66 Cambridge Philosophical Society. 



The mean of the former is 4" 19 per cent, of ash, that of the latter 

 5*68, making an excess of 1*49 per cent, arising from loss of organic 

 matter. 



The ultimate analysis of the unsound portion afforded the follow- 

 ing results : — 



I. 155 milligrammes gave carhonic acid 238 - 5, water 98. 

 II. 132 ... ... ... 202 ... 78. 



III. 163 ... ... ... 251, water not esti- 



mated. 

 Mean of two analyses for nitrogen, after the method of MM. 

 Varrentrapp and Will, 1"23 per cent. 



These data furnish the following summary : — 



I. II. III. 



Carbon .... 42-09 41-73 41-99 



Hydrogen .. 7'02 6-56 7'02 



Nitrogen 1'23 1-23 123 



Oxygen 43-98 44-80 44-08 



Ash 5-68 5-68 5-68 



100-00 100-00 10000 



The analysis of the sound potato, by Boussingault, is as fol- 

 lows : — 



Carbon 44- 1 



Hydrogen 5*8 



Nitrogen 1*2 



Oxygen 43-9 



Ash M) 



100-0 



The object of the second part of the communication is to show, 

 that, while Boussingault's analysis of the sound potato may be ex- 

 pressed by an empirical formula, representing the elements of pro- 

 teine, starch, and cellulose, the analysis of the tuber, after under- 

 going the action of the late prevalent disease, admits of no such so- 

 lution ; but may be expressed by an empirical formula, representing 

 proteine, starch, and butyric acid, with a very large excess of the 

 elements of water. 



Butyric acid has been found in the diseased potato by Mr. 

 Tilley ; but the author's principal object is to connect the changes 

 developed by his analyses with the researches of Erdmann, Mar- 

 chand, and Scharling, on the germination of seeds and tubers. 

 These researches are totally independent and irrespective of the dis- 

 ease in question, whilst it is clear that the same changes occur in 

 both cases. After reviewing the physical circumstances with respect 

 to soil and culture, which have proved remarkably favourable to the 

 development of the morbid changes, the author arrives at the gene- 

 ral conclusion, that the disease in question essentially consists in an 

 unnatural tendency to premature germination. 



