of the Corneous parts of Insects. 105 



Albumen is distributed through almost all the animal organs, 

 therefore it is not surprising that it should be found in the homy 

 parts of insects ; it exists in them, perhaps, only as the principle 

 of the nourishing juice impregnating those organs. 



I have not particularly examined the extractive matter soluble 

 in water, nor the other brown substance soluble in potassa and 

 insoluble in alcohol, which I have mentioned above. M. Lassaigne, 

 who has made some experiments on elytra, informs me that he has 

 found the latter substance to be analogous to the animal matter 

 met with in the cochineal. This substance, which exists in consi- 

 derable quantity, seems to form the base of the colour of the horny 

 pieces, for the brilliant colours which serve as distinctive charac- 

 ters, are almost always merely superficial on the elytra. These 

 two bodies require to be more particularly studied, in order 

 thoroughly to understand their nature. 



Of the substance having the appearance of horn. 



I have said that this substance is obtained by treating the elytra 

 with a hot solution of potassa, and that it is consequently insoluble 

 in that re-agent, which merely deprives it of the other animal 

 matter with which it is associated. 



This character at once distinguishes this body from many others, 

 as horn, hair, and epidermis, which, according to M. Vauquelin, are 

 nearly of the same nature and are all soluble in potassa. Like 

 them Chitine* the name I have given this substance from the 

 Greek % /Lv (a covering), is soluble in sulphuric acid with the 

 assistance of heat. But nitric acid affords a distinguishing charac- 

 ter of it : it is known that horn, hair, and epidermis become yel- 

 low in this acid, in consequence of the formation of a certain 

 quantity of the bitter matter of Welther ; Chitine does not become 

 yellow by the action of nitric acid, but is dissolved when digested 

 in it with heat. 



limbs, and tail. The shell of the tortoise is called its carapace. (See Diet, 

 des Sciences Naturelles. Art. carapace.) C. 



* Every man has a right to name his own child, but we think M. Od.er 

 might have made a happier election. Elytrinc would have been more significant 

 and at least as euphonious. Ed. 



