52 
Lice and Disease 
Immunity tests were applied in each instance to the animals which 
had recovered 1 . The author concludes that typhus may be transmitted 
both by lice being crushed upon the skin or through the bites of the 
infected insects. 
These experiments of Goldberger’s do not appear entirely convincing, 
and a statement by Anderson and Goldberger (x. 1912, pp. 101-130) 
rather bears out this contention. They mention, namely, that about 
22 % of the monkeys used for experiment possess transient or permanent 
immunity against typhus inoculation. They failed (p. 130) to confirm 
Wilder’s opinion that the virus of typhus is hereditarily transmitted 
in the louse. 
The period of injectivity of lice. Nicolle, Comte and Conseil (1909, 
vide supra) found lice infective, 1-7 days after they had fed on typhus 
blood; Nicolle and Conseil (1911) subsequently infected two monkeys 
with lice after a period of 5-7 days. Wilder (1911) thought he had 
infected a monkey through louse bites after an interval of 7-11 days. 
Anderson and Goldberger (x. 1912, p. 129) thought that in one of their 
experiments they had infected a monkey through l<*use bites after 
a period of 1-4 days. These conclusions appear difficult to harmonize. 
[See the results of further experiments by Nicolle and his colleagues, 
on p. 53.] 
Prowazek (3. xi. 1913, pp. 2037-2040) infected a monkey by in¬ 
jecting the contents of a single crushed louse that had fed two days 
before upon a typhus patient and had been afterwards fed twice upon 
a monkey. The test monkey showed fever on the 12th day after 
inoculation; the blood changes, as also the lesions, agreed with those 
observed in man, there being no other apparent reason why the animal 
died. He found no organisms in the lice. Though much has been 
made of this observation of Prowazek’s in Germany, there was 
practically nothing new in it 2 . 
Sergent, Foley and Yialatte (3. in. 1914, pp. 964-965) note that 
epidemics have occurred frequently in which typhus 'and relapsing fever 
have been observed side by side. The explanation of this is rendered 
obvious by an experiment wherein the authors fed lice from a relapsing 
fever patient upon a man, and unintentionally gave him typhus 3 . They 
1 It may be stated incidentally that immunity cross-tests, in the hands of the authors 
and also of Ricketts and Wilder, established the non-identity of experimentally induced 
typhus and Rocky Mountain fever in monkeys. 
2 S. von Prowazek died 17. n. 1915 from typhus contracted whilst studying the disease 
among Russian prisoners of war at Kottbus [Med. Klinik, xi. 264). 
3 Incubation period of 14 days after the infective lice began to feed daily upon the man. 
