152 
NOTES ON RICKETTSIA\ 
By EDWARD HINDLE 2 , 
Professor of Biology, School of Medicine, Cairo. 
{From the Quick Laboratory, Cambridge, and the Biological Dej)t., 
School of Medicine, Cairo.) 
Introduction. 
Among the recent advances in our knowledge of the aetiology of human dis¬ 
eases, one of the most interesting is the discovery of a new group of somewhat 
problematic organisms which have been grouped together under the generic 
name Rickettsia. Up to now their presence has been shown, more or less 
satisfactorily, to be associated with three types of human fevers, viz. typhus, 
trench fever and possibly Rocky Mountain spotted fever, and in the last few 
years a certain number of papers have appeared on this subject, the most 
comprehensive of which are those published by the British War Office Com¬ 
mittee and the American Commission on trench fever. In addition it has 
been suggested that many other human diseases are caused by these organisms, 
but the evidence is so very unsatisfactory that it may be disregarded. 
Up to the present the papers which have been published on Rickettsia are 
concerned mainly with experimental and clinical investigations. With the 
object, therefore, of attempting to throw some light on the nature of the 
organisms themselves, in spring, 1919, at the suggestion of Professor Nuttall, 
I took up the study of the Rickettsia bodies associated with trench fever. 
The investigation eventually resolved itself into three main divisions. 
First, the examination of a series of lice from persons known not to have been 
exposed to trench fever or typhus, in order to determine whether or not they 
contained Rickettsia ; secondly, observations on R. quintana obtained by 
feeding lice, known to be uninfected, on a patient suffering from trench fever; 
finally, the examination of a number of blood-sucking insects in order to see 
how widespread is the occurrence of infection with Rickettsia. 
(1) Examination of Uninfected Lice. 
One of the arguments which has been used against the view that Rickettsia 
are parasites is the statement that these bodies may be found in uninfected 
lice and are normal constituents of the alimentary canal. Thus Brumpt (1918), 
1 Read before the Kasr-El-Ainy Staff Club, School of Medicine, Cairo, on 13 Nov. 1920. 
2 The expenses of this investigation have been partly defrayed by the aid of a grant from the 
Medical Research Committee. 
