542 METABOLISM 



the growing organism is being stimulated. Females have a lower energy 

 output than males, and the stimulating influence of puberty is less marked 

 in them. 



In round numbers, 40 C. per square meter of surface per hour is the 

 energy output of normal men, a 1.5 per cent deviation being considered 

 as decidedly abnormal. The average metabolism of fat and thin subjects is 

 the same, but that of women is 6.8 per cent lower than that of men. The 

 basal metabolism of a group of men and women between the ages of forty 

 and fifty was 4.3 per cent below the average for the larger group between 

 the ages of twenty and fifty; and that of a group between fifty and sixty 

 years was 11.3 per cent lower. 



Influence of Diseases 



The measurements have been made by the direct method which has just 

 been described, but since the much simpler indirect method (page 554) 

 yields comparable results, it is being adopted for clinical purposes. These 

 results were obtained by making parallel determinations of energy out- 

 put by both methods, in disease as well as in health. Some of the ob- 

 servations that have been made on the energy output in various diseases 

 are as follows: In very severe cases of exophthalmic goiter, heat produc- 

 tion may be increased by 75 per cent over the normal ; in severe cases, by 

 50 per cent. The warmth of the skin and the sweating, which are promi- 

 nent symptoms of this disease, are therefore accounted for by the in- 

 creased elimination of heat, and it is considered possible that the other 

 symptoms would be produced in any normal individual were his metabo- 

 lism maintained for months or years at the high level which it occupies in 

 goiter. In the opposite condition of myxedema, the energy output is 

 markedly reduced, but rises slowly during treatment with thyroid extract, 

 or much more rapidly with the very active thyroid hormone recently iso- 

 lated by Kendall. In diabetes it has often been thought that the rapid 

 emaciation and loss of strength were dependent upon an excited state of 

 metabolism, or a useless burning up of the energy material. The most 

 recent work, however, clearly shows that this is not the case, the basal 

 metabolism as calculated per unit of body surface being within, the limits 

 indicated above. During the starvation treatment the energv output may 

 be much below the normal. In uncompensated cases of cardiorenal dis- 

 ease, there is increased energy output. In pernicious anemia the metabo- 

 lism is normal, although in severe cases there may be an increased demand 

 for oxygen. 



Even at the risk of repetition, it is important to point out that in all 

 these diseases the energy output is the same whether measured directly or 

 by the indirect method about to be described. 



