The original quote, according to my 1963 Brewer's, is from 'Poetry:a Rhapsody' by Dean Swift, author of 'Gulliver's Travels'.
'Hobbes clearly proves that every creature
Lives in a state of war by nature;
So naturalists observe a flea
Has smaller fleas that on hm prey,
And these have smaller fleas to bite 'em,
And so proceed ad infinitum.'