274 KATHARINE FOOT. 



posited. The parent lice were then discarded. Seventy-five per 

 cent, of the eggs hatched and forty of the nymphs were reserved 

 to raise to maturity. These fed normally and showed no tend- 

 ency whatever to attack each other, though twenty were fed in 

 one small tube. A normal number reached the mature stage and 

 the experiment was then closed. 



Results: The only abnormal feature in the life history of two 

 generations of lice was the marked tendency of the first genera- 

 tion to attack each other during the feeding hour. There is no 

 evidence that potassium iodid taken by the host is either in- 

 jurious or distasteful to the lice. 



The Reaction of Lice to the Blood of the Host Taking Sodium 



Salicylate. 



Host: Helen P., age 25 years. 



Sodium Salicylate: Prescription by Col. R. P. Strong, 15 grains 

 daily (5 grains 3 times a day). 



No. of Lice: Four males and four females. Collected from a 

 healthy woman at St. Louis Hospital, May 14, 1919. The lice 

 were fed one hour daily. After seven days feeding on the pre- 

 sumably medicated blood., the eggs were collected daily until 159 

 were deposited. The parent lice were then discarded. Eighty- 

 five per cent, of the eggs hatched and twenty of the nymphs were 

 reserved to raise to maturity. Sixteen of these survived and 

 after they reached the mature stage the experiment was closed. 



Results: Only one possibly abnormal feature has been observed 

 and the experiment must be repeated to determine whether it is 

 due to the sodium salicylate. More than seventy of the Fj. 

 generation were dissected for cytological study and a surpris- 

 ingly small per cent, were males. After dissecting about thirty 

 the following exact record was kept of the last thirty-nine dis- 

 sected. Of these thirty-nine two only were males. 



A Case of So-called Immunity to Attack from Lice. 



There seems to be trustworthy evidence that many people are 

 immune to attack from one or more species of insects that feed 

 on human blood. 



Nuttall ('17) gives the following data in relation to Pediculus 



