SUMMARY 129 



The rickettsia that concern us most are those in lice. The 

 early control work by Brumpt and Strong, apparently based 

 wholly upon the examination of smear preparations, showed 

 the presence of rickettsia in lice from presumably disease free 

 persons in France. Munk and da Rocha-Lima in 1917 showed 

 that there were two types of rickettsia in lice, one extracellular, 

 which multiplies wholly outside of the epithelial cells of the 

 gut in the lumen and upon or in the cuticular border of the 

 cells, and one associated with typhus which multiplies ex- 

 clusively within the epithelial cells of the louse's gut. The 

 former he named Rickettsia pediculi and he believed it to be 

 a non-pathogenic micro-organism confined to the louse. The 

 latter is Rickettsia prowazeki. In no control work has it been 

 shown that intracellular rickettsia occur in lice from a cer- 

 tainly typhus free population, although both da Rocha-Lima 

 and Toepfer state that very rarely Rickettsia pediculi may 

 invade the cells. We, in view of the heavy typhus infestation 

 of the countries in which this work was done, and our failure to 

 find intracellular rickettsia in the controlled British stock lice 

 fed upon Mr. Bacot during his illness with trench fever, regard 

 these observations as open to strong doubt. Twenty-six lice 

 of the British stock fed upon Mr. Bacot during his illness were 

 studied in sections. Seventeen contained extracellular rickett- 

 sia. Nine were negative. In none did we find intracellular 

 rickettsia. On the other hand, since the association of rickett- 

 sia with trench fever has been given etiological significance by 

 Toepfer (1916), Munk and da Rocha-Lima (1917), Arkwright 

 and Bacot (1919), Byam (1919), and since the rickettsia ob- 

 served by these authors are of the extracellular proliferating 

 type and indistinguishable from Rickettsia pediculi of da 

 Rocha-Lima, the question of deciding the specificity of rickett- 

 sia for trench fever is a most difficult one. The query is: are 

 Rickettsia quintana (wolhynica) and Rickettsia pediculi identical? 

 If so, is this rickettsia the cause of trench fever? 



