My first attempts to transmit typhus to laboratory animals, including the smaller species of monkeys, had failed, as had those of my predecessors, for reasons which I can easily supply today.

The discovery that I soon made that the guinea pig was also susceptible to infection made it possible for me, from the third year on, to preserve the virus on this animal.

Of all the problems which were open to me for study, typhus was the most urgent and the most unexplored. We knew nothing of the way in which contagion spread.

Charles Jules Henry Nicole Quotes