290 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1935 



it has been found in plants growing in the vicinity of manufacturing 

 establishments that produce seleniferous waste products, and in soils 

 treated with fertilizers made from materials containing selenium as 

 an impurity (Stoklasa, 1922). The increasing use of selenium- 

 containing fungicides and insecticides in the United States raises a 

 question as to the danger of still wider distribution, although it has 

 not been shown that the form of selenium used in these materials is 

 readily available to plants. 



Before proceeding with the discussion of the absorption of se- 

 lenium by plants, it may be of interest to relate how and why we 

 know that the livestock disease of the Middle West is really selenium 

 poisoning. The discovery of the cause of this obscure and baffling 

 trouble, affecting the animals of certain restricted areas, constitutes 

 one of the romantic episodes in the history of agriculture. By en- 

 listing and combining the knowledge and experimental technique 

 of the soil chemist and the plant and animal physiologists, the prob- 

 lem has progressed from the discovery of the cause to suggestions for 

 control in a surprisingly short time. 



The existence of the disease has been known ever since the affected 

 States were opened for settlement. The most conspicuous symptoms 

 in horses, cattle, and pigs are the loss of hair, w^ith deformity and 

 eventual loss of the hoofs (pi. 1). Cattle lose the hair of the tail, 

 and horses both mane and tail. The animals are often emaciated 

 and lame, and those most severely affected die. Cattle and horses 

 may die of thirst or starvation because of the difficulty of getting to 

 food and water. If the toxic foodstuffs are removed from the diet, 

 the animals improve to a considerable degree but never seem to re- 

 cover entirely. In poultry the prison affects the eggs, most of which 

 produce weak, abnormal chickens or fail to hatch (Franke et al., 

 1934). 



The earliest reference to the disease seems to be a report of similar 

 trouble affecting Army horses at Fort Randall, Territory of Ne- 

 braska (now in South Dakota), in 1856. Later, the early settlers 

 in this region were confronted with the sickening and death of 

 their animals. Pathetic letters are on file in the Department of 

 Agriculture as far back as 1908, reporting the total loss in some 

 instances of herds of valuable animals and appealing for informa- 

 tion and assistance. The disease has thus interfered with the devel- 

 opment of some sections of the country, and in others it still consti- 

 tutes a serious handicap to farming. And all because too much 

 selenium occurs in these parts of the earth's crust ! 



Some of the farmers themselves concluded that the trouble was due 

 to something the plants absorbed from the soil. Scientists at the 

 South Dakota Experiment Station then began experimenting and 



