New York Agricultural Experiment Station. 183 



The work of Nencki and of Spiro^*^ has shown that phenylethyl- 

 amine can be formed from phenylalanine with separation of 

 carbon dioxide. 



Of these dififerent reactions furnisning carbon dioxide, we find 

 in the normal cheese under investigation evidence that tyrosine 

 has changed into oxyphenyethylamine and that the decomposi- 

 tion of arginine has resulted in the formation of its simpler pro- 

 ducts. We cannot say whether Nencki's reaction occurred, by 

 which phenylalanine was changed into phenylethylamine, since 

 we did not examine the cheese for these compounds. It is easily 

 conceivable that such a change may take place, since E. Fischer^*' 

 has shown the presence of phenylalanine among the cleavage 

 products of casein. There probably await discovery other simi- 

 lar reactions, now unknown, bearing on the formation of carbon 

 dioxide in proteolytic changes. ""' 



It appears to us that the carbon dioxide formed after the first 

 few weeks of ripening, in the case of the normal cheese, must 

 have come very largely from the decomposition of such com- 

 pounds as tyrosine and arginine. In the case of the different 

 normal cheddar cheeses that we have previously investigated, 

 the arginine and tyrosine commence to undergo proteolytic 

 change quite early in the ripening process. 



Reviewing briefly our discussion about the sources of carbon 

 dioxide in cheese, we. believe, from the evidence furnished, that 

 the carbon dioxide given off in the early age of the normal cheese 

 came largely from the decomposition of milk-sugar by lactic acid 

 organisms, while a small amount was probably due to the carbon 

 dioxide present in the milk and to the respiration of living organ- 

 isms present in the cheese. The carbon dioxide produced after 

 the first few weeks could apparently come only from the decom- 

 position of some compounds present in the cheese, among which 

 we were able to identify the change of tyrosine and arginine into 

 derived products with simultaneous formation of carbon dioxide. 



In the case of the chloroformed cheese, none of the carbon 

 dioxide could have come from the respiration of living cells or 



"^^ Beit, z. c/tem. Physiol, unci Pathol., 1 : 347 (1901). 

 "^^ Ztsch. Physiol. Che>n., 33: 151 (1901). 



