G . H. F. Nuttall 
57 
as merely representing degeneration products of the host’s cells. Whereas 
it has been claimed by some that the virus is capable of traversing a 
bacterial filter others deny that this is the case. It appears inexpedient 
therefore to dwell further upon the matter in this paper. Those who 
may desire to study the literature on the subject are referred to the 
more recent publications of Ricketts and Wilder (1910), Prowazek 
(1915), Nicolle, Blanc and Conseil (1914). Bodies called Rickettsia 
prowazeki are regarded as the cause by Rocha-Lima (1916 and before), 
Topfer (1916), Topfer and Schiissler (1916), Noeller (1916). The 
Bacillus typhi-exanthematici is regarded as the cause by Plotz (1914), 
Olitsky, Denzer and Husk (1916), and Paneth (1916). Supposed 
Protozoa have been described by Stempell (1916). The Diplobacillus 
exanthematicus is regarded as the cause by Rabinowitch (1914-16). 
Penfold (1916) describes a Micrococcus. Proescher (1915) describes 
minute Diplococci and Diplobacilli as present in the endothelial cells 
of the human subject. 
Some of these supposed causative agents have also been found in 
lice, either in infected or non-infected insects. Rocha-Lima denies 
that Rickettsia is ever found in normal lice, and his followers agree 
with him; on the other hand Rocha-Lima states that minute bodies, 
morphologically similar to Rickettsia, occur in uninfected lice, but that 
they differ in not undergoing multiplication in the cells of the insect’s 
midgut. 
II. RELAPSING FEVER AND ITS CONVEYANCE BY LICE. 
1. General Considerations. 
It has already been noted that epidemics of typhus and relapsing 
fever may occur side by side as was first clearly recorded in Ireland in 
1739, and that the two diseases agree in respect to their epidemiology. 
Both diseases were much more prevalent in former times. 
The geographical distribution of relapsing fever is similar to that of 
typhus, it is also a disease of cool and temperate climates, but it is not 
recorded from as many countries by Hirsch (1881, p. 417) and Clemow 
(1903, p. 364). In Europte, it occurs in Great Britain and Ireland, 
Belgium, Germany, Austria, Russia, Finland, Bulgaria and on islands 
in the Mediterranean. Like typhus, it is rare in Norway and Sweden. 
There are no records of it from Switzerland, France 1 , Italy and Spain 
1 It has occurred among soldiers in the present war as an army surgeon informs me. 
