ADDITIONS AND NOTES TO VOL. I. 471 



bodies of an infusorium, Euylena viridis. These animalcules 

 after being freed as much as possible from other infusoria, were 

 first treated with ether and spirit, and then with a boiling mixture 

 of spirit and hydrochloric acid in order to remove the colour ; the 

 residue was mixed with water and thrown upon a cotton filter 

 which allowed the granules of paramylon to pass, but retained the 

 investing membranes of the animals. The substance was purified 

 by solution in potash-ley, and precipitation with hydrochloric acid. 



CELLULOSE. C 12 H 10 O 10 . 



Properties. In its purest state this substance forms a spongy 

 mass insoluble in all neutral menstrua., but very slightly soluble in 

 alkaline solutions ; it is convertible into dextrin both by sulphuric 

 acid and by diastase. 



If cellulose be treated with a mixture of four parts of concen- 

 trated sulphuric acid and one part of water, it swells on trituration 

 into a clear jelly which at first is stiff but gradually becomes quite 

 fluid : on the addition of water or alcohol there is a deposition of 

 white flakes which are insoluble in hot water, alcohol, and ether, 

 but possess the remarkable property of being coloured blue by 

 iodine like starch ; they differ, however, essentially from starch in 

 this respect, that the iodine may be washed out with water and the 

 blue colour destroyed, which is not the case with starch. This pro- 

 duct of the metamorphosis of cellulose has hence been named amy- 

 loid; its composition has been found to correspond with the formula, 

 C 48 H 41 O 41 . This substance is readily soluble in sulphuric acid, 

 from which it may be again precipitated unchanged by water : it 

 dissolves in strong nitric acid, without any development of gas ; but 

 on boiling there is a formation of oxalic acid : it only dissolves with 

 difficulty in hydrochloric acid, from which it is not precipitated by 

 ammonia ; moreover, ammonia does riot dissolve it. It swells in a 

 strong solution of potash, and dissolves on the addition of water, 

 from which it may be again thrown down by acetic acid. By 

 the prolonged action of alkalies, cellulose is converted into a sub- 

 stance to which iodine communicates a dark violet, or almost black 

 colour. Rotten potatoes contain a ferment which dissolves and 

 destroys the cellulose, but in no way affects the starch. 



The formation of this substance, and its reaction towards iodine, 

 have been employed for the recognition of cellulose. 



If, for instance, vegetable tissues, consisting of cellulose, be 

 moistened with sulphuric acid and tincture of iodine, they assume 

 a beautiful blue colour, which, however, gradually disappears on 

 the addition of water. Moreover, chloride of zinc converts cellu- 



