Section 2. 

 Stomach Digestion. 



Important digestive changes in the food of the lower animals 

 take place in the stomach. It is not a matter for surprise to find 

 that the size and shape of this organ varies with the species of 

 animal ; we should expect to meet with a simple stomach in the 

 dog, and complex arrangement in vegetable feeders. It seems 

 remarkable that any animal should possess a laboratory capable 

 of converting grass, hay, and grain into muscle and fat ; and it is 

 evident that the conversion of vegetable into animal tissues 

 must be a more complex process than the conversion of animal 

 tissues into the living structure of an animal body. But it is 

 curious to observe that a complex stomach for a vegetable feeder 

 is by no means a necessity ; the stomach of the ruminant and the 

 simple stomach of the horse could not be in greater contrast, 

 while the resulting laboratory processes are practically identical. 

 So far as vegetable food is concerned, it does not matter whether 

 the solution and absorption of its readily soluble matters comes 

 before maceration, or whether maceration precedes the extraction 

 of the readily soluble substances. If maceration comes first, as 

 in ruminants, bulky gastric compartments are provided for the 

 purpose, and the subsequent intestinal canal is small. If the 

 simple stomach comes first, bulky intestines for the purpose of 

 maceration follow ; in both cases ample provision is made for the 

 maceration necessary for the solution of the cell wall and fibrous 

 portion of plants. The dog, with its simple stomach and simple 

 intestines, offers no difficulty to our understanding. He lives on 

 flesh, and converts it into flesh ; it is not very clear why he has 

 both a stomach and intestines, for the whole process of digestion 

 is simple, and could be readily carried out single-handed by the 

 intestines. In fact, the stomach of the dog has been removed 

 experimentally, and the animal remained in health. 



For simplicity in construction the stomach of the dog occupies 

 one end of the scale, for complexity the gastric reservoirs of the 

 ox occupy the other, while between the two comes the stomach 

 of the omnivorous pig, partaking of some of the characters of 

 the carnivora and ruminant, and belonging to neither. 



Stomach Digestion in the Horse. 



The subject of stomach digestion in the horse has been worked 

 out by means of feeding experiments, as it has been found 



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