CHEMICAL BASIS OF THE ANIMAL BODY. 153 



glutamic acid. It is also now recognised as a product in minute 

 quantities of the pancreatic digestion of fibrin 1 and vegetable glutin 2 , 

 although it does not occur as a constituent of any animal tissue or 

 secretion. 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, laevo- 

 rotatory. It forms a characteristic readily crystallisable compound 

 with oxide of copper, which is practically 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 . 



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

 tartaric acid.) 



This acid is homologous with aspartic acid. The circumstances 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 

 decomposition of proteids it acquires some considerable importance. It 

 is always prepared by treating proteids with boiling mineral acids 4 . 



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 dextro- 

 rotatory power. 



4. Asparagin. C 4 H 8 N 2 3 + H 2 0. [COOH . CH 2 . CH (NH 2 ) . 

 CONHJ. Amido-succinamic acid. 



Although asparagin 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 undoubtedly 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 (leucin, glycin &c.) to give rise to urea when 

 taken into the body of carnivora 5 , and to uric acid in that of birds 6 . 



1 Kadziszewski u. Salkowski, Ber. d. deutsch. chem. Gesell Jahrg. vn. (1874), 

 S. 1050. 



2 v. Knieriem, Zeitsch. f. BioL Bd. xi. (1875), S. 198. 



3 Hofmeister, Sitzb. d. k. Akad. d. Wiss. Wien, Bd. LXXV. (1877), 2 Abth. 

 Marz-Hft. 



4 Ritthausen u. Kreusler, Jn.f.prakt. Chem. (2) Bd. in. (1871), S. 314 



5 v. Knieriem, Zt. f. BioL Bd. x. (1874), S. 277. 



6 v. Knieriem, Ibid. xin. (1877), S. 36. 



