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



values. Those for the egg white are only a small fraction of those expected, 

 while those for the yolk are uniformly about two-fold greater. It is thus 

 apparent that at least one of the assumptions cited cannot be valid. The 

 simplest modification would be to postulate that assumption (b) is not true, 

 and that over the time-period studied egg white proteins are not precursors 



Table II. Amounts of Embryonic Protein Formed Compared 

 to that Calculated from Tracer Data 



* From injected albumin tracer. 



of embryonic proteins. Soluble proteins injected into the yolk can be utilized 

 for this purpose, and may be more efficient than some of the yolk proteins 

 proper. 



3. Is There Evidence for Selective Utilization of Amino Acids, Peptides or Proteins ? 



In the next series of experiments we compared serum albumin, albumin 

 peptides and amino acids all injected into the yolk, with the same precursors 

 injected into egg white. The design of the experiment was the same as before 

 and the results of one run are summarized in Table III, 



Table III. Incorporation of Protein Precursors into Chick Embryos* 



Day 



after 



Precursors injected into 



YOLK 



Precursors injected into 

 egg-white 



* Expressed as per cent of injected activity recovered per embryo. 



We see that except for albumin injected into egg-white, which has already 

 been discussed, all the precursors tested appear to be utilized with approxi- 

 mately equal efficiency regardless of whether they are injected into the yolk 

 or the egg white. This is not limited to serum albumin, but holds true equally 

 well for serum globulin and ovalbumin and their peptides as is shown in Table IV. 



