317 



Such is found to be the case, in some respects, in the vegetable kingdom, 

 and since vegetable structure has been found in the niollusk alluded to, 

 it may be presumed to be present in the higher forms of life, as in the 

 vertebrates, including man ; and as nature does nothing in vain, the 

 presence of cellulose in animals would imply that it has some function 

 to perform for which it is peculiarly adapted in th^ir vital economy. 



That the consideration of animal and vegetable pathology comes 

 strictly within the scope of agricultural investigation, is demonstrated 

 by the ravages of the* rinderpest, horse-iniiuenza, and numerous vege- 

 table-blights, the cause or causes of which have so frequently eluded the 



of potash, which removes adhering albuminous substances, and has no action upon 

 chitine ; again washing with distilled water, and purifying the residue with alcohol 

 and ether. 



"When chitine (from the carapace of the crab) is boiled for several hours with dihite 

 sulphuric acid, only the softer membranes are attacked, while the more solid integu- 

 ments become loose and soft, and form, after pressing and waAiug with water, a mass 

 having almost the consistence of stai'ch. The acid liquid supersaturated witli lime, 

 and then neutralized with sulphuric acid, yields neither tyrosine nor leucin6, but con- 

 tains ammonia, together with amorphose sugar, inasmuch as it precipitates cuprous 

 oxide abundantly from an alkaline solution of cupric oxide. (Stiideler.) Berthollet 

 (Ann. Ch. Phys. [3] Ivi, 149,) likewise obtained sugar from chitine, (prepared from the 

 integuments of lobsters, crabs, and cantharides,) by macerating it in strong sulphuric 

 acid till it was dissolved, dropping the solution into one hundred times its volume of 

 boiling water, boiling for an hour, saturating with chalk, &c. 



Tlie above-mentioned pasty residue is colored brown-red by iodine, like unaltered 

 chitine ; and by prolonged boiKng with sulphuric acid, yields an additional quantity of 

 sugar, while the undissolved portion always contains nitrogen. The same substance, 

 after removal of the acid, forms with water a turbid emulsion, which takes a long 

 time to clarify, and dries up by spontaneous evaporation to a soft, skin-like membrane, 

 which exhibits, with iodine-water, the same reactions as the original chitine. (Stiid- 

 eler..) 



The composition of chitine is determined by the following analyses : 



"^ni'anai^ses" I^^— • Schlossberger. Stadeler. Ca^c^laUon. 



Carbon 46.64 46.73 46.64 46.32 46.35 



Hydrogen 6.60 6.59 6.60 6.65 6.44 



Nitrogen 6.56 6.49 6.56 6.14 6.01 



Oxygen 40.20 40.19 40.20 40.89 41.20 



Fr^my found in chitine 43.35 carbon. 6.65 hydrogen, and no nitrogen; whence he re- 

 gards chitine as isomeric with cellulose, (44.4 C, 6.2 H, and 49.4 O.) Gerhardt regarded 

 Fr^my's results as more correct than those of the German chemists, because chitine 

 yields by dry distillation only acetic acid and empyreumatic oil, withont any ammonia, 

 and the i)rodnct8 of its putrefaction under water are different from those of most nitro- 

 genous substances. But the analyses above given exhibit a closeness of agreement 

 which could scarcely be expected if the substances operated upon had been impure. 



Stadeler regards chitine as a glucoside, C^Hi^NO^, which is resolved by boiling with 

 acids into glucose and lactamide, (or alanine or sarcosine :) 



C^H'SNO" -f 2H=0 = C^H'^Os -f C^H^NO^. 



If this decomposition really takes place, lactic acid should likewise be obtained as a 

 product of the trausformation of the lactamide or alanine ; but the presence of lactic 

 acid among the products has not yet been demonstrated. Stadeler also suggests that 

 chitine (at least in Crustacea) may be formed by the union of lactate of ammonium with 

 gum, and elimination of water : 



[C-^H^O^H,NH^ -f C^HioO^ = CsH'sNO^ -f 2H20,] 

 Acid lactate of Gum. Chitine. 



ammonium. 



Inasmuch as he has found gum in the juices of crabs and other Crustacea, the 

 presence of lactic acid in the gastric juice of the lower animals is by no means improb- 

 able. 



