Nutrition Studies. 69 



salt was supplied — evidence that not the lack of sodium but the 

 lack of chlorin was responsible for the troubles. The break- 

 down due to the lack of salt usually occurred after calving when 

 the milk flow -was heavy, and generally the cows giving the 

 largest amount of milk were the first to show distress. 



Babcock points out that the amount of salt required in the 

 ration will vary greatly in different localities. Soils which con- 

 tain large quantities of salt doubtless produce feeding stuffs 

 containing more salt than those poor in this ingredient ; and again 

 the water of streams and wells varies greatly in its salt content. 

 These facts doubtless account for the disagreement among experi- 

 menters in different parts of the world as to the importance and 

 value of salt. Cows in milk and sheep show the greatest need of 

 salt ; fattening cattle, horses, dry cows, and stock cattle require 

 less salt; and pigs but little. 



92. Light. — Graffenberger,^ experimenting with young and full- 

 grown rabbits confined in a dark room for long periods, found 

 that the hemoglobin content of the blood was lowered and the 

 amount of blood in the body was decreased by from 9 to 22 per ct. 

 thru such confinement. An increased formation of fat was ob- 

 served, which was especially marked in the case of mature ani- 

 mals. If confined too long in the dark the increase was relatively 

 small. Graffenberger does not advocate entire darkness for fat- 

 tening animals, but rather the partial absence of light, which tends 

 to quiet and hence favors fattening. The development of the skel- 

 eton and the liver is retarded by darkness, so that the prolonged 

 absence of light has a deleterious effect on animals. Darkened 

 quarters are not advisable for fattening animals fed for lon«i 

 periods, and in no case for young ones designed ultimately for 

 work, milk production, or breeding. 



93. Quiet.- — Farm animals are creatures of habit, and once ac- 

 customed to a routine of living show unrest with any change. 

 The feed stable or feed lot should be free from disturbance, and 

 the administration of feed and water should be uniform in time 

 and manner. Animals soon learn when these are to occur, and as 

 feeding time approaches the secretions begin pouring from the 

 various glands in anticipation of the coming meal. The system of 

 feeding and watering and the character of the rations should be 

 changed gradually and only for good cause. In feeding opera- 

 tions a changing period is usually a losing period. 



' Aroh. Physiol. (Pfliiger), 53, 1893, p. 238. 



