On the Peroxides of the Radicals of the Organic Acids. 301 



the collective requirements of the human organism than an exclu- 

 sively bread or other vegetable one, the testimony of common ex- 

 perience may be accepted as sufficient evidence. Whatever may 

 I^rove to be the exact explanations of the benefits arising from a 

 mixed animal and vegetable diet, it is at any rate pretty clear, that, 

 independently of any difference in the physical, and perhaps even 

 chemical relations of the nitrogenous compounds, they are essentially 

 connected with the amount, the condition, and the distribution of 

 theya^, in the animal portions of the food. 



Fat is the most concentrated respiratory, and of course fat-storing 

 material also, which our food-stuffs supply. It cannot be doubted 

 that, independently of the mere supply of constituents, the condi- 

 tions of concentration, of digestibility, and of assimilability, of our 

 different foods, must have their share in determining the relative 

 values, for the varying exigences of the system, of substances which, 

 in a more general, or more purely chemical sense, may still justly 

 be looked upon as mutually replaceable. 



By the aid of Chemistry, it may be established, that, in the admix- 

 ture of animal food with bread, the relation (in respiratory and fat- 

 forming capacity) of the non-flesh-formiug to the flesh-forming 

 substances, will be increased; — and further, that in such a mixed diet, 

 the proportion of the non-flesh-forming constituents, which will be 

 in the concentrated form, so to speak, of fat itself, will be consider- 

 ably greater than in bread alone. Common experience also testifies 

 to the fact of advantages so derived. It remains to Physiology to 

 lend her aid, to the full explanation of that which Chemistry and 

 common usage have thus determined. 



" Note on the Formation of the Peroxides of the Radicals of the 

 Organic Acids." By B. C. Brodie, F.R.S. 



The researches of Gerhardt showed the close resemblance which 

 exists between the monobasic organic acids and the metallic protoxides. 

 We have the chloride of acetyle corresponding to the chloride of the 

 metal, and the hydrated and anhydrous acetic acid corresponding to 

 the hydrated and anhydrous oxide. These investigations have been 

 succeeded by others, which have had their origin in the consistent 

 development of these ideas. The following discovery extends and 

 comj)letes these analogies. I have to add a new term to this series, 

 of which hitherto no analogue has existed. This term is the per- 

 oxide of the organic radical, — the body which in the series of acetyle 

 corresponds to the peroxide of hydrogen or barium in the series of 

 the metal. Of these remarkable substances I have prepared two, — the 

 peroxides of benzoyle and of acetyle ; but the method by which these 

 are procured is doubtless of extensive application, and we may con- 

 sider ourselves as in possession of a class of bodies of a new order, 

 the study of which cannot fail greatly to extend our knowledge. 



These peroxides are prepared by the action of the anhydrous acid, 

 or the corresponding chloride, upon the peroxide of barium. It is 

 first necessary to prepare this peroxide in a pure condition. TJiis is 

 effected by precipitation of the solution of the peroxide of barium iu 



