and the different amylaceous Substances of Commerce. 369 



he has raised. I sincerely desire that he may attain it, for the 

 interest of truth and also for my instruction : this avowal will 

 suffice without doubt to make this estimable author appretiate 

 the motives which have induced me to publish these reflections. 



P.S. I have just become acquainted with a work entitled 

 Memoir on the Structure of the Potatoe, by M. A. Villars, Dean 

 of the Faculty of Medicine in Strasbourg, correspondent of the 

 Institute, &c. 



This work, inserted in volume xlii. of the General Journal 

 of Medicine i at present edited by Dr. Sedillot, containing 

 some experiments and views calculated to throw some light 

 on the question which I have treated with relation to the 

 homogeneity of the fecula, as well as on the priority of mi- 

 croscopic observations of this nature, I have thought it useful 

 to extract from it the following passages at the conclusion of 

 my Memoir. 



(Paragraph 19.) " The flour ofpotatoeis formed of ovoid 

 globules from T \ T) to J^ of a line in diameter, and about a 

 third more in length. 1 had observed them at Grenoble, 

 noted and drawn them in 1802, perfectly conformable to what 

 I observed at Strasbourg in 1810. I again took to this pur- 

 suit with more details and variations with new microscopes. 

 These globules are smooth, brilliant and milky, like globules 

 of mercury. 



" § 20. The globules of the fecula of potatoe crushed on the 

 glass as much as possible with a steel blade, are smaller by 

 half or two thirds, and are rather square or irregular, but 

 always smooth. 



" § 21. The same globules cooked in the potatoe are about 

 a third larger, more rounded, and less even, not shining, but 

 as if cracked or split on their surface, being seen of the same 

 size at a hundred diameters. 



" § 22. The same globules seen through a very thin slice of 

 about T \jth of a line thick, taken in a frozen potatoe, appeared 

 to me less by one-half, surrounded with water and as it were 

 deliquescent. I could then see, with the same lens, the tissue 

 of the potatoe or the fibrin which contains the globules ; they 

 are disseminated through it by groups in contact but not ad- 

 herent to the meshes of the tissue. 



" § 23. I dried on glass and on plates the fecula of potatoe, 

 in a stove and in a sand-bath, until the globules began to 

 redden. They lost a little of their size and a little of their 

 brightness. The light then penetrates them only towards the 

 centre, whilst the circumference appears opaque, as if they were 

 bubbles of air seen by the microscope. In this state, I crushed 



Vol. 68. No. 343. Nov. 1826. 3 A them 



