HISTOCHEMICAL STUDY OF PHOSPHATASE AND GLYCOGEN IN FETAL HEADS

¹ College of Dentistry, University of Southern California, Los Angeles and the William G. Kerckhoff Laboratories of the Biological Sciences, California Institute of Technology, Pasadena, Cal.

1. Fetal rat heads from the 13th to 20th day of gestation were studied histochemically for phosphatase and glycogen.

2. The distribution of these substances at different fetal ages is described.

3. Three classes of tissue are distinguished: those which contain phosphatase but no glycogen, those which contain glycogen but no phosphatase, and those which contain both phosphatase and glycogen.

4. All the calcifying tissues belong to the third class, the incisors possibly excepted.

5. In non-calcifying structures which appear to belong to the third class it was found that the phosphatase and glycogen are in actuality separated into morphologically different layers.

6. Three human fetuses showed distributions of phosphatase and glycogen in essential agreement with the above findings.

7. It is concluded that both glycogen and phosphatase are involved in normal calcification, and the most probable mechanism of their interaction is discussed.