8 4 



Scientific Proceedings (73). 



soluble substances plus the ash is deducted from the total solids 

 of the meat and the result considered as representing protein 

 substance. Likewise this scheme falls short of an accurate 

 determination of the muscle proteins. Indeed even the total 

 nitrogenous substances cannot be thus obtained with precision, 

 for ether removes from meat various bodies containing nitrogen. 



The cause of these difficulties and uncertainty has been the 

 lack of an accurate analytical procedure for the direct deter- 

 mination of the proteins in muscle. It was however found 

 practicable to develop such a method, 1 an improved form of which 

 will appear elsewhere. The principle involved in the modified 

 procedure is coagulation of the muscle in alcohol and the removal 

 of the non-protein material by extraction. When this is carried 

 out with certain precautions it is possible to completely separate 

 the fatty and other non-protein material from the proteins, 

 which can be obtained in a high state of purity. 



The results thus arrived at by direct analysis are compared 

 in the following table to those obtained by calculation as above 

 indicated. The computed values exceed that of the protein 

 actually present, by fifteen to twenty per cent. In dietetic and 

 metabolic studies this discrepancy must therefore be considered. 

 A revision of various tables of food analyses in this respect is 

 indicated. 



Protein Content of Muscle. 



Species. 



Total Nitrogen 

 in Muscle. 



Protein Calcu- 

 lated (Total 

 N X 6 25). 



Protein Actually 

 Present. 



Nitrogen 5 in 

 Protein. 



Dog 



3-33 



20.8 



17.9 



16.3 



Rabbit 



3-39 



20.8 



16.7 



16.3 





3-43 



21.4 



17-5 



16.4 



Fish (halibut) 



310 



19.4 



16.7 



16.4 



1 Janney, N. W., and Csonka, F. A., Jour. Biol. Chem., 1915, XXII, 195. 



2 Not calculated ash free. 



