56 
Lice and Disease 
The foregoing instances, illustrating the part played by lice in 
relation to typhus epidemics, will suffice for our purpose. Similar 
experiences have been reported from Russia and Serbia. 
7. Demonstration of the Practical Results of Prophylactic Measures 
BASED ON THE KNOWLEDGE THAT LlCE CONVEY TYPHUS. 
The knowledge gained regarding the part played by lice in the 
propagation of typhus, led naturally to the institution of prophylactic 
measures directed against lice. The results have been most striking 
in Tunis, as is shown by the published figures given by Nicolle and 
Conseil (20. i. 1915, pp. 18-20; also referred to by Nicoile, 14. iv. 1915, 
p. 160). The preventive measures produced a great fall in the number 
of cases following on the year 1911, as follows: 
Typhus fever incidence in Tunis. 
Year 
Number of cases 
1909 
856 all indigenous 
1910 
148 „ 
1911 
180 „ 
1912 
22 „ 
1913 
6 
1914 
3 all imported 
1915 
0 
Owing to the war, no evidence as striking as that tabulated above 
is at present available from any other part of the world. The evidence 
affords a complete demonstration of the efficacy of measures directed 
against lice which are the only known vectors of typhus. 
8. Mote on the Virus of Typhus. 
A perusal of the literature on typhus shows that there is no general 
agreement as to the nature of the virus. Typhus is one of those diseases 
in which the supposed cause has been repeatedly discovered in the 
course of many years. Of recent writers some claim that the causative 
agent is a cuitivatable bacterium, others that it is an undeterminable 
microorganism which cannot be cultivated, others that it is a Protozoon, 
others again regard the supposed causative agent of certain authors 
typhus may be conveyed through the atmosphere is of course an old belief, similar to 
that which prevailed formerly in respect to malaria and yellow fever, both of which are 
mosquito-borne. Of recent authors, Kraus (m. 1915, p. 314) and Bujwid (v. 1915, p. 531) 
still cling to this old belief. Proof is lacking that the virus of typhus occurs in the sputum. 
