of the Corneous parts of Insects. 115 



Grs. Grs. 



Carbon 1*500 or per cent. 45-73 



Hydrogen 0187 5-70 



Nitrogen 0-313 9-54 



Oxygen 1-280 39.02 



3-280 99-99 



On heating the tube, to ascertain the quantity of water formed 

 in this experiment, (in which my friend J. F. Daniell, Esq. had 

 the goodness to co-operate) the first portions that came over ex- 

 haled a decided odour of prussic acid. 



The near accordance of the preceding results entitles me to 

 consider them as not very wide of the true composition of the sub- 

 itance in question. That they are absolutely accurate, in regard 

 to the proportions of the several elements, I will not venture to 

 assert, but I think there can be no question as to their quality^ nor 

 that nitrogen is essentially necessary to the composition of the 

 carapace of insects, and consequently that M. Odier's conclusion 

 that it rather belongs to the vegetable than the animal kingdom is 

 erroneous. 



I shall mention one more experiment. — An unweighed portion, 

 consisting of a mixture of the elytra of the Silpha obscura, a car- 

 nivorous insect, Geotrupes stercorarius, which feeds on dung, 

 and the Cetonia aurata, which feeds on vegetables, all perfectly 

 purified by potassa, so as not in the slightest degree to change the 

 colour of moistened turmeric paper exposed to the vapours in 

 distillation, were burnt with peroxide of copper, merely to ascer- 

 tain the quality of the gases produced. About 18 cubic inches 

 were collected, which, after the action of potassa, left 1-35 cubic 

 inch of nitrogen. 



The Prussic acid formed in the second experiment mentioned 

 above is an additional proof that nitrogen is an element in the com- 

 position of the carapace, being as our readers are aware a com- 

 pound of carbon, hydrogen, and nitrogen. 



J. G. C. 



