480 On the Composition of Linseed Oil- Cake, 



no nitrogen, it is obvious that the cake must be richer than the 

 seed in albuminous principles in the exact proportion of the oil 

 which it has lost by pressure. Given, then, the composition of 

 any sample of seed, and the quantity of oil which is expressed 

 from it, we have by the simplest calculation the composition of 

 the cake. In the present inquiry the order of procedure has 

 been reversed : instead of starting with the examination of linseed, 

 and speculating from the results upon the necessary composition 

 of the cake produced, I have applied myself first to ascertain 

 whether, in samples of cake taken carefully but indiscriminately 

 from commercial sources, there existed chemical differences suffi- 

 cient to account for the variations in feeding qualities observed 

 by the farmer. Not disputing, as I before said, that such supe- 

 riority of one sample over another was a fact, it yet seemed 

 gratuitous in the outset to allow that it resulted from difference 

 of composition. 



There are indeed two distinct circumstances which might influ- 

 ence the value of cake, independently of its chemical characters : — 

 the flavour, which is more or less agreeable to stock, and the 

 state of division — the fineness or otherwise to which the seed is 

 ground. To this latter circumstance, in all probability, very 

 great differences in the feeding properties of specimens of cake 

 might with justice be referred. Mr. H. S. Thompson published 

 some time ago experiments made by him upon the relative merits 

 of using linseed whole and crushed. 



He found that of linseed used in its entire state, a very con- 

 siderable proportion passed through the stomach of the animal 

 undigested, being present in the dung, and a})parently in an 

 unaltered condition. The same result in kind, though not in 

 degree, might be expected to occur in the case of linseed-meal 

 of various degrees of fineness, and with greater reason in cake, 

 the particles of which in addition are, by the extent of pressure 

 to which they have been subjected, closely compacted together. 



Both these causes of variation — the mechanical condition of 

 the cake and its flavour — lie, however, out of my province, which 

 is confined to the chemical composition of the substance in 

 question. 



1st., then, we must inquire. Is there any real difference in 

 the chemical composition of various cakes ; and if so, 

 does the distinction apply to those of different manu- 

 facture or origin ? 

 2nd. Is the difference (supposing there to be any) sufficient 



to account for the observed effects in feeding ? 

 And 3rd. Is it to be attributed to adulteration, or to neces- 

 sary variation in the composition of the seed ? 



