220 Agricultural Chemistry. 



the power of bringing about the same changes as are produced 

 by plant diastase, that is, the conversion of starch into the sugar, 

 maltose. This change begins in the mouth and continues for a 

 limited time in the stomach, or until the gastric secretions es- 

 tablish an acid reaction in the stomach contents. When this is 

 established, salivary digestion ceases. The proteins and fats are 

 not attacked by the salivary secretion. 



Euminants, whose feed usually contains much starchy material, 

 secrete enormous quantities of saliva. It is estimated that oxen 

 and horses secrete from 88 to 122 pounds daily. This serves the 

 additional important function of properly preparing the food 

 for swallowing. 



Gastric digestion. The food after mastication passes down 

 the gullet into the stomach. In the case of the horse and pig the 

 stomach is a single sac, and true gastric digestion begins at once. 

 In ruminants, as the ox and sheep, the stomach consists of four 

 divisions, or sacs, and not until the fourth is reached, does gastric 

 digestion proper begin. These sacs may be considered as en- 

 largements of the oesophagus and primarily for the storage of 

 the bulky materials consumed by these classes of farm animals. 

 The four divisions are the paunch, honey-comb, many-plies and 

 rennet, or what the anatomist has called the rumen, reticulum, 

 omasum and abomasum. The capacity of these cavities in the 

 ox is, on the average, not far from 50 to 60 gallons, about nine- 

 tenths of the space belonging to the paunch. It is in the paunch 

 that the food is first stored, only the finer portions being carried 

 by what is known as the oesophagal groove to the third stomach, 

 and finally from this compartment into the fourth and last di- 

 vision. From the paunch the food is returned to the mouth 

 where it is more finely ground before passing to the fourth stom- 

 ach for digestion. This is what is termed ''chewing the cud." 

 In the paunch salivary digestion probably continues, as well as 

 other fermentations induced by various micro-organisms. Here 

 possibly a partial fermentation of cellulose by bacterial enzymes 

 begins. 



