REVERSION OF HYDROLYSIS 



435 



Additional experiments were undertaken by myself and Biddle 

 (55) with a view to further elucidating the relationship between 

 the paranucleins and the synthetic substances which I have 

 described. We determined their carbon, hydrogen and nitrogen 

 content, with the results tabulated below*; for the purpose of 

 comparison analyses of paranuclein by Lubavin (41) are also 

 included in the table. 



* Three separate preparations of this substance were made, the figures given (except that for N 

 which was only determined in the first preparation) are those obtained with the preparation which 

 had been subjected to the most rigorous purification. 



It is evident that the carbon, hydrogen, and nitrogen-contents 

 of paranuclein, paranuclein A and the substance synthesized 

 at 70 degrees, are so closely similar that they may be considered 

 identical; they also agree well with the original analyses of 

 Lubavin. The product obtained at 36 degrees, however, con- 

 tains a very appreciably higher percentage of carbon. Since the 

 carbon-content of this preparation was found to sink somewhat 

 during successive purifications it appears possible that the high 

 carbon is due to contamination with some impurity, possibly a 

 coagulose (Cf. below). The product which is formed at 36 

 degrees is deposited from the mixture more slowly than that 

 which is formed at 70 degrees, hence it would be more liable to 

 carry down contaminations. 



The objection has been urged by Bayliss (5) and by Rohonyi 

 (57) that it is impossible to adequately identify a protein by 

 purely analytical similarities. They point out that Gruebler's 

 pepsin contains a substance which is coagulable by heating and 

 that after this substance has been removed the pepsin solution 

 no longer retains the power of causing the appearance of a pre- 

 cipitate when mixed with a solution of the products of the peptic 

 hydrolysis of casein. Merck's pepsin, on the other hand, yields 



* For quantitive details of the methods employed in preparing these sub- 

 stances in bulk consult the communication just cited. 



