8 ANALYSIS OF DISTURBANCES OF METABOLISM 



If the test is made for still longer periods, the weight of the body alone, 

 with minute estimation of the energy value of the food, may enable us to 

 recognize the calory requirement. 



Forster demonstrated in persons living under ordinary conditions the 

 food values just sufficient to maintain weight and to enable them to follow 

 their usual occupations. In numerous investigations with larger groups of 

 men (in barracks, in prisons and in almshouses) by an analysis of the food 

 ingested, valuable standards have been established for the amount of food 

 required by healthy persons. If the individual continues as vigorous as usual 

 and his body-weight remains unchanged while on a prescribed diet, the con- 

 clusion is justifiable that the amount of energy contained in the allotment 

 of food is sufficient for the requirements of the body. 



As the metabolism of the body depends upon the needs of all the cells in 

 the body, and represents essentially a process of combustion, it is obvious 

 that the intake of oxygen should also be considered in estimating metabolism 

 in the body. But the estimation of oxygen consumption is not an accurate 

 measure of the total metabolism, because the same amount of oxygen, accord- 

 ing to whether it is utilized for the oxidation of alb'umin, fat or carbohy- 

 drates, corresponds to different quantities of heat; also because one gram of 

 expired carbonic acid, according as it has been formed by combustion of one 

 or another food stuff, corresponds to very different degrees of heat. 



Therefore, only when the nature of the food-materials decomposed in 

 the body remains the same are consumption of oxygen and excretion of car- 

 bonic acid a measure for changes in the entire consumption of products. 



By means of the large respiratory apparatus of Hoppe-Seyler-Tigerstedt, 

 the direct estimation of all the factors of the respiratory metabolism of gases 

 is possible. The apparatus is difficult to manage, however, and the necessarily 

 long stay in the chamber of the person experimented upon makes its use 

 inconvenient; therefore, in the sick but few observations have been made 

 on this plan. 



It is much easier to estimate the absorption of oxygen and the production 

 of carbonic acid with the apparatus of Zuntz and Geppert. In brief experi- 

 ments, trials are usually made by means of a mouth-piece for only five to ten 

 minutes, at most for one hour; the 0, and CO2 in the expired and inspired 

 air and the amount of O2 intake and CO2 excretion per minute are calculated 

 from this. 



To calculate the total 0, consumption for an entire day from these figures 

 would lead to error, on account of the great variation in the respiratory 

 interchange of gases from hour to hour. 



Their reciprocal relation, however, furnishes the respiratory quotient, 

 which gives valuable information regarding the nature of the material de- 

 composed at the time. It approaches the value of 1.0 in carbohydrate com- 

 bustion, while during the combustion of albumin alone it amounts to 0.73, 

 and in combustion of fat to 0.7. 



For the quantitative estimation of the interchanges, the enormous amount 

 of material gathered by Zuntz and his pupils in numerous healthy and sick 

 persons contributes valuable points. In absolute rest of the body, and in the 



