I.— PHYSIOLOGY. iG7 



additional mechanism whereby the synthesised product is removed from the 

 sphere of action, for if it diffused off the surface again it would be subject 

 to the equilibrium conditions which are present in the solution. It may 

 be that the arrangements in the cell are such that only small amounts of the 

 substrate are dealt with at a time so that complete synthesis is achieved 

 and the synthetic product removed. This implies that the synthetic 

 activity takes place in cycles due possibly to cyclic changes in the activity 

 of the active surface or to a mechanism whereby only as much substrate 

 for the synthesis is admitted to the sphere of action as can be dealt with 

 without saturating the active surface. It is difficult to translate experi- 

 ments such as those described by Freundlich to explain synthesis in the 

 living cell without additional mechanisms such as these. 



We have also to consider how the synthetic product is dealt with in 

 the cell so as to protect it from the disruptive agencies which exist there. 

 Arrangements for this purpose must be present since we know that sub- 

 stances may accumulate in cells which contain enzymes that hydrolyse 

 them. For example, fat and lipase co-exist in the liver cell and also glyco- 

 gen and amylase. The phenomena of autolysis illustrate this same fact 

 too. Whatever these arrangements are they appear in certain instances 

 to be closely associated with the life of the cell, for after death they cease 

 to operate and the synthetic product is again broken down. However 

 difficult it is to form a conception of them it may be necessary to do so 

 since they must form a part of any system which is put forward to explain 

 synthesis as a result of the intervention of surface phenomena. 



We may now consider two syntheses in which there is little or no doubt 

 about the raw materials or some of the chemical reactions involved. These 

 are the production of glycogen and of proteins. 



Glycogen was first isolated in 1857 by Claude Bernard and a little later 

 was analysed by Kekule, who showed that it had the empirical formula 

 CfiHioO,,. It is only recently that its probable structure has been deter- 

 mined. Last year, Haworth, Hirst and Webb succeeded in preparing 

 trimethyl glycogen and proved that on hydrolysis it gives rise to 2.3.6. 

 trimethyl glucose. This observation supported by similar work by Karrer 

 indicates that glycogen is constituted like starch on the basis of continuous 

 maltose units, or what amounts to the same thing, a conjugated chain of 

 a-glucose units. 



It has also been proved that when glycogen breaks down in the liver 

 it gives rise to glucose. Lohmann and also Barbour have succeeded in 

 obtaining glycerol extracts of liver and muscle which hydrolyse it, but the 

 product appears to be a trisaccharide and not glucose. No enzyme which 

 by itself hydrolyses glycogen to glucose has yet been obtained from animal 

 tissues. It is of interest that pancreatic and salivary amylase produce 

 isomaltose from glycogen. These results suggest that there may be some 

 configurational difference between glycogen and starch which accounts for 

 their difference in behaviour with diastatic enzymes. Be that as it may, 

 it appears natural to assume that the synthesis of glycogen from glucose 

 in the cell is brought about by the simple reversal of a hydrolysis which 

 may be catalysed by enzymes under appropriate conditions. These 

 conditions have, however, not yet been realised in vitro. The much simpler 

 synthesis by enzyme action of disaccharides from bexoses — the first 



