282 F. CEDRANGOLO 



Earth when the atmosphere was constituted by methane, ammonia, water, and 

 hydrogen. This hypothesis was accepted and followed successively by famous 

 scientists like Urey and Bernai and was recently (1953) submitted to rigid 

 experimental control by Stanley L. Miller [5]* in the Chemical Laboratory of 

 the University of Chicago in the United States of America. Miller has constructed 

 a special apparatus in which for a longest period of time (one week) was produced 

 an electric discharge in an atmosphere constituted precisely by aqueous vapour, 

 hydrogen, methane, and ammonia. The water circulates continuously in changing 

 states from the liquid state in the boiling flask to the gaseous state in corre- 

 spondence to the electrodes and then again for condensation in the liquid state 

 in the flask. It was observed that, from the first day, the water was light yellow 

 in colour and then turned decidedly to dark red at the end of a week. It was 

 evident that the colour depended upon some organic compounds formed during 

 the experiments: these compounds anyway were submitted to a very precise 

 chemical analysis and were identified as amino acids. Among the recognized 

 amino acids are glycine, a- and /3-alanine, with large probability also aspartic 

 acid and a-aminobutyric acid. From this model experiment, it is reasonable 

 therefore to conclude [7, 8] that also on Earth at a certain period (exactly when 

 its atmosphere was constituted by hydrogen, water, ammonia, and methane and 

 not by oxygen, nitrogen, water, and carbon dioxide as presently) there was the 

 possibility of the appearance of amino acids. Considering the probable existence 

 in this primitive atmosphere also of hydrocarbons different from and more com- 

 plex than methane, and considering also that surely the natural electric discharge 

 must have had a greater energy than that employed in the Aliller apparatus, 

 anyone can think that in that time very numerous amino acids formed and also 

 that this formation must have occurred in large quantities. 



From the appearance of the amino acids on Earth until their organization in 

 the molecules of one protid the way does not seem, at least from the theoretical 

 point of view, too long, even if it is not now possible to give a satisfactory and 

 conclusive solution to this problem. However, it is necessary to think that the 

 process through which many hundreds of amino acids are combined to build a 

 protein molecule is an endoergonic process and that the energy necessary must 

 have been furnished either as electric energy or as another type (thermic, radiant 

 energy produced in the dissimilation of organic compounds). We do not know 

 yet how the long protein chains grow as we do not know how the same long 

 chain of nucleic acids grow [9]. It is possible that the amino acids must have been 

 phosphorylated by adenosine triphosphate before being included in the proteins. 

 We have good reason to believe that the giant molecules of nucleic acids play a 



* We believe that the experiment of Miller is in need of rapid confirmation considering 

 its importance and also, from another point of view, because according to Roka [6] 

 'ob dieser Versuch allerdings schlüssig ist, wird angezweifelt'. According to Roka {op. 

 cit.) 'nach mündlicher Mitteilung von K. Felix soll H. C. Urey, in dessen Institut das 

 Experiment ausgeführt wurde, anzweifeln, ob Verunreinigungen mit Bakterien aus- 

 geschlossen waren'. If the experiment is not reproducible, the appearance of amino acids 

 on Earth and their formation from the components of the primitive atmosphere would 

 be again subject of new discussion and new hypothesis, which would be valid only if 

 supported by positive results of new experiments. 



