342 CARNEGIE INSTITUTION OF WASHINGTON. 



Dr. Chibnall has devoted himself to completing work begun in England and 

 has furthermore demonstrated the possibility of obtaining the contents of 

 the vacuole of the cells of the spinach-leaf uncontaminated with the proto- 

 plasmic constituents. Since this process can be applied on a large scale, it 

 should be possible to learn far more about the chemical make-up of the 

 constituents of the vacuole than we now know. It appears possible, also, 

 after the contents of the vacuole have been removed, to extract the proto- 

 plasm as a colloidal solution fit for chemical examination. Dr. Chibnall 

 expects to continue these investigations during the coming year. 



During the past year Dr. Vickery has continued his study of the rate of 

 hydrolysis of gliadin and has directed his attention especially to an insoluble 

 product which separates from the solution during this process. This product 

 might be either a resistant fraction, which for many years chemists have con- 

 sidered to be characteristic of the protein molecule, or it might be gliadin from 

 which only the amide nitrogen had been eliminated. A comparison of curves 

 showing the rate of hydrolysis of this product and that of gliadin revealed no 

 marked differences, thus demonstrating that gliadin, at least, does not contain 

 a resistant moiety. 



With respect to its content of arginine, lysine, and the non-amino nitrogen 

 of the filtrate from the basic amino acids, which is probably very largely 

 proline nitrogen, the insoluble product differs in constitution from that cal- 

 culated for gliadin from which amide nitrogen alone has been removed. 

 Moreover, when prepared under the conditions detailed above, this insoluble 

 fraction contains all the lysine of the original gliadin. In its production, there- 

 fore, hydrolysis of peptide bindings as well as of amide bindings has played a 

 part. Efforts to remove only amide nitrogen from gliadin, without simul- 

 taneously rupturing peptide bonds, have been unsuccessful. 



In connection with all studies on the role of protein as a component of the 

 dietary it has become desirable to prepare rations in which the protein under 

 consideration shall form as far as possible the sole source of nitrogen in the 

 dietary. In the past the fact that the commonly used sources of vitamine B 

 contain more or less nitrogenous material, some of which is protein, has led to 

 more or less justifiable criticism of such studies. The vitamine component 

 thus introduces an added variable into the experiment so far as the protein 

 factors are concerned. It was a helpful step in the direction of progress when 

 it became possible to use, as a source of vitamine B, a fraction of yeast extract 

 which no longer gives the ordinary tests for proteins. We have accordingly 

 found it highly advantageous to make use of this "concentrate" in our newer 

 studies. Before engaging in any extensive use of the concentrate we have 

 made an investigation of the relation of the size of the animal at different 

 stages of development to the quantity of the yeast fraction required to secure 

 satisfactory growth on diets of the same composition. Recently we reported 

 similar experiments with dried whole yeast as a source of vitamine B for rats. 

 Although the absolute quantity of dried yeast required increased with the 

 augmented size of the animal, it appeared that the daily requisite per 100 

 grams of body-weight approximated what is contained in 50 to 60 mg. of the 

 dried yeast used by us. 



The experiments with the yeast concentrate first prepared by Osborne and 

 Wakeman and described in earlier reports are in progress. They already 

 indicate that as the body increases in size larger absolute amounts of the 



