908 



APPENDIX. 



stituent of any animal tissue or secretion. It is, on the other hand, found normally 

 in plants, notably in beet-sugar molasses. It arises also as a constant product of 

 the action of alkalies and other reagents on both vegetable and animal proteids, and 

 of acids on gelatin. 1 It thus possesses considerable interest in respect of its re- 

 lation to the proteids. It crystallizes in rhombic prisms which are but sparingly 

 soluble in cold water or alcohol, readily soluble in boiling water. Its acid solutions 

 are dextro-rotatory, its alkaline Isevo-rotatory and reduce Fehling's fluid. It forms 

 a characteristic readily crystallizable compound with copper. Nitrous acid converts 

 it into malic acid. 



Glutaminic Acid. C 5 H 9 N0 4 . 



The circumstances and conditions under which this body occurs are in general 

 the same as for the aspartic acid, and hence as a product of proteid decomposition 

 it acquires some importance. It has not, however, as yet been obtained by the 

 action of pancreatic ferments on proteids, and in this it differs from the preceding 

 body. 



It crystallizes in rhombic tetrahedra or octahedra ; is not very soluble in cold, but 

 readily soluble in hot water ; insoluble in alcohol and ether. Its acid solutions 

 possess a strong dextro-rotatory power, and it reduces Fehling's fluid. 



Cystin. C 3 H 7 NS0 2 . 



Is the chief constituent of a rarely occurring urinary calculus in men and dogs. 

 It may also occur in renal concretions and in gravel, and is occasionally found in 

 urine. 



From calculi it is obtained, by extraction with ammonia, as colorless six-sided 

 tables or rhombohedra [Fig. 253], which are neutral and tasteless. It is insoluble 



in water, alcohol, and ether, soluble in ammonia and the other alkalies, and also in 

 mineral acids. The fact that this body is one of the few oystalline substances, 

 occurring physiologically, which contain sulphur, renders its detection very easy. 

 Apart from its insolubility in water, etc. , it yields, with caustic potash and salts of 

 either silver or lead, a brown coloration due to the presence of the sulphides of 

 these metals. 



According to Dewar and Gamgee, 2 cystin is amido-sulpho-pyruvic acid, and its formula is 

 C 3 H 5 NSO 2 pyruvic being lactic acid minus two atoms of hydrogen. 



1 Horbaczewski, Sitzb d. k. Akad. d. Wiss., Wien, 1880. 2 Abth., Juni Heft, 



2 Journ. of Anat. and Physiol., Nov., 1870, p. 143. 



