828 APPENDIX. 



primary constituents of cells, especially in spermat-o/oa. In this group 

 are argenim, lysin., and hystidtn. 



Amides. These are bodies of the ammonia type (NH S ) in which one 

 or more of the H atoms are replaced by organic acid residues (an acid 

 residue = the acid minus hydroxyl ; e-y., CH CO is the residue of 

 ( 1 H 3 COOH). Monacetamide = NH,, OH 3 CO There are also more 

 complicated amides which are built up from two molecules of ammonia; 

 < J .(/., urea or carbamide, which is formed from carbonic acid and is usu- 

 ally written CO, NH 2 , NH 2 . 



Amido-acids. These are bodies of the ammonia type (NH 3 ) in which 

 one or more of the H atoms of the ammonia are replaced by organic acid 

 radicles; they may also be regarded as acids in which one or more of the 

 H atoms of the acid radicle are replaced by amidogen, NH 2 . As the 

 term implies that they are acids, it is necessary that they contain the 

 carboxyl group (COOH) intact. For example, glycin (amido-acetic acid) 

 i- either NH 2 , CH, COOH or CH 2 (NH t ), COOH. 



Nitrogenous or Nuclein Bases. The members of this group are very 

 closely related and consist of hypoxanthin (C 6 H 4 N 4 0), xanthin 

 (C 5 H 4 N 4 O 2 ), adenin (C S H 5 ]S T 5 ), and guanin (C 5 H 5 N 5 0). Besides occur- 

 ring in ordinary proteid decomposition, they are also always present in 

 all downward chemical changes in the cells. Uric acid (C 5 H 4 N 4 3 ), 

 though not a member of the group, is shown to be closely related by 

 studying their chemical composition. By oxidation uric acid yields urea 

 and alloxan (C 4 H 2 N 2 O 4 ); it has been found that in alloxan there is pres- 

 ent a radicle C 5 N 4 known as the purin or alloxan-uric nucleus ; purin is 

 formed from this radicle by the substitution of H atoms. Both uric acid 

 and the nuclein bases can be derived from this base ; hypoxanthin is oxy- 

 purin, uric acid is tri-oxypurin, adenin is amino-oxypurin, etc. 



Protargons. These are very complex phosphorus-containing bodies 

 which are chiefly obtained from nervous tissues. Protargon was at one 

 time considered an entity, but, according to the most recent views, it is 

 merely a mixture of cerebrin and lecithin. 



Of the bodies which constitute the above-mentioned groups, only the 

 following need be described : 



Glycin, Glycocol. Glycocin, or ) p w ^r^x _ / p-rr ^NH \ 

 Amido-acetic acid. f C * H * lN H * < CO OH J 



This substance occurs in the body in combination as in the biliary 

 acids, but is never free. Glycocholic acid, when treated with weak acids, 

 with alkalies, or with baryta water, splits up into cholic acid and glycin, 

 or amido-acetic acid. Thus : C 26 H 13 N0 6 + H 2 = C 2fi H 40 O 6 + C 2 H 5 K0 2 . 

 Glycocholic acid -|- water = cholic acid -{- glycin, and under similar 

 circumstances Taurocholic acid splits up into cholic acid and taurin : 



