142 



trates the open orifices of the trachse, evidently pro- 

 duces this kind of resurrection. 



The trachae, or air-vessels, are divided and sub-di- 

 vided in a prodigious degree. May they not resemble 

 'so many sieves, which, by separations suitably contrived, 

 are capable of furnishing to 1 each part an air of a more 

 or less subtle nature, as occasion requires ] There are 

 commonly reckoned to be nine stigmata on each side t>f 

 the body; but sometimes they ave more in number, at 

 others, fewer. The same insect has some that are of 

 greater or less 'importance to it, or whose functions are 

 more or less necessary. In several species, the principal 

 stigmata are placed behind ; i others, at the head : in- 

 stead of stigmata, they are pretty frequently observed 

 to have little tubes of different lengths. 



3. The circulation of the blood is performed in insects 

 with great regularity. We trace it Iry our sight : in some 

 species of loi'g and transparent worm>, we- may see the 

 heart, or principal artery, contract and dilate itself suc- 

 cessively in every part of its extent. H seems to be 

 composed of a great number of little hear-, placed end 

 to end, that transmit the blood to each other. 



We are yet ignorant in what manner the blood is con- 

 veyed into the grand aitery : its principal ramifications, 

 and the canals analogous to veins, a; e. equally unknown. 

 We are only certain, that in many species, for the most 

 part of the creeping sort, the principle of circulation is 

 towards the hinder part ; whereas, in others, it is to- 

 wards the head. It is very probable, that the grand 

 artery shoots forth from both sides of it, several branches 

 that are invisible, by reason of their extreme fineness or 

 transparency, and that distribute the b!<;od to every 

 part : other branches are, without doubt, connected w itk 

 them, and conduct the residue of the blood to the prin- 

 cipal trunk < f veins, which is imagined to be perceived, 

 on the opposite side of the Least. The blood of insects 

 is a subtle liquor, transparent, commonly without co'- 

 lour; and though it be not hi the least inflammable* 



