CHEMISTRY OF DISEASE. 4l 



them. The ash of fibre and starch is white, while that of 

 albumen is of a reddish tint from the presence of iron. 



(155.) Diseased potatoes are not, then, thoroughly de- 

 stroyed. They may indeed not contain all the elements 

 of food, and, therefore, are not fit for perfect nutrition ; yet 

 the starch may be turned to account for all the various 

 purposes for which that substance is employed. 



(156.) A great deal has been said about the extraction 

 of this principle, viz. starch, and ridicule has been at- 

 tempted to be thrown over the process ; yet, for the pur- 

 poses of fattening animals, and of conversion into dextrine 

 and sugar, its separation may be advantageously per- 

 formed. 



(157.) Dr. Ure has pointed out that sugar is to be found 

 in the diseased potatoes. This is an interesting fact, as 

 it explains the reason why diseased potatoes have so great 

 a tendency to sprout. The sugar may be determined by 

 fermentation or other suitable means. 



(158.) Mr. Rogers found butyric acid in rotten potatoes 

 which had been buried for three years one or two feet 

 deep, but it does not appear that it is found in the diseased 

 substance now under consideration. 



(159.) Diseased potatoes are especially liable to fermen- 

 tation : two or three placed in a bottle, and tied over with 

 a bladder, will give off gas to such an extent as to distend 

 the membrane and finally burst it. 



(160.) So prone are they to putrefaction, that I find that 

 when they are hermetically sealed with balsam of Canada, 

 still they evince the property of fermentation and evolve 

 gas. 



(161.) The diseased potatoe differs from the sound pota- 

 toe in its various ingredients. The only material left in 



