METABOLISM 27 



due to the direct withdrawal of an ' internal secretion ' 

 (in the wider sense), however, or whether it is the 

 result of the change in disposition which the operation 

 is apt to bring about, is not yet determined. In favour 

 of the former hypothesis are some experiments which 

 seem to show that the administration of ovarian extract 

 is able to counteract the effects of ovariotomy in animals, 

 and to raise the oxygen consumption again to its normal 

 level. Evidence is also accumulating that the develop- 

 ment of the secondary sexual characters, the changes 

 in the uterus which determine menstruation, and the 

 enlargement of the mammary glands during pregnancy, 

 are all the result of chemical influences. 



More and more, then, is it becoming evident that no 

 organ lives to itself alone, but that the chemical changes 

 which take place in each may be of the greatest import- 

 ance to metabolism as a whole, and to the normal 

 interchanges in others. 



7. Influence of Personal Peculiarity. A factor in 

 metabolism which is not often considered by the physio- 

 logist, but which is of the first importance to the 

 physician, is the question of personal peculiarity. 

 Putting aside such agents as differences of age and 

 build, and variations in the amount of body fat, by 

 which differences in the metabolic balance-sheet of 

 individuals can be explained, is there any reason to 

 suppose that the activity of metabolism is greater in 

 some persons than in others? As regards the quali- 

 tative side of metabolism, we shall see that individual 

 peculiarities are not only possible, but can actually be 

 proved to occur; but even as regards the total turn- 



