150 



EVENINGS AT THE MICROSCOPE. 



same general form, but constituting an imperfect tube ; a 

 tube, that is to say, from which about a third of the peri- 

 phery is cut away, so as to serve as a sheath for the 

 tongue, which ordinarily lies within its concavity. 



I scarcely know whether this 

 apparatus is not more wonderfully 

 delicate than any we have ex- 

 amined — even than that of the 

 Flea. And how effective it is 

 you doubtless well know ; for 

 when the array of lancets is 

 introduced into the flesh, you are 

 aware that a tumour is left, which, 

 by its smart, itching, and inflam- 

 mation, causes much distress, and 

 lasts many hours. This effect is 

 probably produced partly by the 

 deep penetration of the instru- 

 ments — for they are fully one- 

 sixth of an inch in length, and 

 they are inserted to their very 

 base — and partly by the injection 

 of a poisonous fluid, intended, as 

 has been conjecturally suggested, 

 to dilute the blood, and make it 

 more readily flow up the capil- 

 lary tubes. The channel through 

 which this fluid is injected is pro- 

 bably the tongue, which you see 

 to be permeated by a tube containing a fluid ; and the same 

 channel may afford ingress to the diluted blood. 



The labium does not enter the wound. If you have 

 ever had the philosophic patience to watch a gnat while 

 puncturing your hand, you have observed that the knob at 

 the end of the proboscis is applied to the skin, and that 

 then the organ bends with an angle more and more acute, 



LANCETS OF FEMALE GNAT. 



a, labium. d, tongue. 



&, &, mandibles. e, labrum. 

 c, c, maxillae. 



