142 RICKETTSIA PROWAZEKI IN LICE 



half-digested blood contents. Occasional passing confusion 

 may be caused by the presence of particles of spermatozoa 

 in every stage of development from the testes of male lice. 

 Another source of possible error in the examination of smears 

 of rickettsia is the introduction of organisms by the fluids, 

 such as stain or water used in the process of staining. 



In sections, the cytoplasm of swollen epithelial gut cells may 

 be granular and assume forms so like rickettsia that it is diffi- 

 cult to be certain that organisms are not present. The granu- 

 lar appearance of cells of the salivary glands and of Malpighian 

 tubules especially may be confusing. The free border of the 

 epithelial gut cells is covered with a cuticular layer. In sec- 

 tions it usually appears as a hyaline and structureless border. 

 Sometimes, especially at the anterior end of the mid gut, the 

 cuticular substance is disposed so as to produce a ciliated ap- 

 pearance. A tangential section of such an area may produce 

 an appearance somewhat resembling a collection of cocci. 

 Rickettsia pediculi are always on this border and fill its edgings 

 deep between the epithelial gut cells. 



