FOODS — HUMAN NTTTRITIOIT. 1151 



jilbuniin (about 2 gni. por liter boinjj; present), iir^\-i, animoninm salts, phos- 

 phates, siilpiiates. flilorids, potassium, silica, eto. The Mediterranean oyster 

 liiiuor contained a larjrer ([uantity of orj^anic material than tliat of oysters from 

 I lie (x-i-an. 



Experiments on the metabolism of matter and energy in the human 

 body, 1903-1904, F. (i. IJk.nkdk r and U. I). Milnkk ( T. >S. Ihpl. .\<ir.. Office 

 K.vpi. >St(ts. linl. rio. pp. .i.i'i. pJx. J. fi(/s. //). — Like the experiments reported in 

 earlier bulletins (E. S. 11., 15. p. <iOS) those here described furnish important 

 (lata regarding the transformations of ni;itter and energy in the body, the de- 

 mands of the liody for mitriment, the effect of muscular work ui>on such de- 

 mands, and the actual nntrilive \alncs of the different kinds of food materials 

 and tlieir ingredients. These experiments differ materially from those pre- 

 viously i-eported, however, in that the resjiir.-ition calorimeter with which they 

 were made has undergone an important modification which i)ermits the direct 

 nieasurement of the amount of oxygen consumed by the subject, thus affording 

 a more ci>mplete balance of income and outgo of matter and energy than has 

 ever been possible hitherto. 



The account of the experiments is i)receded by a description of the respira- 

 tion calorimeter in its i)resent form. As modified, the apparatus is of the 

 <losed-circuit tyjie. Ilie respiratory products (carbon dk)xid and water vapor) 

 jieing removed and fresh oxygen supplied to the continuous ventilating air 

 current. 



Among the questions discussed on the basis of experimental data are the 

 digestibility of food, the metabolism of nitrogen and pi'otein, the elimination of 

 carbon dioxid and watex", heat production, bodily activity and the measurement 

 of nmscular work, fats versus carbohydrates as protectors of i>rotein, iirotein as 

 a source of energy for nuiscular work, the relative efficiency of fats and carbo- 

 liydrates in rations for muscular work, the conservation of energy in the body, 

 and prolilems of ventilation. 



.Vs regards the theory that protein is the source of muscular work the results 

 (.f the investigations reported indicate that with all due allowance for any 

 delay in the excretion of nitrogen resulting from the katabolism of protein 

 induced by severe muscular work, the total probable disintegration is still far 

 from sullicient to supply all the energy for external muscular work. 



.\s regards tlie relative efficiency of fats and carbohydrates in rations for 

 nuiscular work the results, in the authors' opinion, "seem to wai'rant the belief 

 that fats are jjossibly slightly inferior to carbohydrates as sources of energy for 

 nuiscular work." 



The following deductions the authors consider justilied from the data sup- 

 plied regarding ventilation : "An increase in the amount of carbon dioxid present 

 in tlie air is abscdutely without effect on the mental and bodily comfort of the 

 subjects of the exi)eriments. These subjective observations are ]>aralleled by 

 observations on the resjiiratory exchange and heat output, neither of which 

 factors is in ;uiy way affected. The so-called concomitant impurities of the 

 earlier writers were not discovered in this research. The subjects at. no time 

 complained of headache or other discomfort. It is conceivable, to be sure, that 

 the impurities from one individual would have no deleterious effect ui)on the 

 same individual, but might have on another; yet the water condensed from the 

 respired air, which would probably contain large proportions of such impurities 

 if there had been any, when injected into white rats showed no indication what- 

 ever of any \irulent toxic poison; and ... [it seems probable! that the 

 \inusuai control of thermometric and hygrometric conditions of this form of 

 res])iration calorimeter precludes conditions of temperature and Immidity 

 ordinarily present in poorly ventilated rooms." 



