THE PHYSIOLOGY OF ALIMENTATION. 545 



form. The doctrine of Liebig, reduced to this fundamental idea, merits 

 survival. Accessory errors compressed its ruin. 



Some years later the celebrated chemist and physiologist of Munich, 

 C. Yoit, revived this doctrine in a more pronounced form. According 

 to him nearly the whole albuminoid aliment was consumed directly in 

 the blood. He interpreted certain experiments upon the utilization of 

 nitrogenous aliments by supposing that these substances when intro- 

 duced into the blood by digestive processes were divided into two por- 

 tions. One very small portion incorporated itself in the living organism 

 and passed to the state of " organic albumen." The remainder was 

 mixed with the blood and lymph, and suffered direct combustion, this 

 being the circulating albumen. In this doctrine the tissues were 

 regarded as nearly stable, only the organic liquids being subject to 

 nutritive metabolism. The accelerated evolution regarded as excep- 

 tional in the doctrine of energetics, was looked upon as the rule by C. 

 Voit. Pfliiger and the Bonn school have corrected this abusive exag- 

 geration. 



The fact, long known, that the consumption of oxygen is notably 

 augmented (to as much as five times its usual value) after eating, is 

 favorable to the supposition that some nutritive substances are absorbed 

 and pass into the blood, to be immediately oxidized and destroyed at 

 once. To be sure some experiments of Zuntz and von Mering are con- 

 trary to this view, for they injected oxidizable substances into the 

 blood vessels without discovering immediate oxidation. But on the 

 other hand, more favorable results of such experiments have been 

 known. 



If the accelerated evolution of the ordinary aliment is thus uncertain 

 it seems that there is undoubtedly a special category of pure thermo- 

 gens, such as alcohol and the acids of fruit. When alcohol is taken in 

 moderate doses about a tenth of the quantity absorbed is taken up by 

 the living elements. The remainder is " the alcohol of circulation" 

 which is directly oxidized in the blood and the lymph, without inter- 

 vening in the vital operations other than by the heat which it produces. 

 According to the theory of energetics such substances are not true 

 aliments, since their potential energy is not transformed into vital 

 energy, but passes at once to the form of heat. On the other hand 

 some physiologists regard alcohol as a true aliment. In their view 

 everything is an aliment which is transformed in the system into heat, 

 and they measure the nutritive value of a substance by the number of 

 calories it produces. By this measure alcohol would be a superior ali- 

 ment to the carbohydrates and nitrogenous substances. A given 

 quantity of alcohol, a gram for example, is equal from this thermal 

 point of view to 1.66 grams of sugar, to 1.44 grams of albumen, and to 

 0.73 gram of fat. These quantities would be isodynamic. 



This is evidently an extreme view, for experience condemns it. The 

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