The distribution of glycogen in the regions of the amphibian gastrula; with a method for the micro-determination of glycogen.

IANDERSTR0M-LANG AND HOLTER [1931] have described a micro-technique of great beauty, which they have used, amongst other things, for the estimation of reducing sugars [1933]. With the help of this technique, the Pfluiger [1904] method for the quantitative precipitation of glycogen was adapted to the estimation of small amounts of this substance. A number of difficulties were met with, and the experimental procedure is given below in some detail, as it was found that slight alterations in the method might cause considerible errors. Until a short time ago it was maintained by histologists [e.g. Woerdemann, 1933] that whereas the neural plate of the amphibian gastrula was rich in glycogen, the mesoderm, which is formed by invagination of the neural plate ectoderm, contained almost none. It has been suggested by Pasteels [1935], however, that the mesoderm does in fact contain glycogen, but that it is washed out of the cells during the fixing process. This suggestion is supported by Pasteels by experimental evidence which is shortly to be published. When the method for the micro-estimation of glycogen had been satisfactorily worked out, direct chemical measurements were made of the glycogen contents of various regions of the gastrula, which were isolated by dissection.