124 ANIMAL CHEMISTRY LECTURE T. 



from water and ammonia, we have the following alcoholic deriva- 

 tives : 



Hydrates Amines 



^ I Hydric H H 1 ^ 



^ I Methylic C H 3 H } N Methyl-ainin 



Ethylic N Ethyl-amine 



Now, replacing an atom of hydrogen or the atom of chlorine, 

 in acetic and chloracetic acid respectively, by the residue of water, 

 HO, we obtain glycolic or oxiacetic acid ; replacing it by the resi- 

 due of ammonia, HHN, we obtain amid-acetic acid, or glycocine; 

 replacing it by the residue of methylamine, CH 3 HN, we obtain 

 methyl-amid- acetic acid, or methyl-glycocine, or sarcosine; and, 

 lastly, replacing it by the residue of ethylamiue, C 2 H 5 HN, we 

 obtain ethyl-amid-acetic acid, or ethyl-glycocine, thus: 



Acetic Derivatives 



C 2 H 4 2 Acetic acid 



C 2 H 3 2 (C1) Chlor-acetic acid 



C 2 H 3 2 (HO) Glycolic acid 



C 2 H 3 2 (H 2 N) Glycocine 



CJE 3 2 (C H 4 N) Sarcosine or methyl-glycocine . 



C a H 3 2 (C 2 H 6 N) Ethyl-glycocine 



The constitution and mutual relationship of the above tabulated 

 bodies have been established as well by their recomposition as 

 by their decomposition. In the case of tyrosine, however, we 

 have only a knowledge of its decompositions to fall back upon, 

 from which, however, it would appear, according to Schmitt and 

 Nasse, that it corresponds most nearly in constitution with sarco- 

 sine or methyl-glycocine among natural products, and still more 

 nearly with the artificial ethyl-glycocine of Heintz. Just, indeed, 

 as sarcosine is acetic acid in which an atom of hydrogen is replaced 

 by the residue of methylamine, so is tyrosine salicic acid in which 

 an atom of hydrogen is replaced by the residue of ethylamine, 

 thus: 



