82 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



cent. Fish muscle contains the least amount of glutamic acid ; the 

 amounts in the other muscles are very close. The muscles are alike in 

 respect of tyrosine, aspartic acid, arginine, lysine and histidine, and 

 also phenylalanine, which is slightly more abundant in scallop muscle. 

 Glycine is present in considerable amount in the free state in scallop 

 muscle ; otherwise, it is present only in ox muscle to any extent ; 

 since syntonin contains very little glycine, it is probably derived from 

 the connective tissue in the ox muscle. It is curious that, as we 

 pass from the lower forms of life to the higher, the amounts of glycine, 

 alanine, leucine and proline increase. 



The amount of protein in the nervous system seems to be small, as 

 the total quantity of amino acid isolated by Abderhalden and Weil 

 [1912, 2 ; 1913, i] does not exceed 10 per cent. Mention may again 

 be made of the presence of norleucine amongst these amino acids. 



The crystalline protein from the juice ofAntiaris toxicaria examined 

 by Kotake and Knoop [1911] is a remarkable protein probably a 

 complex polypeptide with icr6 per cent, of cystine. Further data 

 will no doubt decide the nature of this protein. Only a small quantity 

 of material has been so far available. 



Derivatives of Proteins. 



Complete analyses of the proteoses products intermediate between 

 the proteins and amino acids have been undertaken by Levene, and 

 by Levene in conjunction with Van Slyke and Birchard, and by Skraup 

 and his pupils. 



In the case of the gelatoses and gelatin peptone, Levene [1902-3, 

 1904] found that the gelatoses contained 17-20 per cent, of glycine 

 and gelatin peptone 17-4 per cent, as compared with 16-5 per cent, in 

 gelatin itself. Skraup and Hummelberger [1908] gave the composition 

 of gelatoses precipitated by half, two-thirds and complete saturation 

 with ammonium sulphate and of gelatin peptone as follows : 



The gelatoses contain more glycine than gelatin which contains 

 9 f 6 per cent, but the peptone less. Levene found that amino acids 



