188 Uric Acid Crystals from Astacus fluviatilis. [Mar. 5, 



is obtained. This murexide so obtained crystallises in prisms, which 

 by reflected light exhibit a splendid green metallic lustre, and by 

 transmitted light are a deep reddish-purple. 



On running in a solution of potassium hydrate upon a microscopic 

 slide containing some of these murexide crystals they were dissolved. 

 From these reactions it is evident that these rhombic crystals are 

 deposits of uric acid (C 5 H 4 N 4 3 ) from the secretion of the green 

 gland of the crayfish. 



On examining the uric acid crystals (deposited from the secretion 

 by means of alcohol) under the microscope, they are seen to be 

 covered more or less with a very thin and superficial coating of some 

 brown colouring matter, probably some pigment. 



But, beyond this discovery of uric acid in the secretion of the 

 green gland of Astacus fluviatilis, I have found that on treating the 

 secretion with boiling hydrochloric acid a solution was obtained 

 containing in suspension flaky uric acid which was filtered off, and 

 on allowing the filtrate to cool a few crystals (guanin hydrochlorate) 

 separate which are soluble in hot water, and on the addition of 

 ammonia to this hot aqueous solution a precipitate is obtained of 

 guanin (C 5 HVN" 5 0), the precipitated guanin being made up of num- 

 bers of minute microscopic crystals. On running in warm dilute 

 nitric acid (upon the slide) these crystals disappeared, but were 

 precipitated again on adding a drop of silver nitrate in the form of 

 the nitrate of silver compound (C 5 H 5 N 5 0,AgN0 3 ) of guanin. 



I think this investigation proves that this so-called green gland of 

 Astacus fluviatilis is a true urinary organ, its secretion containing uric 

 acid and very small traces of the base guanin : the green gland is, 

 therefore, physiologically the kidney of the animal. 



II. " On the Atomic Weight of Glucinum (Beryllium). Second 

 Paper." By T. S. Humpidge, Ph.D., B.Sc, Professor of 

 Chemistry in the University College of Wales, Aberyst- 

 wyth. Communicated by Prof. E. Frankland, F.R.S. 

 Received February 27, 1885. 



(Abstract.) 



This paper is a continuation of one previously communicated to 

 the Royal Society.* The author has prepared a sample of metallic 

 glucinum, having the composition — 



* " Proc. Roy. Soc," vol. 35, p. 137. 



