CHEMISTRY OF DISEASE. 39 



ences will be observed. In some cases of gangrena sicca, 

 an analysis would show that the potatoe was almost con- 

 verted into starch. In other cases, when the potatoe is 

 fresh and simply hard, it would show a great deficiency 

 of starch ; but, if we took the produce of an acre, I have 

 no doubt that the total quantity of starch in the whole space 

 would be found to be enormously deficient. 



(149.) The following are the results of two analyses of 

 diseased tubers, which were so thoroughly rotten that the 

 mass was only held together by the skin. They were so 

 soft that they required no grating, and smashed under 

 slight pressure. 



I. II. 



Fibre . . . 4 -4 4 '6 



" Ash ; '. ' . 7 ' 2 '2 



Starch 21 '4 



L-41 



2* 



21-6 



Albumen, gum, &c. . 1 '5 ) 



Ash -3 \ 



Water : . ; - .'v .-,;/ 72'0 71'8 



100-0 100-0 



(150.) In this case the fibre was not the cellular tissue, 

 or fibre of the potatoe proper, but that of the peel. We 

 thus find that that important element of the plant was ma- 

 terially diminished. In this way the chemical examina- 

 tion of the diseased root tallies with the anatomical. When 

 the tubers were only partially diseased, I found as much 

 as seven per cent, of fibre. 



(151.) The quantity of starch in relation to the entire 

 mass was above the average even of good potatoes, which 

 I attribute to three causes : first, to the evaporation which 



