PHYSIOLOGY OF DIGESTION 39 



to sugar in the mouth, but it acts upon the starch in the 

 oesophagus and until it reaches the true stomach when the con- 

 version is arrested until the food reaches the small intestine. 

 The ferments which change starch to sugar are alkaline and the 

 gastric juice being acid, stops this conversion until the food 

 reaches the small intestine where the alkaline ferment amylopsin 

 completes this change of starch to sugar. 



Colin places the daily secretion of saliva in the horse at 84 

 pounds and in the ox at 112 pounds, though the amount will 

 depend upon the dryness of ' the food consumed. Hay absorbs 

 more than four times its weight of saliva, oats rather more than 

 their own weight, and green fodder half its own weight. 



4. Deglutition or swallowing. This is brought about by means 

 of the tongue, some of the muscles of the throat and by the 

 wave-like contractions of the oesophagus (gullet), which ends 

 at the stomach. 



Some animals prepare their food into round masses, called 

 boluses, before swallowing. The boluses of the ox are about 

 two or three inches in diameter; those of the horse are one-half 

 that size. 



The construction of the oesophagus of the horse is different 

 from that of the ox and sheep. It is very narrow and composed 

 of a thick, rigid muscular coat at its termination. The oesopha- 

 gus of the ox and sheep is coated with a thin muscular coat 

 which stretches easily and because of this, these animals can 

 swallow bulky material that would choke the horse. 



5. Stomachal Digestion or chymification. This step refers to 

 the food materials being converted into chyme, which is a liquid, 

 or semi-liquid, mass into which the food in the stomach is 

 changed by the action of the gastric juice, aided by the churning 

 motion produced by the muscular wall of that organ. When 

 in the stomach the food is not only rendered more liquid or 

 poultaceous by the gastric juice as a whole, but, by the chemical 1 

 ferment, pepsin, the insoluble protein is changed into soluble 

 peptone. 



The stomach of the ox always has food in it ; that of the horse 



