88 2 



METABOLISM. 



are formed. This has, however, been already discussed (p. 750), and 

 will be again referred to later on. 



Glycerin has been found to act in some measure as a fat and 

 carbohydrate-sparer, but not as a proteid-sparer. 1 Of the total 

 amount ingested, from 21 to 37 per cent, is secreted in the urine 

 unaltered, when given in large doses.^ The sparing effect of glycerin 

 on the conversion of liver glycogen into sugar will be subsequently 

 referred to. 



Alcohol. The nutritive value of alcohol has been the subject of 

 considerable discussion, and not a few experiments. Some of these 

 tend to show that in moderate non-poisonous doses it acts as a non- 

 proteid food in diminishing the oxidation of proteid, doubtless by 

 becoming itself oxidised. 3 Its action, however, in this respect is 

 relatively small, and indeed a certain proportion of alcohol ingested 

 is exhaled with the air of respiration. Moreover, in large doses, it 

 may act in the contrary manner, increasing the waste of tissue proteid. 4 

 It cannot, in fact, be doubted that any small production of energy 

 resulting from its oxidation is more than counterbalanced by its 

 deleterious influences as a drug upon the tissue elements, and especially 

 upon those of the nervous system. 



It is of interest, in connection with this subject, to point out that 

 alcohol has been regarded by some physiologists as probably formed 

 at a stage in the metabolism of carbohydrates prior to their complete 

 oxidation, traces of alcohol having been obtained from fresh tissues by 

 distillation with water. 6 



Inorganic substances. Mineral salts, especially chloride of sodium 

 and phosphates of lime and of the alkalies, are essential parts of 

 any diet. The following table from Bunge gives the proportions 



1 I. Munk, Virchow's Archir, Bd. Ixxvi. S. 119 ; Bd. Ixxx. S. 39. 



2 Tschirwinsky, Ztschr. f. BioL, Miinchen, 1880, Bd. xv. ; Arnschink, ibid., 1888, Bd. 

 xxiii. S. 413. 



3 Strassmann, Arch. /. d. ges. PhysioL, Bonn, 1891, Bd. xlix. S. 315. Chittenden 

 (Journ. PhysioL, Cambridge and London, 1892, vol. xii. p. 220), experimenting upon 

 dogs, obtained very little influence on proteid metabolism. For the earlier literature 

 of this question, cf. C. Voit, op. cit., pp. 169 and 415. 



4 Miura, Ztschr. /. klin. Mcd., Berlin, 1892, Bd. xx. S. 137. I. Munk obtained similar 

 results upon dogs (VerhandL d. PhysioL Gesellsch., 1878-79, No. 6 in Arch. f. PhysioL). 



5 Hoppe-Seyler and Rajewsky, Arch. f. d. ges. PhysioL, Bonn, 1875, Bd. xi. S. 

 122. 



