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Twenty-nine samples of fur, hair. wool and feathers have been irradiated with a Sunlamp (A max. 310 nm) and with a 2 kW mercury vapour lamp emitting mixed U.V. and visible radiation resembling sunlight. Photodegradation is accompanied by progressive yellowing when irradiated with the Sunlamp. It is accompanied by bleaching followed by yellowing, or by bleaching throughout irradiation if the initial yellowness is high, when exposed to the 2 kW lamp. A group of nine fur and hair samples, representing four different orders of mammals, are the most sensitive to yellowing, followed by a group of ten wool and hair samples from the Artiodactyla and finally by the feather keratins which are less susceptible than the a-keratins. Amino acid analysis of the keratins before and after Sunlamp irradiation shows strong correlation of yellowing both with the initial concentration of tryptophan and with its destruction during irradiation. Similar correlations of yellowing with destruction of other amino acids are less significant. Preliminary washing with non-ionic detergent increases susceptibility to U.V. yellowing.

In extension of previous work (Gillespie and Lennox 1953), the conditions under which proteins may be extracted from washed Merino wool have been further examined. Approximately 65 per cent. of the wool can be dissolved by a 40-min extraction at 50�C with O�1M thioglycollate at an initial pH of 12� 6. Electrophoresis at pH 11 in thioglycoIlate-glycine buffer indicated the presence of seven minor and one major component, the latter amounting to 41 per cent. of the wool. The minor components can be completely removed from the wool by five 2,O-min extractions with O�1M thioglycollate at an initial pH of 10�5. Extraction of the residue at pH 12�3 yields the major component. This moves as a single peak on electrophoresis between pH 8�0 and 12�0 in the presence of various buffers. It has a mobility of -7�2 X 10-5 cm2 V-I sec- I at a protein concentration of 0�5 per cent. in thioglycollate-glycine buffer of ionic strength O� 22 at pH 11� O. At higher protein concentrations there is anomalous behaviour on the descending boundary and tills can be prevented by increasing the ionic strength or replacing thioglycollic acid with mercapto-ethanol. The ascending pattern is unaltered by these changes or by increased protein concentration.

Solutions of the thioglycollate-reduced wool keratin preparation, "component 2" of Lennox (1953, 1955), show abnormal electrophoretic behaviour. New, faster moving peaks appear in the descending electrophoretic pattern at protein concentrations exceeding 0·5 per cent. which are attributed to an aggregation-disaggregation reaction. They are eliminated by increasing the ionic strength to 0·5, or by lowering the protein concentration to 0·4 per cent.The protein is modified by storage, both in solution and in the solid state, the modification being favoured by increase in temperature and manifested by a fall in relative viscosity of the solution together with a corresponding increase in mobility. The mobility increases only slightly as the pH is raised from 7 to 11, but it increases steeply at higher pH values.The intrinsic viscosity is about 0·2 in the pH range 8-10.