DESCRIPTION OF PLATES 213 



PLATE IV 



FIGURE 18. Louse Box 58, Louse 14. Rickettsia prowazeki. 



1,200 diameters. Smear preparation of the gut of a louse. This draw- 

 ing illustrates rickettsia free and contained within epithelial cells. They 

 occur as granules singly or in pairs. Among the paired forms are some 

 of larger size. 



FIGURE 19. Bed-bug caught in Warsaw. Rickettsia lectularius. 



1,800 diameters. Smear showing a burst Malpighian tubule. Very 

 numerous rickettsia, varying in morphology from single granules to 

 short paired rods. 



PLATE V 



FIGURE 20. Mr. Bacot's stock, Louse 2. Rickettsia pediculi. 



2,000 diameters. Section. Characteristic granules, disposed singly or 

 in pairs, occurring free in the lumen and, especially, closely placed along 

 the cuticular border of the epithelial cells of the gut. (Compare with 

 Figure 32, plate IX, which is from a different field.) 



FIGURE 21. Louse Box 58, Louse 14. Rickettsia prowazeki. 



2,000 diameters. Smear. Epithelial gut cells from an experimental 

 louse are shown. They are closely packed with finely granular rickettsia 

 bodies. (Compare with Figure 18, plate IV.) 



PLATE VI 



FIGURE 22. Louse Box 48, Louse 10. Rickettsia prowazeki. 



2,000 diameters. Smear. The epithelial cells of the mid-gut have been 

 squashed in making this preparation; their contents are spread over 

 the slide. Many rickettsia, as single or paired granules or as short single 

 or paired rods, are scattered about the field. A tangled mass of chain- 

 like rickettsia "threads" fills a large part of the field. (Compare with 

 Figure 13, plate III.) 



FIGURE 23. Louse Box 54, Louse 2. Rickettsia prowazeki. 



2,000 diameters. Section. This epithelial gut cell is closely packed 

 with rickettsia bodies. At one end of the cell the organisms are present 

 in a granular form; at the other end of the cell they appear as rods 

 which lie more or less regularly ordered in skeins. Among the finely 

 granular organisms lie others, singly or in pairs, which are considerably 

 larger and stain more deeply. (Compare with Figure 29, plate IX.) 



