66 INTERNAL ORGANS. 



already been said, but spreads about through the 

 interior of the body, taking the form of an irregular 

 mass of soft pulpy fat, greenish or whitish in colour, 

 which surrounds the organs of digestion, and fills up 

 every vacant place in the body, particularly in cater- 

 pillars, of which it forms a very large proportion of 

 the whole bulk. 



The more fluid portions appear to be taken up 

 through the membranes of the several organs, pro- 

 bably in a similar way to that by which they pre- 

 viously passed through the membranes of the small 

 intestine. On this subject, however, we are still very 

 much in the dark: though it is certain the fat is em- 

 ployed for the purposes of nutrition ; for it is always 

 stored up in great quantity before an insect passes 

 into the state of chrysalis, when it ceases to eat, and 

 often remains torpid for many months ; and is also 

 found similarly stored up in the female before the 

 eggs are laid, but after this disappears. 



The nutritive matter, whether it be fat or fluid, not 

 being carried through the body in arteries and veins 

 as the blood is in other animals, to nourish the several 

 parts, lies around and upon the parts to be nourished, 

 which absorb the peculiar portions they require, re- 

 jecting the rest ; and this may be required by other 

 parts for a different purpose. 



The more solid portions may be required by the 

 muscles, the layers of the intestines, the horny skin, 

 and perhaps by the nerves; while the more fluid por- 

 tion may be taken up by the gastric vessels, the bile 

 vessels, and the peculiar vessel, which is the only 

 organ found in insects in the least resembling a heart. 



ORGANS OF CIRCULATION. 



THE organ or vessel in question was called a heart 

 by Malpighi and Swammerdam, and the older natu- 

 ralists ; but though it is now commonly called the 



