8 TECHNIC 



tions were also indistinguishable from those associated, with 

 trench fever. (Repeated examination accounts for the slight 

 difference between the figures given here and those mentioned 

 in a preceding communication (Preliminary Report from the 

 Typhus Research Commission of the League of Red Cross 

 Societies to Poland, Wolbach, Todd, and Palfrey, 1920). 



Since Mr. Bacot's illness developed fourteen days after work- 

 ing with these lice, we believe that his infection was probably 

 contracted from them. His further observations (Bacot, 1921) 

 prove that a person in good health may infect lice with rick- 

 ettsia for at least three months after the cessation of febrile 

 attacks or other obvious symptoms of trench fever. 



4. THE FEEDING OF LICE 



The normal louse stocks and the lice fed upon patients 

 were kept in cages (Fig. 1) substantially of the type de- 

 scribed by Nuttall (1917, p. 106). A metal, not cardboard, 

 box was used; the lower margin was flanged to facilitate the 

 stretching and fastening of fabric. This flange at first was 

 made by soldering a wire around the lower margin, but the spun 

 flange is preferable, as it permits of rapid sterilization in the 

 free flame. Bolting or milling cloth (to be obtained from dealers 

 in millers' supplies) was used in place of chiffon as recom- 

 mended by Nuttall. Bolting cloth is made of silk and is very 

 strong and durable. We used cloth with 70 apertures to the 

 inch; these are small enough to prevent the escape of larvae 

 and large enough to permit all stages of the lice to feed freely. 

 Narrow strips of adhesive plaster were used for fastening the 

 bolting cloth to the bottom of the box. In wearing boxes 

 containing the stock lice the straps devised by Nuttall proved 

 useful (Figs. 2 and 3). To boxes designed for continuous wear 

 we added a raised metal strap across the aperture in the 

 cover under which the strap could be passed, thus remov- 

 ing any possibility of losing the box (Figs. 1, 2, and 3). In 

 making up a cage for lice the border of the aperture in the 

 bottom of the box should be pushed out slightly so that it 

 presses against the bolting cloth which is drawn tightly over it. 



