212 THE PRINCIPLES OF AGRICULTURE 



set even to these, the red globules being 

 mainly carriers of oxygen, while the white also 

 have restricted functions. 



2. The Food of Animals 

 2a . Kind of food 



367. Food may be either vegetable or ani- 

 mal. Many animals, as horses, cattle and 

 sheep, live on vegetables, or are herbivorous ; 

 while others, like foxes and wolves, eat animal 

 food only, or are carnivorous. The food of 

 the herbivorous animal has its nutritive prin- 

 ciples in a less concentrated condition, and the 

 herbivora are accordingly supplied with more 

 capacious digestive organs. The same holds 

 true of grain -feeders and grass -feeders among 

 the herbivora. The grain -fed horse has much 

 smaller stomach and intestines than the grass- 

 fed ox, and the well-fed domestic rabbit has a 

 much more spacious alimentary canal than his 

 wild ancestor. 



368. Artificial selection and forcing of meat- 

 producing animals has a similar effect. The 

 scrub ox, Texas steer and buffalo have light ab- 

 dominal contents, while the pampered short-horn, 

 Hereford, or black-polled ox has them heavy 

 and bulky. In the carnivora they are still more 



