66 SCIENCE PROGRESS. 



tion with basic and neutral lead acetate, or mercuric nitrate, 

 but without success. 



Employing this method he showed that the whole of the 

 " residu fixe" consisted of amido-acids. These are of two 

 classes : — 



(A) In the first, which comprises over 80 per cent, of the 

 total weight, the ratio of N : O is equal to 1 : 2, and con- 

 sists of bodies of the following classes : — 



(i.) Amido-acids of the series C n H 2n+I N0 2 . These he 

 termed leucines. Of these were found Alanine 

 (C = 3) in small quantities only, Propalanine or 

 amido-butyric acid (C = 4), Butalanine or amido- 

 valeric acid (C = 5), both in considerable quan- 

 tities, and Leucine or amido-caproic acid (C = 6) 

 in very large quantities. It is to be noted that 

 glycocine (amido-acetic acid) was not found. 



(ii.) Amido-acids of the series C n H 2n _,N0 2 . These 

 belong to the acrylic acid series, and Schiitzen- 

 berger called them Leuceines. Here, too, the 

 term occurring most abundantly is (C = 6) "cap- 

 roic Leuceine," but bodies corresponding to 

 C = 5 or 4 were also found. 



(iii.) Amido-acids of the form C n H 2n N 2 4 or some 

 multiple of this. To these bodies he gave the 

 name of glucoproteins. The most abundant of 

 these are those in which C = 9 and C = 7 or 

 some multiple, but others where C = 11, 10, 8 

 have also been isolated. 



(B) In the second the ratio of N : O is 1 : 3 or 1 : 4 or 



2:5. It only contains about 16 per cent, of the total 

 weight. In this class are found : — 



(i.) Tyrosine C 9 H 1I N0 3 or oxyphenyl-amidopropionic 

 acid. The amount of this is about 3*5 per cent. 



(ii.) Nearly the same quantity of a body Tyroleucine 



C 7 H xx NO,. 



(iii.) Very small quantities of glutaminic acid C 5 H 9 NO r 

 This is an amido-acid (optically inactive) of one 

 of the pyrotartaric acids (glutaric). 

 Of these substances Schiitzenberger found varying 



