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Quarterly Journal of Microscopical Science, Vol s3-90, 381-390, Copyright © 1949 by Company of Biologists
1 Department of Physiology, Middlesex Hospital Medical School, London, W.1; Department of Zoology, King's College, London, W.C.2
1. A histochemical study has been made of alkaline phosphatase in the endoskeleton of dogfish embryos of 18-115 mm.
2. The distribution of phosphatase is compared with that of insoluble calcium salts.
3. Phosphatase was first noted in the chondrocytes and perichondrium at 47 mm. and in the cartilage matrix at 58 mm.
4. Calcification occurred first in the neural plates at 58 mm. and in the skull at 74 mm. No calcification was observed in zones devoid of extracellular phosphatase.
5. As the intensity of calcification increased the amount of phosphatase tended to drop.
6. It is concluded that in elasmobranchs, as in higher animals, extracellular phosphatase is an essential precursor of calcification.