Oil-cakes. 15 



mouldy or damp. Moreover, on the Continent the extraction of 

 the oil from the linseed is frequently aided by a degree of heat 

 which impairs the flavour, and consequently deteriorates the value, 

 of the cake. On the whole, greater care is bestowed on the manu- 

 facture of English cake than on that of cakes imported from other 

 countries. Besides, English cake is prepared only in a limited 

 extent, and always finds a ready sale ; no time is therefore allowed 

 for the oil still remaining in the cake to become rancid. Foreign 

 cakes, on the contrary, in passing through different hands before 

 they reach their final destination, often attain a considerable age, 

 which impairs the flavour and deteriorates greatly the value of 

 the cake, especially if it is kept in damp places. Like all organic 

 substances, oil-cake is subject to changes, which do not improve 

 its qualities. The fresher it is, the better it is adapted for feed- 

 ing-purposes. 



Foreign linseed-cakes, with the exception of American cakes, 

 are seldom so free from foreign seeds as English cakes, and 

 this no doubt is another reason why home-made cake is more 

 highly prized by the practical feeder. 



Mustard-cake. Mustard-cake is imported into England from 

 the Continent, and extensively used in the hop districts of Kent 

 as an excellent manure. This is the only safe use to which it 

 can be applied. But as it is much cheaper than linseed or rape- 

 cake, and resembles intimately rape-cake, it is now and then 

 mixed with this cake by unscrupulous dealers ; and instances are 

 on record that even pure mustard-cake has been sold as rape- 

 cake. 



When mustard-cake or rape-cake, containing much mustard- 

 seed, is made with cold water into a thick paste, and this paste 

 is kept for about six hours, it acquires the pungent taste and 

 strong irritating smell peculiar to mustard-seed. This pungent 

 taste and smell is caused by the volatile or essential oil of 

 mustard, which is produced under the influence of cold water 

 from myronic acid and myron, two inodorous and tasteless con- 

 stituents of mustard-seed. Myronic acid is peculiar to mustard ; 

 myron resembles in its chemical characters albumen, and, like 

 all nitrogenized substances, gradually changes myronic acid in 

 the presence of cold or moderately warm water and air into the 

 essential oil of mustard. At the temperature of boiling water 

 myron becomes coagulated, and in this state is incapable of 

 changing myronic acid into essential oil of mustard. 



Mustard-cake in a dry state has neither a pungent smell nor 

 taste. It resembles, indeed, in its appearance, smell, and taste, 

 rape-cake. If mustard-cake is kept, however, for some time in 

 the mouth, it tastes bitter, acrid, and becomes more and more 



