442 GERMINAL ORGANIZATION INDUCTION PHENOMENA 4 



However, this clear-cut exclusion of the RNA as the real inductor is not so far 

 supported by a study of Vahs (1957b), which bears on a quite different source 

 of xeno-inductors, bacteria. 



Gram-positive bacteria {Staphylococcus, Thermobacterium, Corynebacterium) were compared 

 to gram-negative ones {Escherichia, Proteus, Clirornobacterium). Pure cultures were agglomer- 

 ated by ethanol, washed, and implanted in the blastocoele. Gram-negative bacteria are 

 deprived of any induction power, while the gram-positive ones induce, in order of frequency, 

 balancers, free lenses, lentoids, and epidermal thickenings, i.e., inductions of an acren- 

 cephalic type, but of limited importance. The positivity of staining is due to a Mg-ribonu- 

 cleoproteic complex and the corresponding bacteria were submitted to agents capable 

 of suppressing this component, e.g., extractions by bile-salt solutions or by jVHCl, treatment 

 by ribonuclease, irradiation with bactericidal ultraviolet doses. Bacteria rendered gram- 

 negative by any of these procedure also proved to have lost their ability to induce. 



Striking as it is, this result is not yet sufficiently analysed to draw a definite 

 conclusion. The ribonucleic complex has not been isolated, tested for itself and 

 subsequently submitted to enzymatic digestion. As we have seen for other xeno- 

 inductors, ribonucleoproteins may appear to play the leading role, but the 

 analysis finally turns in favor of the protein moiety. 



To complete the picture, a few data concerning some other xeno-inductors 

 should be added. 



In the paper quoted p. 433 concerning the pituitary powder, it is mentioned that 

 a fractionation performed by the Tiedemann's has isolated a ribonucleoprotein 

 with a mainly deutencephalon effect — an agent already manifest in the whole 

 powder — and a protein fraction inducing trunks and tails (tritogenic) 



The work of the same authors (Tiedemann and Tiedemann, 1956 and 1957) 

 on the extract of chick embryos, a material presumably nearer to the true physio- 

 logical agent of induction, is especially interesting. It has first been found possible 

 to isolate two protein fractions, one acrogenic and the other tritogenic. Then, 7-9 

 day embryos have been homogenized and submitted to successive centrifugations, 

 precipitations and extractions. In certain samples, RNA could be eliminated by 

 phenol extraction, while in others, the nucleoproteins were precipitated by using 

 streptomycinsulfate. From the published results and according to a personal 

 communication, it appears that three different inducing agents exist in this 

 embryo extract. The first one exerts a tritogenic induction of mesoblastic character, 

 or nearly; when submitted to high temperature in alcaline conditions, its action 

 shifts towards the exclusive induction of a spinal cord; this agent is a protein, not 

 bound to a nucleic acid, and of a relatively low molecular weight. The second 

 agent is specially deutogenic; it is obtained from the fraction containing the 

 cell nuclei; its activity is distinctly reduced by hydrolysis; this is also essentially 

 a protein, but its action is probably influenced by the presence of nucleic acids. 

 The third agent is precipitable by streptomycine from the supernatant of high 

 speed centrifugation; this ribonucleoprotein induces a deutencephalon, but, if 

 warmed shortly, becomes acrogenic. More detailed information is expected in a 

 near future. 



From the standpoint of the morphologist, the novelty in these recent data is the 

 likelihood of dissociating the three organization levels included in notogenesis. 



