A ee ee DIFFERENTIATION OF GASTRULAS AND FEATHER GERMS1011 ; 4 oe _* , : oe ‘io : 3. M. Reyss-Brion, L'effet des rayons X sur les potentialities respectives de Vectoderme compétent et de son indicateur naturel chez la Jeune gastrula d’Amphiblen, Arch. Anat. Microse. Morph. Exp., §3(4): 397-465 (1964). OPEN DISCUSSION SCHJEIDE: Let me make a remark, It has been found that the bone matrix which has been completely decalcified can serve as an inducing agent for formation of bone by surrounding mesenchymal cells. Nothing is being secreted by the dead bone matrix, and the present thought is that it merely presents a surface which the mesenchymal cell recognizes and that this is enough of a message. In your case do you see any secretion from the inducing tissue of chondroitin sulfate or collagen? REYSS-BRION: No secretion. LINDENBAUM:I cannot help reacting to the suggestion of some esoteric inducing factors for collagen. The idea of a dead matrix inducing the later formation of bone apatite I think should not be thought of as having anything to do with biological systems. SCHJEIDE: Well, if you irradiate the bone very heavily to cause derangement of the matrix proteins, you do not get induction. And on the other hand, a sponge will not induce bone. The information contained in a dead bone matrix may not be the true message, but itis a message that results in the production of normal calcification. LINDENBAUM:I think its a semantic difference, but I’m object- ing to the use ofthe word “message,” — unless you want to call a chemi- cal reaction that produces something out of something else “a mes- sage.” SCHJEIDE: I take the opposite view. BEAUMONT;Is there any evidence of a transfer oflabeled RNA or protein from the donors dermis to the epidermis? REYSS-BRION: We do not have any evidence of transfer of material because the two tissues were not separated at the final incubation, scree en earner ered '