132 H. R. Mahler, H. Walter, A. Bulbenko and D. W. Allmann 



We have shown that the organ-specific locahzation phenomenon, previously 

 observed with chorio-allantoic transplants, can be dupHcated by the injection 

 of homogenates of aduh tissue. Similarly Tumanishvili et al. (35) found almost 

 simultaneously that host organ enlargement could also be elicited by the same 

 technique. This demonstration of the essential similarity of two approaches 

 clears the way for an investigation of the problem by means of relatively 

 straightforward biochemical and enzymological techniques rather than the 

 more demanding ones of experimental embryology. Obviously only a bare 

 beginning has been made. The findings will have to be confiiTned and extended 

 and several relatively trivial explanations excluded. Among such explanations 

 are, for instance, the transfer of whole cells on the one hand, and differential 

 composition and/or incorporation rates with respect to cystine and methionine 

 in the two tissues studied, on the other. Ebert claims to have eliminated both 

 these alternatives in his transplantation experiments; in the light of the available 

 information, they are not very likely in the present case. Nevertheless they 

 will have to be rigorously excluded. Our tentative interpretation of the prelimi- 

 nary results described is identical with that advanced by Ebert: that we are 

 dealing with a specific transfer of rather large units from the donor preparation 

 to the embryonic organ. 



Preliminary experiments indicate that the injection of either heart or liver 

 (donor) homogenates leads to an increase in specific activity in the liver as 

 compared to the heart. The effect in this case is therefore non-specific and 

 possibly related to the higher mitotic and synthetic activity of liver relative 

 to heart, i.e. to fuller differentiation. Another line of approach which promises 

 to be of some interest is to determine the cell fraction or fractions, if any, 

 responsible for eliciting the effect both with respect to the donor and the acceptor 

 organ. Impetus is added to this approach by the recent experiments which 

 have focussed attention on the soluble and microsomal fractions as being 

 involved in the initial phases of protein synthesis. In preliminary experiments 

 with fractionated, dialysed heart homogenates the data of Table VI were 



Table VI. Transfer of Label from Donor Heart 

 Fractions into Organs of Recipient Embryos 



obtained. The number of data in each row corresponds to the number of 

 experiments actually performed. Thus the results for the microsomal and 

 mitochondrial fractions must be regarded as exceedingly tentative. With this 

 proviso, components of the soluble fraction of the cytoplasm might be regarded 

 as responsible for the phenomenon observed with whole heart homogenates. 



