TRACE ELEMENTS IN ANIMALS 133 



of the herbage from twelve teart localities was 33 p.p.m. of dry 

 matter in 1937 and 38 p.p.m. of dry matter in 1&38; the corre- 

 sponding mean values for eleven non-teart localities were 5 and 

 4 p.p.m. for the respective years. This finding strongly suggested 

 that molybdenum might be the cause of scouring, and this was 

 confirmed by administering doses of ammonium or sodium 

 molybdate to cattle when the symptoms of scouring were pro- 

 duced in a number of cases, although there was considerable 

 variation in the degree to which different individual animals 

 reacted to molybdenum. Scouring was also produced in cattle 

 and sheep turned into non-teart pasture dressed with sodium 

 molybdate. 



Hay and frosted herbage do not have the same effect as the 

 fresh material in inducing scouring. This appears to be due to 

 the fact that fresh herbage contains a much higher proportion 

 of the molybdenum in soluble form than does hay or frosted 

 material, and it would thus appear that it is the soluble fraction 

 of the molybdenum that is responsible for the effect on cattle. 



It has been mentioned that the teart soils occur on the Lower 

 Lias where this is directly exposed, but that such an area in 

 Glamorgan does not exhibit the properties of teart land. Lewis 

 (1943 a) has examined a number of Lower Lias soils in their 

 relation to teartness and finds that the teart soils contain about 

 20-100 p.p.m. of molybdenum in the surface horizon and are 

 neutral or alkaline in reaction. The soils of the Glamorgan area, 

 however, were found to contain only about 2-4 p.p.m. of 

 molybdenum, which explains why they are not teart in 

 character. 



Very interesting are the results of experiments made by Lewis 

 (19436) to examine the uptake of molybdenum from teart soil 

 by plants of a number of different pasture species. Ten pasture 

 grasses and two species of clover were used in these experiments, 

 the seeds being sown in pots of teart soil, four pots of each species 

 being used. The herbage was cut when it was about 3-4 in. high 

 and the molybdenum content determined. After a further period 

 of growth it was again cut and the molybdenum content in the 

 new sample determined. This procedure was repeated so that 

 four samples were obtained in all for each species. The results 

 are summarized in Table XVII. 



