132 TRACE ELEMENTS IN ANIMALS 



directly exposed and not covered by drift or boulder clay, there 

 are pastures which bring about the complaint of cattle known as 

 scouring. Cattle, on being turned into these pastures, develop 

 the symptoms of scouring within a few days. The symptoms are 

 described by Ferguson, Lewis and Watson (1943) as follows: 

 ; The dung becomes extremely loose and watery, yellowish green 

 in colour, bubbly, and has a foul smell. The animals become 

 filthy, their coats stare and they lose condition rapidly. Red 

 Devon cattle turn a dirty yellow and black beasts go rusty in 

 colour. Milk yields drop considerably.' Sheep are not affected to 

 the same extent, but the dung is very soft and the fleeces some- 

 times become stained. 



The principal area in which teart soils occur is in central 

 Somerset, but smaller areas occur in Warwickshire and Glouces- 

 tershire. It is to be noted that an area in Glamorgan in which 

 the soil is also derived from the Lower Lias does not exhibit 

 teartness. 



The effect of teart land on cattle has been known, according 

 to Ferguson, Lewis and Watson, for over a hundred years, and 

 has been attributed to a number of factors, including bacteria, 

 parasites, particular species in the herbage, water supply, poor 

 drainage, soil texture, a high proportion of non-protein nitrogen 

 in the herbage, and some particular chemical constituent 

 present in the herbage (Muir, 1936). Bacteria cannot be the 

 primary cause of scouring because the symptoms cease directly 

 the cattle are removed from teart pastures, while as regards 

 parasites there is no abnormally high number of these in affected 

 animals. Nor do the water supply, drainage and soil texture of 

 teart pastures show constant and characteristic differences from 

 non -teart areas. Ferguson, Lewis and Watson determined the 

 nitrogen fractions in herbage from teart and non-teart areas but 

 found no difference in the non-protein nitrogen of the two. 



These workers were thus led to investigate the last of the 

 suggestions listed above and made a spectrograpliic examina- 

 tion of a number of samples of herbage from different sources. 

 As a result they found one constant difference between the 

 samples from teart and from non-teart pastures, namely, in the 

 content of molybdenum, which was considerably higher in the 

 case of the teart herbage. Thus the mean molybdenum content 



