Most of the doctors in the Tunisian administration, especially those in country districts, contracted typhus and approximately one third of them died of it.

I finally demonstrated that typhus infection is not hereditary in the louse.

It did not seem likely that I was destined to undertake research on typhus.

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.

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.

I was less successful in my attempts to effect preventive vaccination against typhus by using the virus and in trying to produce large quantities of serum using large animals.