38 SCIENCE PROGRESS 



Here we come to the end of our very imperfect knowledge 

 concerning these matters. We are left with the practical cer- 

 tainty that, in muscle, at any rate, if sugar be the source of 

 energy, it yields this energy not by a direct oxidation but by 

 a breakdown followed by oxidations. The former gives rise 

 to the rapid evolution of energy which is necessary for a 

 muscular contraction ; the latter, while evolving more massive 

 supplies of heat, in some unknown way yields energy for 

 winding up the machine again. At the same time it would 

 seem that the sugar molecule is not split while in a free state 

 but while in a complex containing more potential energy than 

 the carbohydrate itself. Unfortunately neither the few avail- 

 able facts concerning what happens in muscle nor any con- 

 siderations that can be based upon them give any hint as to 

 where the pancreatic factor intrudes into this chain of events. 

 There is an almost complete hiatus moreover between our 

 knowledge of muscle as a type of normal active tissue using 

 carbohydrate and our knowledge, such as it is, of the diabetic 

 condition. Confining our attention to one point — the probable 

 significance of lactic acid — it is of interest to know that in the 

 diabetic animal any lactic acid given by the mouth increases 

 the sugar in the urine. This suggests that the transformation 

 of the latter into the former is a reversible one. 



Formation of Fat from Sugar 



Dextrose has other relations in metabolism which I have 

 not yet dealt with. Very interesting is its conversion into 

 galactose, which, as a constituent of the milk-sugar molecule, 

 is formed continuously during the manufacture of milk by 

 the mammary gland. It is also found in the so-called cere- 

 brosides, complexes which can be separated from brain-tissue. 

 Unlike the other isomeric sugars, fructose and mannose, it 

 cannot be produced from dextrose by transformation through 

 a common enol form (supra) and it is very unlikely that the 

 change can be controlled by enzymic action. A tempting 

 view with regard to the occurrence of such purely configurative 

 molecular changes in the body is that of H. E. Armstrong, 

 who conceives that a pre-existing structure in the cell, acting 

 as a templet, moulds the precursor into the required form. 



Dextrose is undoubtedly converted into fat in the body, as 



