MAINTAINING FARM ANIMALS 59 



periods on a diet containing no fresh vegetables or meat, scurvy is 

 apt to result, even tlio an abundance of the common nutrients is fur- 

 nished. The addition to the diet of fresh vegetables readily prevents 

 this disease. In districts of the Orient where the inhabitants live 

 mainly on polished rice, there is often found a serious disease known 

 as beri-bein, characterized by general weakness and even paralysis. 

 Where unpolished rice, carrying the germ and part of the husk, is 

 eaten instead, this disease is not found. In experiments by various 

 scientists a similar condition has been produced in animals fed almost 

 exclusively on polished rice, while the unpolished grain did not have 

 such an effect. Tho many attempts have been made to determine the 



Fig. 16. — Commonly Unappreciated Substances Are Needed for 



Growth 



Hoth rats were fed "balanced rations" containing an abundance of suitable pro- 

 tein and mineral matter. The rat on the right, given butter fat in addition, grew 

 tluiftily, wliile the one on the left, fed cottonseed oil, wliich lacks the mysterious 

 substance present in butter fat, failed to grow. (From McCollum, Wisconsin 

 Station.) 



mysterious substance in the rice husk or germ which exerts such a 

 marked influence on health, but little is yet known regarding its 

 composition. 



Another important development in recent years has been the find- 

 ing that some of the substances included in the ether-extract, or 

 so-called "fat," of feeds are necessary to the well-being cf animals. 

 Animals fed upon feeds which contain an insufficient amount of these 

 unknown substances fail to grow and eventually die. If there is 

 added to the same ration some food which is rich in these materials, 

 such as butter fat, for example, normal growth can then be made. 

 These substances are not true fats, but compounds of unknown nature 



