Gr. H. F. Nuttall 
confirmed the observations of Nicolle and his collaborators in that they 
transmitted typhus to a man and monkey by inoculation with crushed 
infective lice. They state that typhus virus is transmitted hereditarily 
in lice. The incubation period in monkeys inoculated with the contents 
of infected lice or their eggs, lasted eight and five days respectively. 
Ussher (19. ix. 1914, pp. 509-510) in Van, Turkey, records that a male 
nurse “subjected himself to infected lice, and promptly contracted the 
disease,” after an incubation period of five days, according to the author’s 
recollection, which would appear to have been untrustworthy or else the 
man was infected before. A five day incubative period is too short. 
Nicolle, Blanc and Conseil (3. xi. 1914, pp. 661-664; 1. xii. 1914, 
pp. 84-121) record two interesting cases of louse transmission of typhus: 
(1) a guardian of a Tunisian penitentiary, since deceased, having doubts 
as to the part played by lice as vectors, and being of an independent 
and experimental turn of mind, surreptitiously placed some lice, taken 
from a typhus patient, upon the neck of one of two workmen who came 
from the outside and lodged in an outhouse apart from the infected 
inmates. The ^experimentally infested man developed typhus on the 
ninth day, whereas the “control” remained well. (2) A laboratory 
assistant was accidentally bitten by an infected louse and developed 
typhus on the 10th day. 
In view of the conflicting results obtained by various investigators 
(see p. 52), the authors sought to determine when the lice become in¬ 
fective. For this purpose they fed lice to repletion upon infected 
monkeys, and, at stated intervals, they crushed 10-40 or more of these 
lice and injected their substance intraperitoneally into test animals 
as follows: (1) eight monkeys and two guinea-pigs were inoculated 
with lice crushed after 1-8 days with negative result. (2) Four 
monkeys and one guinea-pig were inoculated with lice crushed after 9-10 
days and all developed typhus. The periods of incubation observed in 
the case of the last four monkeys were respectively 10, 22, 26 and 
41 days. The authors note that it was a mistake of the American 
observers to discard their non-reacting monkeys as early as the 15th 
to 20th day after inoculation since the incubation period may be longer. 
The faeces of lice fed on typhus blood were found infective by the 
inoculation of animals: 
Faeces collected 
Result of inoculation 
2-10 days after the lice were infected 
.. 1 positive 
6-10 „ „ „ 
1 positive 
3-6 „ „ „ 
2 positive 
7-9 
1 doubtful and 1 negative 
