APP.] CHEMICAL BASIS OF THE ANIMAL BODY. 721 



analysis would lead at once to the ranking of lardacein as a proteid, and 

 this is strongly supported by other facts. Strong hydrochloric acid 

 converts it into acid-albumin, and caustic alkalis into alkali-albumin. 

 On the other hand, it exhibits the following marked differences from other 

 proteids: It wholly resists the action of ordinary digestive fluids; it is 

 coloured red, not yellow, by iodine, and violet or pure blue by the joint 

 action of iodine and sulphuric acid. From these last reactions it has 

 derived one of its names, ' amyloid,' though this is evidently badly chosen ; 

 for not only does it differ from the starch group in composition, but by 

 no means can it be converted into sugar : this latter is one of the crucial 

 tests for a true member of the carbohydrate group. According to 

 Heschl 1 and Cornil 2 anilin-violet (methyl-anilin) colours lardaceous 

 tissue rosy red, but sound tissue blue. 



The colours mentioned above, as being produced by iodine and sulphuric acid, 

 are much clearer and brighter when the reagents are applied to the purified lardacein. 

 When the reagents are applied to the crude suhstance hi its normal position in the 

 tissues, the colours obtained are always dark and dirty-looking. 



Purified lardacein is readily soluble in moderately dilute ammonia, 

 and can, by evaporation, be obtained from this solution in the form of 

 tough, gelatinous flakes and lumps ; in this form it gives feeble reactions 

 only with iodine. If the excess of ammonia is expelled, the solution 

 becomes neutral, and is precipitated by dilute acids. 



Preparation. The gland or other tissue containing this body 

 is cut up into small pieces, and as much as possible of the surrounding 

 tissue removed. The pieces are then extracted several times with wator 

 and dilute alcohol, and if not thus rendered colourless, are repeatedly 

 boiled with alcohol containing hydrochloric acid. The residue after 

 this operation is digested at 40 C., with good artificial gastric juice in 

 excess. Everything except lardacein, and small quantities of muciii, 

 nuclein, keratin, together with some portion of the elastic tissue, will 

 thus be dissolved and removed 3 . From the latter impurities it may be 

 separated by decantation of the finely-powdered substance. 



The chief products of the decomposition of proteids are ammonia, car- 

 bonic anhydride, leucin and tyrosin. Several other bodies, for the most 

 part, like leucin, amidated acids, such as aspartic acid, gtutamic acid, 



1 Wien. med. Wochenschr. No. 32, S. 714. 



2 Compt. Rend. T. LXXX. (1875), p. 1288. 



3 RUhne und Eudneff, Virchow's Arch. Bd. xxxnr. (1865), S. 66. 



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