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Two sheep were drenched each with 100 g of soil containing approximately 1 mc each of 60Co, 540Mn, 75Se, and 65Zn. Activities of these isotopes in blood, urine, and faeces were monitored at intervals over a lO-day period by gamma-ray spectroscopy. At the end of this period the animals were killed and a range of hard and soft tissue samples was taken for analysis. From the data obtained on blood and tissue samples taken at time of death, and from urine samples over the lO-day period, amounts of isotopes absorbed by the animals and amounts of isotopes originally held on the ingested soil were compared. The amounts of the isotopes absorbed by the animals from the soil, expressed as a percentage of an isotope held on the soil, were approximately: 75Se, 34 percent; 65Zn, 14 percent; 60Co, 1 percent; MMn, 0.4 percent.

The recent improvement in spectropolarimeters makes it possible to measure the Cotton effects of polypeptides and proteins between 185 and 240 rnp.Ir2 The helical conformation, quite unlike the coiled form, shows a strong trough and peak at 233 and 108 mp. The reduced mean residue rotations, [m']233 and [112']198, have thus been suggested as two measiires of the helicity in protein moleciiles. At present, poly-L-glutamic acid (PGA) in aqueous solution is providing the reference values for the two conformations. The reported value for [m']233 (helix), however, varies from -13,000 to -18,000, thiis making siich an estimation very inc certain.^ Such a wide variation in reported results is puzzling because t,he PGA samples have all been prepared by the same meth0d.l We offer a comparative stitdy of 4 samples from 4 laboratories; all stork solutions were

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