NOTES ON PEDICULUS VESTIMENTI. 263 



or killed one another but it prevented their feeding normally. 

 When fed only one hour during the twenty-four, they (as a rule) 

 feed the entire hour or stop only for short intervals they pass 

 each other and walk over each other without showing any mutual 

 antagonism. The process was quite reversed in the case of the 

 old sailor, for frequently, after feeding only five minutes, the 

 fighting commenced and continued the entire hour. This phe- 

 nomenon afforded not a little amusement in the laboratory and 

 was unhesitatingly attributed to the sailor's blood, for to avoid 

 the possibility of its being due to any foreign substance on the 

 skin, the arm was always carefully cleansed over the area used 

 for feeding. 



In order to secure peaceful feeding it was necessary to place a 

 single louse in each of the glass rings in which they were con- 

 fined while being fed. 1 The above described curious effect of the 

 abnormal blood of the host was not limited to the feeding hour, 

 for the lice frequently attacked one another in the cages in which 

 they were confined. Further, I found it exceedingly difficult to 

 raise the young lice they sometimes refused to bite at all and 

 often died two or three days after feeding. 



Being finally convinced that the blood of the old sailor was a 



1 In the above mentioned note on the spermatogenesis these rings and the 

 cages are described as follows : " When feeding the lice I at first used the usual 

 method of putting a number in a tube, inverting the tube on the arm and 

 holding it securely in place to prevent the lice from escaping. I found this 

 method unsatisfactory for several reasons and devised therefore quite a dif- 

 ferent technique : Lice cannot crawl up a glass surface if it is clean and 

 are therefore perfectly safe in a glass ring even if it is only 2 cm. high. I 

 had such rings made to order and fastened them securely onto the arm with 

 melted paraffine (photo). In this manner several different experiments can 

 be conducted at the same time and the generations can be kept separate 

 further the lice can be conveniently studied with a lens during the hour they 

 are feeding. For the remaining twenty-four hours they were kept in a 

 Pasteur incubator at a temperature between 27 and 29 C. While in the 

 incubator the lice were kept in cages such as those used in the laboratory for 

 raising various insects. This cage is the tube de Borel, in which is placed 

 an inner tube for the insects, this being held in the center by absorbent cotton 

 which is kept wet to insure sufficient moisture. I found the use of absorbent 

 cotton very inconvenient and replaced it with a short tube having an aperture 

 at both ends with a lip at each end sufficiently wide to center it in the tube 

 de Borel. The inner tube in which the insects are kept is dropped into this 

 shorter tube and an inch of water kept in the tube de Borel." 



