A HISTORY OF METABOLISM 47 



In herbivora ten volumes of oxygen absorbed result in nine volumes" 

 of carbon dioxid eliminated. In carnivora only six or five volumes carbon 

 dioxid are eliminated (Diilcmg and Despretz). 



With the exception of a small amount of sulphur, hydrogen is the only 

 other combustible substance with which oxygen could combine and it can be 

 regarded as settled that, whereas in the body of an herbivorous animal one- 

 tenth of the oxygen is used to form water, in the body of the carnivorous animal 

 four or five times that quantity are so employed. 



In- the exact analysis of the process of respiration it is evident that the 

 carbon dioxid production is related to water formation and the two cannot be 

 dissociated. It is therefore self-evident that the determination of the quantity 

 of 'carbon dioxid expired by an animal within a given time is not a measure 

 of the respiratory process and that all experiments in which the relation of the 

 food to the total oxygen intake is not considered have only a relative value. 



In starvation it is not alone fat which disappears but also all solids which 

 are capable of solution. In the completely wasted body of the fasting man the 

 muscles become thin and soft, lose their contractility ; all parts of the body which 

 were capable of producing movement have served to protect the rest of the organs 

 of the body from the destroying influence of the atmosphere. Finally the par- 

 ticles of the brain become involved in the oxidation process, delirium, madness 

 and death follow; resistance completely ceases, chemical putrefaction ensues, 

 and all parts of the body unite with the oxygen of the air. 



Liebig speaks of the cleavage of sugar into lactic acid, into alcohol 

 and carbonic acid, and later into butyric acid, hydrogen and carbonic acid. 

 He then remarks: 



No one will deny that such influences are at work not only in the respiratory 

 process but also have a part in the processes which take place in the animal body, 

 and if further investigations demonstrate that the cause of the decomposition 

 of sugar into alcohol and carbonic acid in alcoholic fermentation is dependent 

 on the development of a lower order of vegetation, and that the metabolism 

 of complex molecules with the production of new substances can be caused by 

 contact with certain particles which are in the state of vital movement, it is 

 clear that a pathway has been constructed which leads to a vision of the mysteri- 

 ous processes of nutrition and secretion. 



As to the energy production, he says: 



The lack of a correct viewpoint regarding energy and activity and their 

 relation to natural phenomena, has led people to ascribe the production of animal 

 heat to the nervous system. If one excludes the metabolism within the active 

 nerves, the above proposition would be merely saying that movement would arise 

 from nothing. But out of nothing no power or activity can arise. 



Liebig asks: 



What is the use of fat, butter, milk-sugar, starch, cane-sugar in the diet? 

 Through these non-nitrogenous food-stuifs a certain amount of carbon and in 

 the case of butter a certain amount of carbon and hydrogen are added to the 

 nitrogen-containing materials and form an excess of elementary substances which 

 cannot be used to generate nitrogen- and sulphur-containing substances, which 

 latter are contained preformed in the food. Hardly a doubt can be entertained 



