HUMAN PEDICULI 329 



must of course be made through the skin. But, in 

 consequence of its retractile character, there has been a 

 great deal of difficulty in determining the real structure 

 of the sucking apparatus, and it is necessary to carry 

 out careful observations on the living or recently killed 

 insects, before the details can be made out. The old 

 Dutch naturalist Swammerdam took great pains in 

 investigating the matter, and showed clearly that there 

 was a suctorial proboscis, which could be thrust out 

 from the head and entirely retracted again. But, as 

 he himself says, " this proboscis is, on account of its 

 diminutive size, not to be demonstrated except with 

 great painstaking, and it is perhaps nothing but a piece 

 of good luck if one succeeds in seeing it." This being 

 the case, it is perhaps not surprising that since Swam- 

 merdam 's time some authorities have denied the ex- 

 clusively suctorial character of the apparatus, and have 

 maintained that true biting organs are present, whence 

 they attributed the irritation produced by the insects on 

 their hosts to the effects of a real pinching bite. This, 

 however, was a mistake, arising from the fact that only 

 dead specimens were examined, and those, too, under 

 pressure, so that the apparatus could only be seen 

 through the skin as it lay contracted inside the head, 

 in consequence of which it was misinterpreted. About 

 twenty-five years ago Professor Schiodte, a Danish 

 naturalist, by careful observations on the living insect 

 (in this case P. vestimenti), confirmed Swammerdam's 

 statements, and determined with greater accuracy the 

 true nature of the proboscis. He obtained an abundant 

 supply of material from a workhouse (Danish), and 

 having enclosed some specimens in a glass tube for two 

 or three days without food, so that they might the more 

 readily fall to when released from confinement, he 



