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EXTRACTS FROM THE JOURNALS. 



ON THE POTATO DISEASE. 



j^ Communicated to the London Lancet by Andrew Ure, M. D., F. R. S.] 



The vague and contradictory statements concerning the nature 

 of this calamitous visitation of Providence, as well as the direc- 

 tions for the treatment and preservation of the tubers, generally 

 impractible and preposterous, which have recently issued in vast 

 variety from the press, do little honor to economic chemistry. It 

 is needless to notice all the notions and schemes which have eith- 

 er officially or spontaneously been projected. Only two of these 

 deserve comment : the first, as coming from a great master in sci- 

 ence, the second, as emanating from the Irish commissioners. 



Professor Liebig imagines the essence of the disease to consist 

 in the conversion of the albumine, a usual constituent of healthy 

 potatoes, into caseine, a principle which, by its great instability 

 of composition, is supposed to cause the potato to putrefy rapidly. 

 I have subjected this opinion to the test of experiment. Perfectly 

 sound potatoes, as also diseased ones, were sliced or grated, and 

 separately digested in a very dilute alkaline ley at a blood heat. 

 The infusions, when cool, being filtered and faintly acidulated 

 w^ith dilute acetic acid afforded respectively a like proportion of 

 caseine-looking flakes. It would thus appear, from this mode of 

 testing, as prescribed by M. Dumas, in the seventh volume of his 

 " Traite de Chimie," that sound potatoes contain as much caseine 

 as unsound. 



Professor Liebig's plan of preserving diseased potatoes is found- 

 ed on the above notion, and consists in cutting them into slices 

 one quarter of an inch thick, and steeping them twenty-four or 

 thirty-six hours in dilute sulphuric acid. On this proposal I need 

 make no comments, as it has no chance of being practised beyond 

 the precints of Giessen. 



In the PharmaceMtical Journal for October last, I inserted a few 

 observations on diseased potatoes, chiefly with the view of show- 

 ing, that till the putrefactive stage commences, the potato had the 

 same acidulous reaction as in the sound state, but that then a por- 

 tion of ammonia made its appearance, as was proved by its alka- 

 line action on litmus paper, and by its coming over in distillation. 

 That brief notice was written while I was at a distance from home 



