OF THE INVERTEBRATE ANIMALS. 15 



investigation upon the elytrum and horny tegument of the Cock- 

 chafer, Avhich in correctness of observation and modesty of style 

 excels many of those of his followers, forms an exception. He 

 first found that the parts we have mentioned, after treatment 

 with water, alcohol and potash, left a colourless transparent sub- 

 stance retaining the original form, which, being characterized by 

 the essential reactions of woody fibre, was considered by him, 

 in consequence of a readily explicable mistake, as free from ni- 

 trogen, and which as a peculiar modification of it, he desig- 

 nated by the name of Chitine. 



In 1843 Lassaigne* renewed the investigation ; he asserted 

 that he had detected this substance in the skin of the silk-worm 

 and spider, and having repeated merely the same reactions he 

 drew up such a magniloquent account as to render it almost 

 doubtful whether he or Odier was the discoverer ; and called it 

 Entomoderm, as the former name did not appear to him suffi- 

 ciently suitable. He however found nitrogen in it. 



It is clear that so long as we are unacquainted with the ele- 

 mentary composition and the true chemical relations of this sub- 

 stance, we know nothing about it ; and also that we cannot have 

 the shghtest idea of its physiological import, nor of the method 

 of its formation from those animal and vegetable substances, &c. 

 with which we are acquainted, much less ought we to assert 

 anything of the kind. This defect, which we could not attri- 

 bute to Odier in 1821, renders Lassaigne's statements at pre- 

 sent useless. 



Not long since Payen f resumed this subject in a notice ; he 

 estimated the amount of nitrogen in this substance in compa- 

 rison with the cellular membrane of plants ; it was 8*935 per cent, 

 in the shell of the craw-fish, and 9*05 in the silk-worm. 



Lastly, there is an analysis by Children and Daniell J, which 

 like Payen's is also incorrect ; they obtained, — 



Carbon 46-08 



Hydrogen .... 5*96 

 Nitrogen .... 10*29 



I found Odier's statements almost entirely correct. The elytra 

 consist of the true wing-plates and the muscles by which they 

 are moved ; the vessels of the latter of course contain blood, 



* Comjjtes Rendus, torn. xvi. p. 1087. 

 t Comples Rendus, torn. xvii. p. 227. 

 t Todd, Cyclopaedia of Anatomy and Physiology, vol. ii. p. 882. 



