154 DIGESTIVE POWERS OF THE HORSE AND PIG. 



the epidermis of the top or side of the seed witli"ix slight 

 report, like that of a popgun — and forces back, in fact 

 turns outside in, the swollen and now white and spongy 

 mass into which the horny part is changed. In this 

 state the corn is soft and agreeable to eat, more easy of 

 digestion, and is largely consumed. The increase of bulk 

 by this heating process is' so great that one barrel of 

 pop-corn will produce sixteen, and of rice-corn, which is 

 a small seed, thirty-two barrels of poppet? corn. 



It will occur to the reader, from what I have said of 

 the internal structure of Indian corn, that the flour 

 which is obtained from the several varieties will be more 

 or less yellow, according as the proportion of the coloured 

 horny part is greater or less. Hence the white Tusca- 

 rora corn, which contains scarcely any horny matter, 

 gives a whiter flour than almost any other variety. 

 This is the variety, therefore, which is principally made 

 use of for the manufacture of starch, and for the adul- 

 teration of wh eaten flour. 



As the direct fattening property of seeds is believed to 

 be intimately connected with the quantity of oil they 

 contain, I may mention in this place an interesting 

 physiological fact, communicated to me by Dr Charles 

 Jackson of Boston, which is susceptible of an important 

 practical application. The horny part of the corn, he 

 informs me, is not digested by the horse, though it is 

 readily digested by the pig and by fowls. The econo- 

 mical value of a food, therefore, as I have elsewhere 

 explained, cannot be judged of solely from its chemical 

 composition.* 



On our arrival at Rome, the neighbourhood of the 

 station was crowded with people who were waiting to 

 get a peep of Mr Clay, whom we had picked up at Utica 

 on his way to Syracuse. Our train had now swelled to 



* See the Author's Lectures on A(jricultural Chemistry and Geology, 

 2d edition, p. 1045.^ 



