102 Odior on the Chemical composiliun 



M. Robiquet's labours on Caiitharidcs luiviiig been directed to 

 the entire insect, and undertaken with particular views, very dif- 

 ferent from mine, have furnished me with only a few insulated 

 facts. I must, therefore, claim the indulgence of scientific men, 

 in proportion to the novelty of the subject I am entering on, and 

 in the study of which I have only my own judgment to trust to. 



The horny parts of insects consist of an assemblage of pieces 

 which form the covering of their bodies, and of some of their in- 

 ternal parts. As they all appear to me to be of the same nature, I 

 have chosen the elytra for the basis of my analysis, as being the 

 most insulated pieces, and consequently the most free from foreign 

 substances, and have afterwards compared the other parts with 

 them. 



I proceed to the examination of those organs in the order in 

 which I submitted tliem to experiment. 



The Cockchaffer (Uanneton — Scarabaeus melolontha, Lin.) 

 being the commonest insect at the season when I began my opera- 

 tions, I made the elytra of that animal the subject of my researches. 



I first submitted them to the action of water. One gramme 

 (15,444 Grs.) of the Cockchaffer's elytra, well cleaned, was in- 

 fused in cold water, for tw clve hours. When decanted, the water 

 was slightly tinged of a yellow colour and had become rather 

 less fluid. 



To ascertain the substances dissolved in this liquid, I evapo- 

 rated the solution to dr)uess with a gentle heat. As the liquid 

 bt'came warm some greenish brown filaments formed in it, indi- 

 cating the presence of a small quantity of albumen. The same 

 elytra being treated repeatedly with water, the infusions were 

 mixed together and afforded by evaporation 004 of a gramme 

 (0,6176 Gr.) of a substance composed of extractive matter, and a 

 little coagulated albumen. The residuum acted on by water re- 

 stored the blue colour of litmus paper which had been reddened 

 by an acid. To discover the nature of the alkali, the extract was 

 calcined in a plafina capsule ; the small quantity of ashes, thus 

 obtained, dissolved with effervescence in an acid, and the solu- 

 tion gave a yellow precipitate with muriate of platina. Hence the 

 alcali was carbonate of potassa. 



