are very little globules, and some, 
though very few, bright particles, which are a bit bigger; besides irregular particles, of 
divers figures, and also composed of aggregated globules. The bile of a yearling sheep I find 
to be like that of sucking lambs, only with this difference, that in this bile there are also 
oval corpuscles of the bigness and figure of those that I remarked in ox-bile. 
I have examined the bile of two young rabbits: that of the first was inclined to a purple 
colour, and in it I beheld very many globules, and irregular particles made up of aggregated 
globules, which were of various red colours 3 : and this diversity of colour I conceived to 
be due to no other cause than that some of these compound particles, being made up of 
more globules, were denser than the rest. In the other bile the irregular particles were 
fewer, but there were more globules and the colour was a light red. 
1 Words in square brackets are added by me in order to preserve the sense or in explanation 
of expressions used in the original. 
2 This is a usual form of expression with Leeuwenhoek. He means that the objects looked, 
under the microscope, about as big as “ants’ eggs” look to the naked eye. At a later date he 
published a remarkable account of ants, from which it is clear that he was well aware that the 
ant’s “egg” is not really an egg, but a pupa. See Letter 58, Sept. 9, 1687. 
3 It seems probable that these globules were red blood-corpuscles. Leeuwenhoek had described 
these—from his own blood—in another letter written earlier in the same year (April 7, 1674). 
