CONTROL EXAMINATIONS OF STOCK LICE 



At the conclusion of the research control examinations were 

 again made. The results of these examinations are shown in the 

 following table (Table I); they are uniformly negative except 

 for Mr. Bacot's lice after the onset of his illness. Other evi- 

 dence of the cleanliness of our American stock lice was fur- 

 nished many times during the course of our work in the failure 



TABLE I. CONTROL EXAMINATIONS OF STOCK LICE 



Grand total 383 



* In this table, "RE" indicates extracellular rickettsia. Extracellular organisms, 

 indistinguishable from Rickettsia pediculi or Rickettsia quintana, were found in Mr. 

 Bacot's lice after he developed trench fever. 



Intercellular rickettsia were found in none of these 383 lice. 



to find micro-organisms in any louse of numerous boxes re- 

 moved from typhus patients when conditions favorable to the 

 development of Rickettsia prowazeki had not been maintained. 



3. CONTROL EXAMINATIONS OF POLISH LICE 



In order to ascertain if rickettsia occurred in lice found on 

 apparently normal persons, lice were collected on three oc- 

 casions from the garments of apparently healthy clients of a 

 public bath-house in Warsaw. In all' 148 lice were examined, 

 70 by serial sections, 78 by smears of the abdominal and 

 thoracic organs. Rickettsia were found in twelve, in eight by 

 smear preparations of the abdominal and thoracic organs, and 

 in four by serial sections. The rickettsia in the serial sections 

 were wholly extracellular. The rickettsia in the smear prepara- 



