Metastable Solutions of Inorganic Colloids. 



17 



There is some evidence suggesting the possibility that chlorophyll may be 

 built up not only from ethyl chlorophyllide and phytyl alcohol, but also from 

 xanthophyll and the products of the photo-oxidation of chlorophyll. The 

 assimilation of carbon dioxide involves a complex series of chemical 

 changes which are reversible in part at least, in which chlorophyll and 

 xanthophyll play a direct chemical part, and in which light acts as an 

 accelerating and possibly as a directive agency. 



On Forms of Growth Resembling Living Organisms and their 

 Products Slowly Deposited from Metastable Sohuions of 

 Inorganic Colloids. 

 By Prof. Benjamln Moore, M.A., D.Sc, F.E.S., and W. G. Evans, B.Sc. 



(Received February 6, 1915.) 



(From the Biochemical Laboratory, University of Liverpool.) 

 [Plate 1.] 



Graham, in his classical papers on colloids, draws attention to the remark- 

 able dynamic properties possessed by matter in the colloidal form, whether 

 as a hydrosol or a hydrogel. He states that " another and eminently 

 characteristic quality of colloids is their mutability. Their existence is a 

 continued metastasis. A colloid may be compared in this respect to water, 

 while existing liquid at a temperature under its usual freezing point, or to a 

 supersaturated saline solution. The colloidal is, in fact, a dynamical state of 

 matter ; the crystalloidal being the statical condition. The colloid possesses 

 energia. It may be looked upon as the probable primary source of the force 

 appearing in the phenomena of vitality. To the gradual manner in which 

 colloidal changes take place (for they always demand time as an element), 

 may the characteristic protraction of chemico-organic changes also be 

 referred."* 



It is only within recent years that the importance of these slow metastable 

 variations in colloids so closely simulating the changes in living organisms, 

 which are themselves metastable colloidal complexes, have been appreciated 

 by a few authors, as thus clearly expressed by Graham over 50 years ago. 



A metastable colloidal solution is, as Graham states, comparable to a 



* 'Phil. Trans.,' vol. 151, pp. 183-224 (1861). 

 VOL. LXXXIX. — B. C 



