Abstract
Results obtained from a study of the development of connective tissue in amphibian embryos, as presented in a previous communication, 1 show that the process is essentially in agreement with the intercellular theory of connective tissue formation.
The previous observations were made on preserved amphibian material. It has been found possible this spring to demonstrate the presence of a primary ground substance in various stages of living amphibian embryos. Living embryos, ranging from a late gastrula stage up to the free-swimming embryo, have been dissected under the binocular microscope and it has been possible in all stages to show, as was previously demonstrated in the prepared material, that an homogeneous, intercellular, gelatinous material, permeates various regions of the embryo. This substance as seen in a living embryo is perfectly transparent and is, therefore, difficult to detect under the binocular or under a compound microscope equipped for ordinary illumination. It can, however, be readily studied with a microscope equipped for dark field illumination and numerous observations on this material have been made in this manner.
The present observations on the ground substance in living amphibian embryos, therefore, confirm those previously obtained with prepared material and show conclusively that the primary substance in connective tissue formation is a secreted, intercellular material.
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