PULCE Microphotography of the female of the pulce of the Indian rat; Xenophilla cheopis; that it infests the rats and other roditori and transmits through these the bacillus of the plague to the man. The existence of the parasite was a discovery of dottor Paul Louis Simon; colonial doctor of tuppe the correspondent in India from the Pasteur Institute. Simon discovered so the way of transmission of the plague in 1898.