OP THE INVERTEBRATE ANIMALS. 17 



its alkaline solution by acids, is insoluble in water, alcohol and 

 Eether, amorphous, and of a resinous aspect ; it requires separate 

 examination, which would be especially interesting in regard to 

 the possibility of its metamorphosis into the other colouring 

 matters of beetles. As regards the true chitine, i. e. the colour- 

 less transparent residue of the elytra which is insoluble in water, 

 alcohol, aether and potash, the sharp outline of its histological 

 elements, and especially the perfect preservation of the hair-cells, 

 which can easily be confirmed by admeasurement, are in favour 

 of this substance being a compound of carbon, hydrogen, ni- 

 trogen and oxygen. This chitine is soluble without change of 

 colour in concentrated muriatic or nitric acid, and may be kept 

 boiling for some days in the strongest solution of potash without 

 undergoing any change. When heated with water to 536° F. in 

 hermetically sealed metallic tubes, it becomes brown and brittle ; 

 the water, however, does not contain a trace in solution, and 

 the minute structure when magnified appears unchanged. Strong 

 solution of potash with increase of the heat to 410° F. in strong 

 glass tubes yields the same result ; water at lower temperatures of 

 course exerts as little action. When immersed in concentrated 

 sulphuric acid it swells and dissolves without any change of co- 

 lour; the solution gradually becomes coloured, and in twenty-four 

 hours w-e obtain a fluid which is coloured black by a slight but 

 extremely fine powder in a state of suspension, is of a pungent 

 odour, and ammonia can be detected in it by excess of potash or 

 chloride of platinum, whilst the fluid obtained on distillation, 

 when treated with sulphuric acid and alcohol, evolves acetic 

 aether ; peroxide of mercury is dissolved in it without reduction 

 forming a persalt of mercury, and it has the odour of acetic 

 acid ; in fact, it contains a considerable quantity of this acid. It 

 does not, however, evolve any sulphurous acid ; neither does it 

 contain any formic acid, as is evident from its action upon peroxide 

 of mercury ; nor could the formation of the latter be detected 

 even after exposure to the air for fourteen days. Submitted to 

 destructive distillation, water, acetic acid and acetate of ammonia 

 pass over, and lastly an empyreumatic oil, but in comparatively 

 small quantity ; the remaining cinder so accurately preserves the 

 form of the elytra, that we can obtain the entire beetles reduced 

 to a cinder either in the walking, running or flying attitude, and 

 without the least structural alteration, by drying and properly 

 laying out the colourless and transparent chitine skeletons ob- 



VOL. V, PART XVII. C 



