NOTES ON PEDICULUS VESTIMENTI. 

 RECORD SHOWING THE PROPORTION OF MALES TO FEMALES. 



275 



vestimenti. He says Hase ('15) studied the effect of lice on 

 behalf of the war office in Germany. He questioned one thou- 

 sand persons on the subject and was able to place them under 

 four groups. First, persons who are not attacked by lice; sec- 

 ond, those who are attacked continuously and are sensitive to 

 bites ; third, those who are suffering from bites became immune 

 to the effects ; fourth, those who have been bitten continuously, 

 but do not suffer from the effects. In group No. I, he mentions 

 a man who remained untouched by lice, but suffered from fleas. 

 In group No. 2, a man who suffered from both lice and fleas. 

 In group No. 3, a man w r ho was bitten by lice but avoided by 

 fleas. 



It is frequently stated by people whose intelligence and ac- 

 curacy of statement are beyond question that they are never 

 attacked by a definite species of insect though surrounded by 

 people who are infested by them. If such evidence is an ac- 

 curate statement of facts, such facts merit careful scientific ex- 

 periment not only to demonstrate their accuracy, but to search 

 for the cause of the immunity. In the case of Pediculus vesti- 

 menti the practical value of such investigations is self-evident. 



In June, 1919, I met in Soissons a very intelligent soldier who 

 is convinced that Pediculus vestimenti will not attack him. Ser- 

 geant Du R., of Ohio, age 28, has been in France two years, was 

 many months at the front and frequently exposed to the pest. 

 He slept with his brother from February 15 to May 5, 1917, and 

 during that time his brother was infested with Pediculus vesti- 



