AMYLUM MARANTiE. 031 



lie be cautiously heated on the object-stage of the microscope, the 

 tumefaction of the granules will be found to begin exactly at 70*" C. 

 Heated to 100' C. with 20 parts of distilled water, arrowroot yields a 

 seniitranspai'ent jelly of somewhat earthy taste and smell. By hydro- 

 chloric acid of sp. gr. 1"0G, arrowroot is but imperfectly dissolved at 

 40° C. 



The specific gravity of all varieties of starch is affected by the water 

 which they retain at the ordinary temperature of the air. Arrowroot 

 after prolonged exposure to an atmosphere of average moisture, and 

 then kept at 100' C. till its weight was constant, was found to have lost 

 13'3 per cent, of water. On subsequent exposure to the air, it regained 

 its former proportion of water. 



Weighed in any liquid which is entirely devoid of action on stai'ch, 

 as petroleum or benzol, the sp. gr. of arrowroot wa>s found by one of us 

 to be 1.504; but loGo when the powder had been previously dried at 

 100° C. 



Microscopic Structure of Arrowroot and of Starch in general. 

 — The granules are built up of layers, — a structure which may be 

 rendered evident by the gradual action of chloride of calcium, chromic 

 acid, or an ammoniacal solution of cupric oxide. When one of these 

 liquids in a proper state of dilution is made to act upon starch, or 

 when for that purpose a liquid is chosen which does not act upon it 

 energetically, such as diastase, bile, pepsin, or saliva, it is easy to obtain 

 a residue, which according to Nageli, is no longer capable of swelling 

 up in boiling water, nor is immetliately turned blue by iodine, except on 

 the addition of sulphuric acid ; but which is dissolved by ammoniacal 

 cupric oxide. These are the essential properties of cellulose ; and this 

 residue has been regarded as such by I^ageli, while the dissolved portion 

 has been distinguished as Granidose (Maschke, 1852). 



C. Nageli in his important monograph on starch ^ has described the 

 action of saliva when digested with starch for a day, at a temperature 

 of 40° to 47° C; he says that the residue is a skeleton, corresponding 

 in form to the original grain but somewhat smaller, light, and very 

 mobile in water. He concludes that its interstitial spaces nuist have 

 been previously tilled with granulose. 



This experiment, which has been repeated by one of us (F.), does not 

 in our opinion warrant all the inferences that Nageli has dra\\Ti from 

 it : it is true that many separate parts of the grain are dissolved by the 

 saliva, while others have disappeared down to a mere film, and others 

 again have been attacked in a very irregular manner. But we cannot 

 agree with the statement that anything comparable to a skeleton of the 

 grain has been left. After longer action at a higher temperature, which 

 however must not exceed Go"" C, a more copious dissolution of the 

 starch, either by saliva or by bile, takes place ; but in no case is it 

 complete.- 



Chemistry of Starch — Its composition answers to the formula 

 ^Q6jjioQ5y._,_3 Qjji.^ ^j. ^^.j^gj^ ^^.-^^^ ^^ jQQo ^ (JYV'O^ Musculus how- 

 ever showed, in 1861, that by the action of dilute acids or of Diastase, 



' Die Sturkeiorner, Zurich, 1858. 4°, also may be foimd in my paper Ueber Starke 



W. Nageli, Stdrkeijrupj)e, etc., Leipzig, iiiid CeUuhit — Arc/iir der Phai-mucie, 196 



1874. (1871) 7.— F. A. F. 



" Further particulars on this c^uestiou 



