130 BOARD OF AGRICULTURE. 



tion. The second contains bodies more easil}' digestible, and have 

 been termed extractive carbohydrates. 



Woodfj fibre is celhilose more or less pure, and is that part of the 

 plant which is left after it has been treated with a series of solvents, 

 as dilute sulphuric acid, weak solution of potash, ether, alcohol, etc. 

 The substance thus obtained, contains more or less cellulose accom- 

 panied by an incrusted hard substance called lignin, which contains 

 .55 per cent, of carbon while cellulose only contains 44 per cent. 



It was thought that woody fibre was not at all digestible, but this 

 has been proved an error, as no inconsiderable amount of it can be 

 utilized b}' animals, especially the ruminants. Cellulose in the early 

 stages of growth is indeed nearlj^ as useful as substances belonging 

 to the second class. The second class comprises extractive carbo- 

 hydrates, which are represented in plants by starch and sugar. 

 Thej' are all more or less readih* attacked b}- chemical reagents, and 

 are digested with facility. In composition thej^ are nearly identi- 

 cal. All these bodies are easily- converted into glucose, a kind of 

 sugar. 



Fats. The fatty substances found in plants have a composition 

 which closety resembles that of animal fats. Fat does not exist in 

 large quantities in most fodder material ; varying between about one 

 to three per cent. The amount of fatt}- substance indicated in 

 anahses as being present in a plant is generally 'somewhat exagger- 

 ated, as the ordinary- method employed for its determination gives 

 results which are too large. 



Mineral Substances. The salts found in plants are generally 

 those most needed by the animal. It may sometimes happen that 

 they are deficient in quantit}-. Phosphates of lime must at times be 

 added to the rations for growing animals ; powdered bone-ash is 

 very good for this purpose. 



Digestibility of Fodder. 



It has been found by numerous experiments, for which we are 

 mostly indebted to German chemists and ph3'siologists, that the 

 various substances found in the ordinary fodder given to animals are 

 not totally digestible. The digestibility of food varies, for several 

 i-easons ; our domestic animals have different digestive aptitudes ; 

 the ruminants, for instance, can utilize more easil}' coarse woody 

 fibre than animals having a simpler digestive apparatus. 



