^04 Microscopical Essays. 



The probofcis of the gnatconfifts of a great number of ex- 

 tremely delicate pieces, all concurring to one purpofe ; this is 

 the inftrument with which it ftrikes the flefli, and fucks the blood 

 of animal bodies. The only part exhibited to the naked eye is the 

 f heath, which contains all the other pieces. The flieath is a cy- 

 lindric tube, which is flit in fuch a manner, that the infe6t can 

 feparate it from the dart, and bend it more or lefs in proportion 

 as the dart is plunged into the wound; From this tube the 

 fling is darted, which confifts of five or fix blades or lancets, 

 lying one over the other ; fome of thefe are fliarpened like a two- 

 edged fword, while others are barbed, and have a vaft number of 

 cutting teeth. When this bundle of blades is introduced into a 

 vein, the blood rifes up the blades as fo many capillary tubes. 

 The moment the gnat lances it's dart into the flefh, two or three 

 drops of a fluid are infmuated by it into the wound. It is this 

 fluid which is fuppofed to caufe thofe infupportable itchings that 

 we feel when flung by this little creature. 



Plate XVI. Fig. t B is the probofcis, or that apparatus of a 

 tabanus with which it pierces the flan of horfes and oxen, and 

 nouriflies itfelf with their blood, The Angular and compound 

 flxu&ure, together with the admirable form andrexquifite beauty 

 of this apparatus, difcovers fuch a view of the wifdom, power* 

 and greatnefs of it's infinite compofer, as mull flrike with admi- 

 ration every contemplative obferver, and lead him to reflect on 

 the weaknefs, impotence, and nothingnefs of all human mecha- 

 nifm, when compared with the immenfe ftdll and inimitable 

 finifliing difplayed in the fubjecl; before us. The whole of this 

 formidable apparatus is compofed of fix parts, (exclufive of the 

 two guards, or feelers, a a,) all of which are inclofed in a flefhy 



cafe 5 



