Effects of high-voltage cathode rays on aqueous solutions of tryptophan, tyrosine, phenylalanine and cystine.

1. Results for the copper and zinc contents ofeye tissues of perch, trout, and frogs are presented. The results of Leiner & Leiner (1944) for zinc in perch and trout are confirmed. 2. Most of the zinc, and half the copper, of the perch choroids is bound in non-ionic form to the pigment-protein fraction of the tissue. 3. The absorption spectra of pigment-protein suspensions from perch and frog eyes differ from those of cattle eyes. 4. On incineration, the perch pigment-fraction was found to leave about 10% of the dry weight as ash. Calcium, iron and strontium were constituents of this ash, but almost half is zinc (calculated as metal). 5. The association between zinc and melanin pigmentation is discussed.