432 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Vor VIII 
Leucine or 4-amino-isobutylacetic acid, 
(Ris 
Ci» CH. CH, CH(Mia,). COOH; 
Arginine, or 6-guanidin-c-amino-valerianic acid, 
NE; iy NH, 
| | 
NH=C—NH CH, CH.,. (CH, CH. COOH, 
Histidine, or -imidoazol-a-amino-propionic acid, 
Lysine or a-¢ diamino-caproic acid, 
NH, NH, 
| | 
CH. CHECH. CH. He GOGH 
The presence of these and other amino-acids in the protein mole- 
cule is highly significant. If we regard the molecule as a building or 
edifice then these amino-acids are the building stones and the character 
of the molecule must depend on the amino groups which constitute it 
just as the character of the building depends on the building material 
used. 
The occurrence of methyl groups places the relation of the proteins 
to the fats and carbohydrates in a very clear light. It indicates that 
after all the distinction between proteins on the one hand and fats and 
carbohydrates on the other is not a radical one and that the framework 
of the molecules in all three classes of compounds is fundamentally the 
same, namely, a chain of alkyl radicles arranged in series and groups 
more or less individualized in the chain. The highest number of alkyl 
radicles in a single group is that found in diamino-trioxy-dodecanic 
acid, C,.H,,;N.O,, of which there are small quantities found in certain of 
the proteins but the most common groups are those which have less 
than six alkyl radicles. 
