128 TRACE ELEMENTS IN ANIMALS 



severe, results in the sloughing of the hoof. General loss of 

 condition involving emaciation and listlessness may follow, and 

 in the worst cases the animals may die. There may be lesions 

 in various internal organs, including the heart, liver, spleen and 

 kidneys. With affected poultry eggs do not hatch. Further, the 

 symptoms can develop in animals in non-affected areas when fed 

 with hay or grain produced in the affected areas. Because of the 

 popular opinion that these effects were due to alkali in the water 

 drunk by the animals, the disease was generally known as 

 'alkali disease', but more than 30 years ago careful work by 

 Larsen, White and Bailey (1912, 1913) showed that this con- 

 clusion was false and the cause of the disease must be sought 

 elsewhere. That this was to be found in poisoning by selenium 

 appears to have been first suggested in 1931 (see Byers, 1934). 

 First investigations showed that selenium was present in the 

 soils of the affected areas and that wheat grain from such areas 

 might contain from 10 to 12 p.p.m. of selenium (Robinson, 

 1933). Nelson, Hurd-Karrer and Robinson (1933) found that 

 wheat appeared to grow normally on soil to which 1 p.p.m. of 

 selenium had been added in the form of sodium selenate, but the 

 grain from this wheat was toxic to white rats fed with it, re- 

 tardation of growth, and finally death, resulting. Schoening 

 (1936) developed the typical symptoms of alkali disease in hogs 

 by feeding them with maize grown in the affected area. Two lots 

 of maize were used, one containing 5 p.p.m. the other 10 p.p.m. 

 of selenium. 



Further experiments on dosing animals with selenium leave 

 no doubt that this element is responsible for producing the 

 symptoms of alkali disease, and that this is, in fact, selenium 

 poisoning. The animals used include rats (Franke and Moxon, 

 1936), rabbits (Smith, Stohlman and Lillie, 1937), swine (Miller 

 and Schoening, 1938; Miller and Williams, 1940a), cattle, horses 

 and mules (Miller and Williams, 1940a). As an example of the 

 type of experiment employed may be cited one by Miller and 

 Schoening on swine. In this eight pigs about 4 months old were 

 separated into four pairs. All received a sufficient ration of 

 grain, but the four groups received different amounts of selenium, 

 the proportions of this, as sodium selenite in the ration, being 

 respectively 392, 196, 49 and 24-5 p.p.m. Four of the animals 



