332 LEEUWENHOEK AND HIs “ LITTLE ANIMALS ”’ 
Taffeta (formerly taffety or taffata—a word of Persian 
origin) is a name now applied to various coloured fabrics of 
wavy lustre: but in earlier times it denoted a silken cloth of 
uniform texture—when black, much used for mourning. It 
should be remembered that Leeuwenhoek speaks here not 
only as a microscopist but also as a draper; and he therefore 
meant that he could see human red blood-corpuscles under his 
microscope just as clearly as he could see sandgrains scattered 
on a piece of the smooth black silk he sold in his shop. The 
more I consider these words, the more am I convinced that 
nobody could ever have thought of such a simile unless he 
had seen red corpuscles under dark-ground illumination. 
Their appearance by transmitted light is wholly different, and 
could never suggest such a comparison. To my mind these 
words furnish an almost conclusive proof that Leeuwenhoek’s 
“particular method of observing very small objects” was 
some simple system of dark-field lighting, used in combination 
with his ordinary microscopes. It is idle to speculate on how 
he may have achieved this result : it is sufficient to note that 
such a supposition will easily explain all his otherwise inex- 
plicable observations. (It readily explains, for instance, how 
he was able to see flagella and cilia and spirochaetes and 
micrococci with a magnification of only some 200-300 dia- 
meters.) But as he himself would say, “I hand this notion 
over to others.” 
Leeuwenhoek’s apparatus for viewing the circulation in 
the tail of an eel was fully described and illustrated by 
himself.’ It is a peculiar instrument, designed for a special 
purpose, and not his “‘ microscope”? proper—though it has 
more than once been figured as such by later writers. I need 
not consider it here. I may note, however, that one of these 
instruments is now in the Leyden Museum (with some lenses 
made and mounted for it by himself, and a copy by another 
maker). Leeuwenhoek’s own figures” show that he sometimes 
used the lenses of his “ microscopes’”—mounted between two 
oblong metal plates, as already described—in fitting up this 
1 Letter 66. 12 January 1689. To the Royal Society. Printed in Dutch 
and Latin works, but not in Phil. Trans. The original is preserved among 
the Boyle MSS. of the Royal Society. 
* See especially fig. 8, on the plate accompanying this letter. 
