HUMAN PEDICULI 333 



united into a tube from within which the second pair of 

 setae is protruded, similarly united, and terminating in four 

 small lobes, which seem to act as feelers. All this mechan- 

 ism can be thrust out to varying distances, and hence the 

 length of the exserted proboscis can be accommodated to 

 the thickness of the skin of the victim in the particular 

 place in which the animal is feeding ; by this means the 

 capillaries of the host are at length reached, when blood 

 will at once ascend the proboscis, the flow being accele- 

 rated and continued by the vigorous action of the pump- 

 like cavity in the digestive tube already mentioned. 



But to return to our decapitated head. The observer, 

 wishing to examine the structure of the proboscis under 

 a higher power of the microscope, put it under pressure 

 for that purpose, when instantly the whole apparatus 

 shot back into the head^ : and no further observations 

 could be conducted ; in this position the two sides of a 

 chitinous band, marked a in the diagram, look something 

 like biting jaws, and had been mistaken for such by those 

 who had not seen the protruded instrument. These appear 

 as a dark band across the under surface of the head in 

 Fig. no, which was drawn from a specimen prepared for 

 the microscope, and therefore more transparent than 

 usual, and beneath them the outlines of the retracted pro- 

 boscis can be traced. Schiodte had to carry out many other 

 observations on specimens prepared in a variety of ways 

 before the whole of the details enumerated above could 

 be determined; and whoever wishes to verify these results, 

 must be prepared to exercise great patience in the in- 

 vestigation. Leeuwenhoek was so much struck with the 

 beauty and delicacy of this feeding apparatus, even so far 

 as it was known in his time, that he appeals to its com- 

 plex character as evidence that a creature which possesses 

 so elaborate a sucking pump could not have been, as was 



