446 GERMINAL ORGANIZATION INDUCTION PHENOMENA 4 



or chemical means. Yet, in two cases, a biological treatment apparently realizes 

 such a reverse transformation in the guinea-pig liver, which is known as typically 

 acrogenic after the ordinary treatment with ethanol. A sufficient starvation of 

 the donor causes its liver to become notogenic (Vahs, 1957a) a modification 

 thus related to a longrun change in the liver cells. A more rapid reverse takes place 

 when a piece of liver (from a well-fed animal) is preserved overnight at 4° C in 

 organo-specific rabbit antiserum to be treated 3 h. at + 4°C in ethanol, and 

 finally carefully rinsed. A distinct modification of the inductive action is then 

 observed in comparison with pieces treated with normal rabbit serum (Vainio, 

 1958). Both kind of pieces, indeed, become more notogenic than when used with- 

 out any previous sejourn in rabbit serum, but the shift to notogenesis, perceptible 

 by the higher frequency of fin, pronephros, myotomes, notochord, is more 

 marked after the antiserum treatment. Parallel experiments with bone marrow 

 of the same donors only reveal a reduction of the notogenic effect, and this is 

 also partly true for kidney. The author is of the opinion that these results are due to 

 an adsorption by the liver of a notogenic agent present in the rabbit serum^ and 

 apparently more abundant in the antiserum. 



It is not necessary to insist that these two exceptions to the ordinary conversion 

 are obtained in complex conditions and do not mean that the acrogenic agent is 

 effectively transformed into the notogenic one. Thus, one is not bound to consider 

 that the transformation is possible both ways. 



For the regular shifting from noto- to acrogenesis, it is of course difficult to 

 exclude the interpretation that the latter agent is present beforehand, but in- 

 hibited by the former one, which has simply to be eliminated by some procedure, 

 in order to obtain the opposite effect. Toivonen and his group, as well as Englander 

 and Johnen (1957) and Vahs (1957a), are favorable to this interpretation. Their 

 thesis is newly supported by two accurate investigations. Kuusi (1957) has pro- 

 ceeded to fractionation of the guinea-pig bone marrow and compared the in- 

 ductive capacity of the various parts. The notogenic — the author speaks of 

 mesoderm inductor — component is predominent, but there is some weak acrogenic 

 action, which the author calls neural. Preserving the bone marrow in ethanol for 

 seven months, in a refrigerator, practically eliminates all notogenic reaction. 

 Fractionation in butanol completely suppresses the same agent, both in the 

 soluble fraction and in the tissue residue; some acrogenic reactions, especially 

 sensory placodes, are maintained. Saline extraction works in the same direction^. 

 For several reasons, none of which appears as really cogent, Kuusi considers that 

 "the mesodermal and neural inductors are more or less independent of each 

 other". She adds: "Since these two different types of inactivation exist", — an 

 allusion to the effects of brief heating and of ethanol treatment — "it seems 

 improbable that the mesoderm inductor is transformed into neural inductor". 

 Pentinen, Saxen, Toivonen and Vainio (1958) have described a new method 

 for changing the inducing properties of cviltivated cells. HeLa cells are cultivated 



^ The existence of inducing factors in blood has been confirmed by Vainio, Toivonen and 

 Saxen (1958). 



^ The same paper mentions that the spleen is also definitely notogenic, the white and red 

 pulps acting the same way ; this organ is, like bone-marrow, a strict derivate of the mesoderm. 



