354 FEEDING WITH SUGAR BEETS, SUGAR, ETC. 



sidered. Digestion taken as a whole depends upon the mouth, gullet, stomach, 

 small and large intestines, and the several secretions. In the mouth, the lips, 

 teeth and tongue, all have special functions. Farm animals when living 

 under natural conditions, are compelled to hunt for their food; they thus take 

 more exercise and develop more muscle than when stall-fed. Ruminating 

 animals draw up their food with their tongue, which always has a rough sur- 

 face; the shape of their lips and teeth is such as to offer but little assistance 

 in collecting food. Horses on the other hand use their lips and with the 

 assistance of the incisor teeth on the lower jaw cut the grass or herbs found 

 in pasturage. Cattle when using their tongue give their heads a swinging 

 motion which breaks the tuft of grass held by the tongue and pressed against 

 the lips. The nutrient thus collected is crushed by the teeth on the lower jaw 

 against the hard bone-like substance of the upper maxillary. The cheeks help 

 considerably in either passing the semi-crushed or ground product from one 

 side to another, or holding it during mastication. 



It is to be noted that in nearly all the herbivorous animals the lower jaw is 

 much smaller than the upper. It frequently happens that when one side is 

 working, the other is separated nearly an inch. On the other hand, sheep- 

 grazing means that the field is eaten almost to the surface of the ground; the 

 horse is more wasteful, and cattle still more so. In the mouth the various 

 salivary glands secrete special fluids of different consistency and composition, 

 which each have special functions to fulfill; taken collectively they are known 

 as saliva, and contain about 1 per cent, solid matter. 



The saliva proper consists mainly of water; besides mucus, it contains albu- 

 min, alkaline carbonates, alkaline chlorids, alkaline phosphates, and a sub- 

 stance known as ptyalin, a ferment having a very important function to fill, 

 which consists in converting starch into sugar, a transformation that occurs 

 mainly in the stomach in presence of other secretions. After mastication, the 

 food is soon shaped into a rounded mass or bolus,* which form allows its pas- 

 sage into the throat with the least possible difficulty. The time or duration 

 of mastication, varies with the animal; practical experiments appear to show 

 that a horse needs one and a half hours to masticate four pounds of hay, dur- 

 ing which interval there will be formed about sixty boluses. The horse in its 

 normal state can bring its teeth together some seventy times per minute, when 

 there is an ample flow of saliva. The periods change, and Colin' s experiments 

 show that when all the saliva is allowed to pour into the mouth, the duration 

 of mastication for one bolus is about 32 seconds; if only one of the parotid 

 glands is open, the duration is 34 seconds, and with both closed, the period is 

 about 75 seconds. During these periods the number of strokes of the teeth 

 vary from 38 to 74. It is not necessary to give similar examples for other 

 animals. For the horse it was found that the saliva secretion amounted to 

 about 12 Ibs. of saliva per hour during hay feeding; with green food about 

 half its weight of saliva is needed. 



*The size of a bolus varies with the animal; for an ox it is twice the size that it is for 

 a horse. 



