706 PHYSIOLOGY OF DIGESTION AND SECRETION. 



numerous products obtained by this complete hydrolysis consist 

 chiefly of amino-acids, that is, organic acids containing one or more 

 amido-groups (NH 2 ) in direct union with carbon. Some of these 

 bodies are monamino-acids, that is, contain one NH 2 group, such 

 as leucin, tyrosin, glycocoll, and include substances belonging to 

 the fatty acid series (aliphatic series), the benzene or carbocyclic 

 series, and the heterocyclic series, such as the pyrrol and the indol 

 group. Others are diamino-acids, containing two NH 2 groups. 

 These latter include lysin, histidin, and arginin, which, on account 

 of their basic properties, are frequently described as nitrogenous 

 bases, and sometimes as the hexon bases, since they contain six 

 carbon atoms. 



The chemical formulas for the best known of these bodies are as follows, 

 for their properties and chemical relationships reference must be made to 

 the text-books on organic chemistry: 



I. MONAMINO-BODIES. 

 FATTY ACID SERIES. 



Glycocoll or amido-acetic acid: CH 2 NH 2 COOH. This product is ob- 

 tained in especially large quantities by hydrolysis of gelatin. Accord- 

 ing to Abderhalden,* it is split off with difficulty by trypsin. 



Alanin or a-amidopropionic acid: CH 3 CHNH 2 COOH. 



Amidovalerianic acid: ^ 3 ^CHCHNH 2 COOH. 



Leucin or amidocaproic acid: Qg 3 ^CHCH 2 CHNH 2 COOH. As stated 



above, this compound was one of the first end-products of proteid 

 hydrolysis that was recognized. It may be obtained readily in 

 crystalline form. 



CHNH 2 COOH 

 Aspartic or amidosuccinic acid : 



CH 2 COOH. 

 Glutaminicacid: CH 2 /gH 2 COOH 



BENZENE OR AROMATIC SERIES. 



Tyrosin (para-oxyphenylamidopropionic acid) : C 6 H 4 OH . CH 2 . CHNH 2 - 

 COOH. This substance was also among the first recognized prod- 

 ucts of proteid hydrolysis It occurs early in the process of pan- 

 creatic digestion, and is easily obtained in crystalline form from 

 the digested mixture. It is especially interesting because of the 

 presence of a benzene nucleus, thus giving proof that the benzene 

 grouping occurs normally in the proteid molecule. 



Phenylalanin (phenylamidopropionic acid) : C 6 H 5 CH 2 CHNH 2 COOH. This 

 benzene derivative is, according to Abderhalden, split off from the 

 proteid with difficulty by the action of trypsin, although readily 

 produced by acid hydrolysis. 



PYRROL AND INDOL SERIES. 



CH CH 2 



! I 



a-Pyrrolidin carbonic acid : CH 2 CHCOOH. This substance, discovered 



\/ 

 NH 



* Abderhalden, " Zeitschrift f. physiol. Chemie," 44, 17, 1905. Consult 

 for general description of the digestion of proteids. 



