DESCRIPTION OF PLATES 211 



FIGURE 4. Polish control Louse 27. Rickettsia pediculi? 



2,000 diameters. The rickettsia bodies illustrated were found (refer to 

 discussion of Polish controls in text, page 130) in lice taken from ap- 

 parently healthy inhabitants of Warsaw. The organisms occur as 

 granules, singly or in pairs, and as short rods, singly or in pairs. 



FIGURE 5. Bed-bug 2, Slide 1, Mr. Bacot's stock. Rickettsia lectularius. 

 2,000 diameters. This preparation is the extremity of a Malpighian 

 tubule dissected from one of the stock of bed-bugs brought from Eng- 

 land and maintained by Mr. Bacot. At one edge of the field lie cells 

 of the extremity of the Malpighian tubule. They are closely packed 

 v with rickettsia bodies. Free in the field are many other organisms. 

 The granules and short rods are disposed singly or in pairs. 



FIGURE 6. Dermacentroxenus rickettsi. 



2,000 diameters. From a smear preparation of an experimentally in- 

 fected tick (Dermacentor venustus) twelve days after feeding on an in- 

 fected guinea-pig. Tick LXVIII (Wolbach, 1919, p. 102). 



PLATE II 



FIGURES 7a, 7b, and 7c. 



3,600 diameters. These three drawings illustrate rickettsia forms in a 

 smear from the gut and gut contents of an experimental louse (Louse 10, 

 Box 48). Some of the swollen threads, as Ic, shown are probably 

 rickettsia forms. Nothing is stated concerning the nature of the re- 

 maining structures. 



FIGURE 8. Louse Box 50, Louse 2. Rickettsia prowazeki. 



2,400 diameters. Smear. The louse from which this smear of gut and 

 gut contents was made came from a box of lice in which infection both 

 by Rickettsia prowazeki and Rickettsia pediculi occurred. Thread-like 

 chains of Rickettsia prowazeki, similar to those illustrated here, are not 

 rare. In this drawing the unbroken outline of the bluish ground sub- 

 stance of the thread is indicated. Formed, apparently, within the sub- 

 stance of the thread are the purple granules indicating the poles of 

 rickettsia bodies of varying morphology. 



FIGURE 9. Louse Box 48, Louse 10. Rickettsia prowazeki. 



2,400 diameters. Smear. There are very many rickettsia bodies of 

 characteristic appearance in this smear of gut and gut contents; as 

 is illustrated, they often clearly show purple staining poles and a mid- 

 piece colored pale pinkish blue. In addition to these, threads of great 

 length are present. 



