1911.] Parasitic in Pediculus vestimenti. 



513 



there is no evidence to show that there is any connection with the life-cycle 

 of any other organism. 



Contamination of experimental P. vestimenti by feeding on other vertebrates 

 has been rigorously excluded, so that no fallacious results can accrue from 

 outside sources. 



From the foregoing considerations, the conclusion obviously must be that 

 if H. pediculi be a stage in the life-history of a vertebrate trypanosome, the 

 said trypanosome should most probably be present in my blood, and should 

 have revealed itself by now. Eepeated cultures, thick-film blood examina- 

 tions, and ordinary smears, examined continuously during this research, have 

 all proved negative. Hence, all the evidence available points to the fact that 

 H. pediculi is a parasite of the insect Pediculus vestimenti, and has no 

 connection with any trypanosome of persons on whom lice may feed. Were 

 such a trypanosome to exist, it is surprising that it has not been recorded ere 

 this, considering the number of blood examinations undertaken in various 

 scientific institutions. 



Further, I do not think that H. pediculi has any connection with Leishmania, 

 as no symptoms of leishmaniasis have developed in me, and England is a 

 country free from the disease. However, the possible occurrence of such a 

 natural Herpetomonas in lice must be remembered in experimenting with 

 Pediculi as possible transmitters of Leishmania. 



" Wild " lice — the term commonly used to denote lice that were not bred 

 for purposes of investigation but collected at random — obtained from several 

 widely different districts in England, have also yielded the flagellates when 

 dissected. Doubtless, were more lice available from other areas, some also 

 would be infected. The inference is then, I think, fairly justified that 

 IT. pediculi occurs in a few body lice throughout England. 



Some Continental authorities would perhaps place H. pedictdi in the genus 

 Leptomonas. However, I have followed most English workers in considering 

 that members of the genus Herpetomonas are really uniflagellate, as originally 

 defined. 



Note on the Biology and Life-History of Pediculus vestimenti. 

 The study of parasitic Protozoa demands a good knowledge of the life- 

 history and habits of the host. In dealing with lice, great difficulty was 

 at first experienced, as the literature on the subject is very scattered and 

 unsatisfactory. Since the commencement of this research, a valuable 

 paper by Warburton (1909) has appeared, which gives details as to the 

 length of life of the lice, time of incubation, and rearing of the larvae. I 

 can fully confirm all that Warburton has recorded. 



