42 LOUSE FEEDING EXPERIMENTS 



As a rule the louse boxes were applied to the outer surface of 

 the leg. This region is easily manipulated and the skin is not 

 sensitive. The lice will not feed through the bolting cloth unless 

 the boxes are firmly applied to the skin and kept immobilized; 

 the death of the lice in a number of experimental boxes in our 

 early experiments was due to starvation through failure to 

 realize this. Another cause of the loss of lice was the placing 

 of boxes on patients whose skins were still greasy with the 

 mixture of oils used in delousing. The lice in one box were 

 killed by a few drops of alcohol accidentally dropped on it. 



In view of the possibility of infection by the feces from in- 

 fected lice, great care was taken to avoid scattering the dry 

 feces. Gloves were worn while applying the boxes and cloths 

 wet with a solution of bichloride of mercury were placed upon 

 a rubber sheet beneath the patient's leg in order to catch 

 the droppings. The box, when applied, was covered with an 

 ample pad of absorbent cotton and fixed in position by a 

 firmly applied bandage. At the end of the feeding, the bandage 

 was cut, the louse box returned to an individual receptacle 

 (glass Stender dish), the bandage and cotton placed in a paper 

 bag for burning, and the skin of the leg disinfected with al- 

 cohol. 



Between feedings, the louse boxes, each in a separate glass 

 dish, were kept in an incubator. The temperature of the in- 

 cubator is a very important factor. Early in our experiments, 

 when the incubator temperature was kept at 20-25C. positive 

 findings in the lice were rare, while toward the end of the ex- 

 periments, when the incubator was maintained in the neighbor- 

 hood of 30C. some of the lice in each box invariably were in- 

 fected with rickettsia. Other factors influencing favorably the 

 acquisition of rickettsia by lice were length of time allowed for 

 each feeding, extended to one hour, and the perfect immo- 

 bilization of the boxes; both were observed in our later experi- 

 ments. The usual period covered by the feeding of a box was 

 twelve to sixteen days, but occasionally it was extended to 

 twenty-four or more days up to twenty-nine. 



