PHYSIOLOGY OF DIGESTION 



37 



contact. The dissolving of starch, which is insoluble in water, 

 by malt is an illustration of this kind of ferment. It is this class 

 of ferments upon which the digestion of the food depends. 

 These ferments change the insoluble compounds into compounds 

 which are readily absorbed into the blood. All the changes of 

 food in digestion are probably brought about by the action of 

 ferments or dilute acids. Examples of these ferments are: 



Solution 



Saliva 



Gastric 

 Juice 



Bile 



Acts on 

 Starch 



Forms 

 Maltose 



Proteids Peptones 

 Coagulates Milk 



Emulsifies Fats 



Accelerates Action of the 

 bowels 



The several steps of digestion follow : 



i. Prehension, or conveying food to the mouth, differs ac- 

 cording to species. The horse uses the lips a great deal in 

 gathering food. In feeding in the stall, the horse collects the 

 food with the lips and when grazing, cuts off the grass with the 

 teeth, drawing the lips back so as to bite close to the ground. 



The Ox has no teeth in the upper jaw and it seizes food with 

 the tongue. In grazing the tongue is extended and curled 

 around the grass, which is thus drawn into the mouth and taken 

 off by a swinging motion of the head as it passes between the 

 incisor teeth (teeth of the lower jaw) and the dental pad (pad 

 of the upper jaw). 



The Sheep has no teeth in the upper jaw. It has a divided 

 upper lip which permits the use of the teeth and dental pad in 

 grazing. Because of this divided lip the sheep can gather very 



1 Ellenberger (Herbivora). 



