PREVIOUS INVESTIGATIONS. 13 



PREVIOUS INVESTIGATIONS ON METABOLISM WITH 

 UNDERNUTRITION. 



Many of the researches on undernutrition in the earlier literature 

 were made with animals, and some were carried out under pathological 

 conditions. In collecting data regarding the previous investigations on 

 undernutrition, the studies dealing solely with the loss of nitrogen have 

 been purposely omitted, for only in rare instances have there been 

 satisfactory determinations of the balance of nitrogen intake and out- 

 put for indicating a true gain or loss to the body. The total nitrogen 

 outgo, i. e., the nitrogen in the urine and feces, may be accurately 

 determined without extraordinary analytical procedure, but this tells 

 only half the story and must be supplemented by data regarding the 

 intake. The difficulty of sampling and analyzing mixed diets to secure 

 the total nitrogen of intake is obvious; computed values have, at best, 

 but little significance. Moreover, the nitrogen data are in many of the 

 studies compUcated by distinct pathological conditions, thus excluding 

 them from special consideration in a study of the influence of under- 

 nutrition on normal healthy people. It seems best, therefore, to dis- 

 regard the literature bearing upon the subject of the loss of nitrogen due 

 to undernutrition and to confine the discussion of the previous findings 

 solely to the influence of undernutrition upon the gaseous metabolism. 



Pettenkofer and Voit, 1871. — The importance of studying animals in 

 different stages of nutrition was early recognized by Pettenkofer and 

 Voit,^ who made observations in which 500 to 2,500 grams of meat were 

 fed daily to a dog weighing approximately 35 kg. The smaller portion 

 of food, which corresponds more specifically to undernutrition, was 

 continued for approximately 6 weeks. At first sight it appears as if 

 an experiment of this type would throw definite light upon the demands 

 of the body while on a low nutritional plane. The experimental tech- 

 nique, however, which unfortunately was followed by a number of 

 later observers, involved feeding the animal with meat, placing it at 

 once inside the respiration chamber, and then making observations 

 on the respiratory products in 24-hour periods. It is to be regretted 

 that the excellent method frequently employed by Pettenkofer and 

 Voit of separating their experimental period into day and night periods 

 was not here used, for it is undoubtedly true that during the first hours 

 of the day the metabolism was greatly stimulated by the ingestion of 

 meat, the stimulation being approximately proportional to the amounts 

 of meat ingested. The metabolism as measured, therefore, was not 

 basal metaboUsm, but basal metabolism plus the stimulus of meat. 

 The authors note that there was a distinct falling off in the metabolism 

 when the smaller quantities of meat were given, 500 grams of meat 



^ Pettenkofer and Voit, Zeitschr. f. Biol., 1871, 7, p. 433. 



