BALANCE FOR WEIGHING SUBJECT. 93 



BALANCE FOR WEIGHING SUBJECT. 



The loss or gain in body-weight has always been taken as indicating the 

 nature of body condition, a loss usually indicating that there is a loss of 

 body substance and a gain the reverse. In experiments in which a delicate 

 balance between the income and outgo is maintained, as in these experi- 

 ments, it is of special interest to compare the losses in weight as determined 

 by the balance with the calculated metabolism of material and thus obtain 

 a check on the computation of the whole process of metabolism. Since the 

 days of Sanctorius the loss of weight of the body from period to period has 

 been of special interest. The most recent contribution to these investiga- 

 tions is that of the balance described by Lombard,* in which the body- 

 weight is recorded graphically from moment to moment with an extra- 

 ordinarily sensitive balance. 



In connection with the experiments here described, however, the weighing 

 with the balance has a special significance, in that it is possible to have an 

 indirect determination of the oxygen consumption. As pointed out by 

 Pettenkofer and Voit, if the weight of the excretions and the loss in body- 

 weight are taken into consideration, the difference between the weight of the 

 excretions and the loss in body-weight should be the weight of the oxygen 

 absorbed. With this apparatus we are able to determine the water- vapor, 

 the carbon-dioxide excretion, and the weight of the urine and feces when 

 passed. If there is an accurate determination of the body-weight from 

 hour to hour, this should give the data for computing exactly the oxygen 

 consumption. Moreover, we have the direct determination of oxygen with 

 which the indirect method can be compared. 



In the earlier apparatus this comparison was by no means as satisfactory 

 as was desired. The balance there used was sensitive only to 2 grams, the 

 experiments were long (24 hours or more), and it seemed to be absolutely 

 impossible, even by exerting the utmost precaution, to secure the body- 

 weight of the subject each day with exactly the same clothing and acces- 

 sories. Furthermore, where there is a constant change in body-weight 

 amounting to 0.5 gram or more per minute, it is obvious that the weighing 

 should be done at exactly the same moment from day to day. It is seen, 

 therefore, that the comparison with the direct oxygen determination is in 

 reality an investigation by itself, involving the most accurate measurements 

 and the most painstaking development of routine. 



With the hope of contributing materially to our knowledge regarding the 

 indirect determination of oxygen, the special form of balance shown in 

 fig. 9 was installed above the chair calorimeter. This balance is extremely 



* W. P. Lombard: A method of recording changes in body-weight which occur 

 within short intervals of time. The Journal of the American Medical Associa- 

 tion, vol. 47, p. 1790. (1906.) 



