CHEMICAL BASIS OF THE ANIMAL BODY. 1258 



pancreatic digestion of fibrin and vegetable gluten, although it 

 does not occur as a constituent of any animal tissue or secre- 

 tion. It crystallizes in rhombic prisms which are but sparingly 

 soluble in cold water or alcohol, but readily soluble in boiling 

 water. Its solutions, if strongly acid, are dextrorotatory, but 

 if alkaline, lsevorotatory. It forms a characteristic readily 

 crystallizable compound with oxide of copper, which is prac- 

 tically insoluble in cold, but soluble in boiling water, and may 

 be used for the separation of aspartic acid from solutions in 

 which it is mixed with other substances. 



3. Glutamic (or glutaminui) acid. C 5 H 9 N0 4 . (Amido- 

 pyrotartaric acid.) 



This acid is homologous with aspartic acid. The circum- 

 stances and conditions under which it occurs are in general 

 the same as for aspartic acid, but it has not as yet been 

 obtained by the action of pancreatic enzymes on proteids and 

 is never found in any animal tissues or - secretions. But as a 

 product, often to a large amount, of the artificial decomposi- 

 tion of proteids it acquires some considerable importance. It 

 is always prepared by treating proteids with boiling mineral 

 acids. 



It crystallizes in rhombic tetrahedra or octahedra ; is not 

 very soluble in cold, but readily soluble in hot water ; insoluble 

 in alcohol and in ether. Its aqueous and acid solutions possess 

 a strong dextrorotatory power. 



4. Asparagine. C^Hg^Og + H 2 0. [COOH . CH 2 . CH 

 (NH 2 ).C(_)NH 2 ]. (Amido-succinamic acid.) 



Although asparagine is not found as a constituent of the 

 animal body it is a substance of considerable interest to the 

 physiologist. Not only is it closely related to aspartic acid, 

 into which it may be converted by the action of boiling acids 

 and alkalis, yielding at the same time ammonia, but it undoubt- 

 edly plays a most important part in the constructive proteid 

 metabolism of plants. Further, it exists in not inconsiderable 

 amount in many plant-tissues used as food by man, and is 

 known, like so many of the members of the numerous class of 

 amido-acids to which it belongs (leucine, glycine, etc.), to give 

 rise to urea when taken into the body of carnivora, and to uric 

 acid in that of birds. 



Asparagine crystallizes readily in large rhombic prisms 

 which are not very soluble in cold, but readily soluble in hot 

 water, and are insoluble in absolute alcohol and in ether. Its 

 solutions are dextrorotatory. It may be prepared synthetically, 

 but is usually obtained by crystallization from the expressed 

 juice or extracts of the seedlings of peas, beans or lupins. 



