July 7, 1905.] 



SCIENCE. 



I 



of metabolism was unknown, but that the 

 process was one of cleavage of the food 

 molecules into simpler products which could 

 then unite with oxygen. Yeast cells, for 

 example, convert sugar into carbon dioxide 

 and alcohol without the intervention of 

 oxygen. In like manner the first products 

 of the decomposition of fat, sugar and 

 proteid are formed in metabolism through 

 unknoMm causes. Some of these prelimi- 

 nary decomposition substances may unite 

 with oxygen to form carbon dioxide and 

 water, others may be converted into urea, 

 while others under given .circumstances 

 may be synthesized to higher compounds. 

 In any case the absorption of oxygen does 

 not cause metabolism, but rather the 

 amount of the metabolism determines the 

 amount of oxygen to be absorbed. 



The statement is frequently met with in 

 the literature of the subject that such and 

 such a disease is the consequence of defi- 

 cient oxidation power in the tissues. For 

 example, it has recently been stated that 

 alcohol decreases the oxidation power of 

 the liver for uric acid. Such apparent de- 

 crease in oxidation power may be due to 

 the fact that the protoplasm is so altered 

 that the normal oxidizable cleavage prod- 

 ucts of uric acid are not formed and, there- 

 fore, no oxidation can take place. It is 

 not due to lack of oxygen that sugar does 

 not burn in diabetes, or cystin in cystin- 

 uria. There is the normal supply of 

 oxygen present, but the cleavage of these 

 substances into bodies which can unite with 

 oxygen can not be effected, and hence they 

 can not burn. 



There is a difference of opinion as to 

 whether the food substances must first be- 

 come vital integers of the living cell, or 

 whether the non-living food materials are 

 metabolized without ever becoming a con- 

 stituent part of the living protoplasm. 



Pfliiger holds the former view that incor- 

 poration of nutritive matter with the liv- 



ing substance is essential to its metabolism. 

 He conceives that living proteid may con- 

 tain the labile cyanogen group in contrast 

 with dead proteid which contains the amino 

 group. He illustrates this by Wohler's 

 classic experiment of the easy conversion 

 of ammonium cyanate into urea. 

 NH40CN= (NH„),CO 



Voit's theory is that the living proteid 

 is comparatively stable and that food 

 proteid which becomes the circulating 

 proteid of the blood is carried to the cells 

 and promptly metabolized. The other 

 foodstuffs are also burned without first 

 entering into the composition of the cell. 



A mass of living cells composing the sub- 

 stance of a warm-blooded animal has the 

 same requirement of energy as any similar 

 mass of living cells composing the sub- 

 stance of any other animal of the same size 

 and shape. The reason for the metabolism 

 lies in unknown causes within the cells. 

 Liebig conceived the cause to be due to the 

 swinging motion of the small constituent 

 particles of the cells themselves. If this 

 hypothesis be accepted the vibrations of 

 the cells may be assumed to shatter the 

 proteid molecule into fragments consisting 

 of amino bodies, and to break down fat and 

 sugar into substances of a lower order than 

 themselves. 



The uniformity of the energy require- 

 ment is illustrated by the following table 

 showing the number of calories given off 

 during the twenty-four hours by one 

 square meter of surface in various animals 

 and in man, in the condition of starvation. 



Weight in Cal per 



kilos. sq. m. Surface. 



Man 64 1042 



Pig 128 1078 



Dog 15 1039 



Mouse 0.018 1188 



Diabetic man 54 925 



This illustrates Rubner's law of skin 

 area, which, holds that the metabolism is 



