FonDS — III MAN NUTRITION. 185 



The increased production of heat after food is taken, due to the processea of 



digestion, the differenl amounts of heat produced by differenl f Is, and related 



questions are spoken of. The author points oul thai the amounl of energj required 



tn digest differenl f Is varies, and that this musl be taken into accounl in coi 



ering their t rue energy value. 



"The food value of a uutrienl as a source of energy to the organism is nol meas- 

 ured by the total energ) which it ran liberate as heal in the body, but by the pari 

 of this energy which is available to the organism for physiological uses. The 

 remainder of the 'fuel value' simply serves to increase the generation of heal in the 

 body, a resull which may be advantageous or the reverse, according to the surround- 

 ing conditions." 



Concerning- the natural feeding of infants, M. Rubneb and 0. Heubneb 

 (Ztschr. Expt. Path. u. Ther., / I 1905), No. t,pp. l ■'■'•'■ '" the experiments reported 

 a healthy infant was under observation for 8 months from birth, and data are recorded 



regarding the a tint of food eaten, the gains in weight, etc. During5days, when 



the ehil'l was 5.5 months old and weighed nearly 10 kg., the income ami outgo of 

 carbon and nitrogen were determined. 



For I days the food consisted entirely of mother's milk. On the fifth day the child 

 was given a tea which furnished so little nutritive material thai this was essentially 

 a fasting period. The composition and energy value of the food and excreta were 

 determined. The respiratory products were measured with a respiration apparatus 

 especially constructed for the experiment-, the total amounts of carbon dioxid and 

 water excreted in 24 hours being calculated from the amounts determined for shorter 

 periods. 



Disregarding the first day of the milk period, the average amounl of nitrogen taken 

 per day was L.99 gm., the am<»nnt excreted in the urine 1.13 gm., and in the Eeces 

 0.4 gm. In other words, there was an average daily gain of 0.46 gin. nitrogen. The 

 daily diet turn i shed 63.7 gm. carbon. The average amount excreted in the urine «;i- 

 1.41 gm., in the U'ce< 2.71 gm., and in the respiratory products 61.68 gm., which lk 

 equivalent to an average daily loss of 2.1 gm. carbon. During the tea or fasting 

 period the diel contained no nitrogen nor carbon. The total amount of nitrogen 

 excreted in the mine was 1.18 gm. In other words, the body lost this amount in 24 

 hours. The urine contained 1.29 gm. carhon and the respiratory products 59.5 gm., 

 i. e., there was a loss of 60.79 gm. 



The authors discuss the gain in nitrogen and the loss of carhon on the experimental 

 days in which food was taken and explain the apparent discrepancy on the basis of 

 changes in the water content of the body. A comparison of the amount consumed 

 and furnished by the oxidation of food materials with the quantities excreted shows 

 that actually there was a considerable gain of water. 



Deducting the energy value of the excretory products from the total amount sup- 

 plied by the food, the authors calculated the amount of energy metabolized per day. 

 which was equivalent to 67.6 calories per kilogram body weight, or L,219 calorie- per 

 Square meter surface area. Examination of the experimental data Bhowed that the 

 body w^r<\ the nitrogen of the diet very economically. 



In connection with the experiments some studies were made of the assimilation of 

 nitrogen «>n a diet of mother's milk as compared with cow's milk. It was calculated 



that in the case of mother's milk 0.135 to 0.161 gm. nitrogen in the form of true pro- 

 tein was required per kilogram body weight as compared with 0.530 gm. nitrogen in 

 the case of cow's milk. On the basis of the experimental data the amount of nitrogen 

 required is discussed with reference to the diet of both infants and adults, and the 

 fact noted that the quantity may he small provided the energy value of the diet is 

 sufficiently high. 



Concerning the mechanism of stomach digestion, 1'. < . ia' rzNEB - Arch. Physiol. 

 [Pfluger], 106 (1905), No. 10-12, pp. 468-522, figs. IS).— In experiment- undertaken 



